drivers/tty/serial/sprd_serial.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2012-2015 Spreadtrum Communications Inc.
   4  */
   5
   6 #include <linux/clk.h>
   7 #include <linux/console.h>
   8 #include <linux/delay.h>
   9 #include <linux/dmaengine.h>
  10 #include <linux/dma-mapping.h>
  11 #include <linux/dma/sprd-dma.h>
  12 #include <linux/io.h>
  13 #include <linux/ioport.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/of.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/serial_core.h>
  19 #include <linux/serial.h>
  20 #include <linux/slab.h>
  21 #include <linux/tty.h>
  22 #include <linux/tty_flip.h>
  23
  24 /* device name */
  25 #define UART_NR_MAX             8
  26 #define SPRD_TTY_NAME           "ttyS"
  27 #define SPRD_FIFO_SIZE          128
  28 #define SPRD_DEF_RATE           26000000
  29 #define SPRD_BAUD_IO_LIMIT      3000000
  30 #define SPRD_TIMEOUT            256000
  31
  32 /* the offset of serial registers and BITs for them */
  33 /* data registers */
  34 #define SPRD_TXD                0x0000
  35 #define SPRD_RXD                0x0004
  36
  37 /* line status register and its BITs  */
  38 #define SPRD_LSR                0x0008
  39 #define SPRD_LSR_OE             BIT(4)
  40 #define SPRD_LSR_FE             BIT(3)
  41 #define SPRD_LSR_PE             BIT(2)
  42 #define SPRD_LSR_BI             BIT(7)
  43 #define SPRD_LSR_TX_OVER        BIT(15)
  44
  45 /* data number in TX and RX fifo */
  46 #define SPRD_STS1               0x000C
  47 #define SPRD_RX_FIFO_CNT_MASK   GENMASK(7, 0)
  48 #define SPRD_TX_FIFO_CNT_MASK   GENMASK(15, 8)
  49
  50 /* interrupt enable register and its BITs */
  51 #define SPRD_IEN                0x0010
  52 #define SPRD_IEN_RX_FULL        BIT(0)
  53 #define SPRD_IEN_TX_EMPTY       BIT(1)
  54 #define SPRD_IEN_BREAK_DETECT   BIT(7)
  55 #define SPRD_IEN_TIMEOUT        BIT(13)
  56
  57 /* interrupt clear register */
  58 #define SPRD_ICLR               0x0014
  59 #define SPRD_ICLR_TIMEOUT       BIT(13)
  60
  61 /* line control register */
  62 #define SPRD_LCR                0x0018
  63 #define SPRD_LCR_STOP_1BIT      0x10
  64 #define SPRD_LCR_STOP_2BIT      0x30
  65 #define SPRD_LCR_DATA_LEN       (BIT(2) | BIT(3))
  66 #define SPRD_LCR_DATA_LEN5      0x0
  67 #define SPRD_LCR_DATA_LEN6      0x4
  68 #define SPRD_LCR_DATA_LEN7      0x8
  69 #define SPRD_LCR_DATA_LEN8      0xc
  70 #define SPRD_LCR_PARITY         (BIT(0) | BIT(1))
  71 #define SPRD_LCR_PARITY_EN      0x2
  72 #define SPRD_LCR_EVEN_PAR       0x0
  73 #define SPRD_LCR_ODD_PAR        0x1
  74
  75 /* control register 1 */
  76 #define SPRD_CTL1               0x001C
  77 #define SPRD_DMA_EN             BIT(15)
  78 #define SPRD_LOOPBACK_EN        BIT(14)
  79 #define RX_HW_FLOW_CTL_THLD     BIT(6)
  80 #define RX_HW_FLOW_CTL_EN       BIT(7)
  81 #define TX_HW_FLOW_CTL_EN       BIT(8)
  82 #define RX_TOUT_THLD_DEF        0x3E00
  83 #define RX_HFC_THLD_DEF         0x40
  84
  85 /* fifo threshold register */
  86 #define SPRD_CTL2               0x0020
  87 #define THLD_TX_EMPTY           0x40
  88 #define THLD_TX_EMPTY_SHIFT     8
  89 #define THLD_RX_FULL            0x40
  90 #define THLD_RX_FULL_MASK       GENMASK(6, 0)
  91
  92 /* config baud rate register */
  93 #define SPRD_CLKD0              0x0024
  94 #define SPRD_CLKD0_MASK         GENMASK(15, 0)
  95 #define SPRD_CLKD1              0x0028
  96 #define SPRD_CLKD1_MASK         GENMASK(20, 16)
  97 #define SPRD_CLKD1_SHIFT        16
  98
  99 /* interrupt mask status register */
 100 #define SPRD_IMSR               0x002C
 101 #define SPRD_IMSR_RX_FIFO_FULL  BIT(0)
 102 #define SPRD_IMSR_TX_FIFO_EMPTY BIT(1)
 103 #define SPRD_IMSR_BREAK_DETECT  BIT(7)
 104 #define SPRD_IMSR_TIMEOUT       BIT(13)
 105 #define SPRD_DEFAULT_SOURCE_CLK 26000000
 106
 107 #define SPRD_RX_DMA_STEP        1
 108 #define SPRD_RX_FIFO_FULL       1
 109 #define SPRD_TX_FIFO_FULL       0x20
 110 #define SPRD_UART_RX_SIZE       (UART_XMIT_SIZE / 4)
 111
 112 struct sprd_uart_dma {
 113         struct dma_chan *chn;
 114         unsigned char *virt;
 115         dma_addr_t phys_addr;
 116         dma_cookie_t cookie;
 117         u32 trans_len;
 118         bool enable;
 119 };
 120
 121 struct sprd_uart_port {
 122         struct uart_port port;
 123         char name[16];
 124         struct clk *clk;
 125         struct sprd_uart_dma tx_dma;
 126         struct sprd_uart_dma rx_dma;
 127         dma_addr_t pos;
 128         unsigned char *rx_buf_tail;
 129 };
 130
 131 static struct sprd_uart_port *sprd_port[UART_NR_MAX];
 132 static int sprd_ports_num;
 133
 134 static int sprd_start_dma_rx(struct uart_port *port);
 135 static int sprd_tx_dma_config(struct uart_port *port);
 136
 137 static inline unsigned int serial_in(struct uart_port *port,
 138                                      unsigned int offset)
 139 {
 140         return readl_relaxed(port->membase + offset);
 141 }
 142
 143 static inline void serial_out(struct uart_port *port, unsigned int offset,
 144                               int value)
 145 {
 146         writel_relaxed(value, port->membase + offset);
 147 }
 148
 149 static unsigned int sprd_tx_empty(struct uart_port *port)
 150 {
 151         if (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
 152                 return 0;
 153         else
 154                 return TIOCSER_TEMT;
 155 }
 156
 157 static unsigned int sprd_get_mctrl(struct uart_port *port)
 158 {
 159         return TIOCM_DSR | TIOCM_CTS;
 160 }
 161
 162 static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
 163 {
 164         u32 val = serial_in(port, SPRD_CTL1);
 165
 166         if (mctrl & TIOCM_LOOP)
 167                 val |= SPRD_LOOPBACK_EN;
 168         else
 169                 val &= ~SPRD_LOOPBACK_EN;
 170
 171         serial_out(port, SPRD_CTL1, val);
 172 }
 173
 174 static void sprd_stop_rx(struct uart_port *port)
 175 {
 176         struct sprd_uart_port *sp =
 177                 container_of(port, struct sprd_uart_port, port);
 178         unsigned int ien, iclr;
 179
 180         if (sp->rx_dma.enable)
 181                 dmaengine_terminate_all(sp->rx_dma.chn);
 182
 183         iclr = serial_in(port, SPRD_ICLR);
 184         ien = serial_in(port, SPRD_IEN);
 185
 186         ien &= ~(SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT);
 187         iclr |= SPRD_IEN_RX_FULL | SPRD_IEN_BREAK_DETECT;
 188
 189         serial_out(port, SPRD_IEN, ien);
 190         serial_out(port, SPRD_ICLR, iclr);
 191 }
 192
 193 static void sprd_uart_dma_enable(struct uart_port *port, bool enable)
 194 {
 195         u32 val = serial_in(port, SPRD_CTL1);
 196
 197         if (enable)
 198                 val |= SPRD_DMA_EN;
 199         else
 200                 val &= ~SPRD_DMA_EN;
 201
 202         serial_out(port, SPRD_CTL1, val);
 203 }
 204
 205 static void sprd_stop_tx_dma(struct uart_port *port)
 206 {
 207         struct sprd_uart_port *sp =
 208                 container_of(port, struct sprd_uart_port, port);
 209         struct dma_tx_state state;
 210         u32 trans_len;
 211
 212         dmaengine_pause(sp->tx_dma.chn);
 213
 214         dmaengine_tx_status(sp->tx_dma.chn, sp->tx_dma.cookie, &state);
 215         if (state.residue) {
 216                 trans_len = state.residue - sp->tx_dma.phys_addr;
 217                 uart_xmit_advance(port, trans_len);
 218                 dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
 219                                  sp->tx_dma.trans_len, DMA_TO_DEVICE);
 220         }
 221
 222         dmaengine_terminate_all(sp->tx_dma.chn);
 223         sp->tx_dma.trans_len = 0;
 224 }
 225
 226 static int sprd_tx_buf_remap(struct uart_port *port)
 227 {
 228         struct sprd_uart_port *sp =
 229                 container_of(port, struct sprd_uart_port, port);
 230         struct tty_port *tport = &port->state->port;
 231         unsigned char *tail;
 232
 233         sp->tx_dma.trans_len = kfifo_out_linear_ptr(&tport->xmit_fifo, &tail,
 234                         UART_XMIT_SIZE);
 235
 236         sp->tx_dma.phys_addr = dma_map_single(port->dev, tail,
 237                                               sp->tx_dma.trans_len,
 238                                               DMA_TO_DEVICE);
 239         return dma_mapping_error(port->dev, sp->tx_dma.phys_addr);
 240 }
 241
 242 static void sprd_complete_tx_dma(void *data)
 243 {
 244         struct uart_port *port = (struct uart_port *)data;
 245         struct sprd_uart_port *sp =
 246                 container_of(port, struct sprd_uart_port, port);
 247         struct tty_port *tport = &port->state->port;
 248         unsigned long flags;
 249
 250         uart_port_lock_irqsave(port, &flags);
 251         dma_unmap_single(port->dev, sp->tx_dma.phys_addr,
 252                          sp->tx_dma.trans_len, DMA_TO_DEVICE);
 253
 254         uart_xmit_advance(port, sp->tx_dma.trans_len);
 255
 256         if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
 257                 uart_write_wakeup(port);
 258
 259         if (kfifo_is_empty(&tport->xmit_fifo) || sprd_tx_buf_remap(port) ||
 260             sprd_tx_dma_config(port))
 261                 sp->tx_dma.trans_len = 0;
 262
 263         uart_port_unlock_irqrestore(port, flags);
 264 }
 265
 266 static int sprd_uart_dma_submit(struct uart_port *port,
 267                                 struct sprd_uart_dma *ud, u32 trans_len,
 268                                 enum dma_transfer_direction direction,
 269                                 dma_async_tx_callback callback)
 270 {
 271         struct dma_async_tx_descriptor *dma_des;
 272         unsigned long flags;
 273
 274         flags = SPRD_DMA_FLAGS(SPRD_DMA_CHN_MODE_NONE,
 275                                SPRD_DMA_NO_TRG,
 276                                SPRD_DMA_FRAG_REQ,
 277                                SPRD_DMA_TRANS_INT);
 278
 279         dma_des = dmaengine_prep_slave_single(ud->chn, ud->phys_addr, trans_len,
 280                                               direction, flags);
 281         if (!dma_des)
 282                 return -ENODEV;
 283
 284         dma_des->callback = callback;
 285         dma_des->callback_param = port;
 286
 287         ud->cookie = dmaengine_submit(dma_des);
 288         if (dma_submit_error(ud->cookie))
 289                 return dma_submit_error(ud->cookie);
 290
 291         dma_async_issue_pending(ud->chn);
 292
 293         return 0;
 294 }
 295
 296 static int sprd_tx_dma_config(struct uart_port *port)
 297 {
 298         struct sprd_uart_port *sp =
 299                 container_of(port, struct sprd_uart_port, port);
 300         u32 burst = sp->tx_dma.trans_len > SPRD_TX_FIFO_FULL ?
 301                 SPRD_TX_FIFO_FULL : sp->tx_dma.trans_len;
 302         int ret;
 303         struct dma_slave_config cfg = {
 304                 .dst_addr = port->mapbase + SPRD_TXD,
 305                 .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
 306                 .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
 307                 .src_maxburst = burst,
 308         };
 309
 310         ret = dmaengine_slave_config(sp->tx_dma.chn, &cfg);
 311         if (ret < 0)
 312                 return ret;
 313
 314         return sprd_uart_dma_submit(port, &sp->tx_dma, sp->tx_dma.trans_len,
 315                                     DMA_MEM_TO_DEV, sprd_complete_tx_dma);
 316 }
 317
 318 static void sprd_start_tx_dma(struct uart_port *port)
 319 {
 320         struct sprd_uart_port *sp =
 321                 container_of(port, struct sprd_uart_port, port);
 322         struct tty_port *tport = &port->state->port;
 323
 324         if (port->x_char) {
 325                 serial_out(port, SPRD_TXD, port->x_char);
 326                 port->icount.tx++;
 327                 port->x_char = 0;
 328                 return;
 329         }
 330
 331         if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
 332                 sprd_stop_tx_dma(port);
 333                 return;
 334         }
 335
 336         if (sp->tx_dma.trans_len)
 337                 return;
 338
 339         if (sprd_tx_buf_remap(port) || sprd_tx_dma_config(port))
 340                 sp->tx_dma.trans_len = 0;
 341 }
 342
 343 static void sprd_rx_full_thld(struct uart_port *port, u32 thld)
 344 {
 345         u32 val = serial_in(port, SPRD_CTL2);
 346
 347         val &= ~THLD_RX_FULL_MASK;
 348         val |= thld & THLD_RX_FULL_MASK;
 349         serial_out(port, SPRD_CTL2, val);
 350 }
 351
 352 static int sprd_rx_alloc_buf(struct sprd_uart_port *sp)
 353 {
 354         sp->rx_dma.virt = dma_alloc_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
 355                                              &sp->rx_dma.phys_addr, GFP_KERNEL);
 356         if (!sp->rx_dma.virt)
 357                 return -ENOMEM;
 358
 359         return 0;
 360 }
 361
 362 static void sprd_rx_free_buf(struct sprd_uart_port *sp)
 363 {
 364         if (sp->rx_dma.virt)
 365                 dma_free_coherent(sp->port.dev, SPRD_UART_RX_SIZE,
 366                                   sp->rx_dma.virt, sp->rx_dma.phys_addr);
 367         sp->rx_dma.virt = NULL;
 368 }
 369
 370 static int sprd_rx_dma_config(struct uart_port *port, u32 burst)
 371 {
 372         struct sprd_uart_port *sp =
 373                 container_of(port, struct sprd_uart_port, port);
 374         struct dma_slave_config cfg = {
 375                 .src_addr = port->mapbase + SPRD_RXD,
 376                 .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
 377                 .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
 378                 .src_maxburst = burst,
 379         };
 380
 381         return dmaengine_slave_config(sp->rx_dma.chn, &cfg);
 382 }
 383
 384 static void sprd_uart_dma_rx(struct uart_port *port)
 385 {
 386         struct sprd_uart_port *sp =
 387                 container_of(port, struct sprd_uart_port, port);
 388         struct tty_port *tty = &port->state->port;
 389
 390         port->icount.rx += sp->rx_dma.trans_len;
 391         tty_insert_flip_string(tty, sp->rx_buf_tail, sp->rx_dma.trans_len);
 392         tty_flip_buffer_push(tty);
 393 }
 394
 395 static void sprd_uart_dma_irq(struct uart_port *port)
 396 {
 397         struct sprd_uart_port *sp =
 398                 container_of(port, struct sprd_uart_port, port);
 399         struct dma_tx_state state;
 400         enum dma_status status;
 401
 402         status = dmaengine_tx_status(sp->rx_dma.chn,
 403                                      sp->rx_dma.cookie, &state);
 404         if (status == DMA_ERROR)
 405                 sprd_stop_rx(port);
 406
 407         if (!state.residue && sp->pos == sp->rx_dma.phys_addr)
 408                 return;
 409
 410         if (!state.residue) {
 411                 sp->rx_dma.trans_len = SPRD_UART_RX_SIZE +
 412                         sp->rx_dma.phys_addr - sp->pos;
 413                 sp->pos = sp->rx_dma.phys_addr;
 414         } else {
 415                 sp->rx_dma.trans_len = state.residue - sp->pos;
 416                 sp->pos = state.residue;
 417         }
 418
 419         sprd_uart_dma_rx(port);
 420         sp->rx_buf_tail += sp->rx_dma.trans_len;
 421 }
 422
 423 static void sprd_complete_rx_dma(void *data)
 424 {
 425         struct uart_port *port = (struct uart_port *)data;
 426         struct sprd_uart_port *sp =
 427                 container_of(port, struct sprd_uart_port, port);
 428         struct dma_tx_state state;
 429         enum dma_status status;
 430         unsigned long flags;
 431
 432         uart_port_lock_irqsave(port, &flags);
 433
 434         status = dmaengine_tx_status(sp->rx_dma.chn,
 435                                      sp->rx_dma.cookie, &state);
 436         if (status != DMA_COMPLETE) {
 437                 sprd_stop_rx(port);
 438                 uart_port_unlock_irqrestore(port, flags);
 439                 return;
 440         }
 441
 442         if (sp->pos != sp->rx_dma.phys_addr) {
 443                 sp->rx_dma.trans_len =  SPRD_UART_RX_SIZE +
 444                         sp->rx_dma.phys_addr - sp->pos;
 445                 sprd_uart_dma_rx(port);
 446                 sp->rx_buf_tail += sp->rx_dma.trans_len;
 447         }
 448
 449         if (sprd_start_dma_rx(port))
 450                 sprd_stop_rx(port);
 451
 452         uart_port_unlock_irqrestore(port, flags);
 453 }
 454
 455 static int sprd_start_dma_rx(struct uart_port *port)
 456 {
 457         struct sprd_uart_port *sp =
 458                 container_of(port, struct sprd_uart_port, port);
 459         int ret;
 460
 461         if (!sp->rx_dma.enable)
 462                 return 0;
 463
 464         sp->pos = sp->rx_dma.phys_addr;
 465         sp->rx_buf_tail = sp->rx_dma.virt;
 466         sprd_rx_full_thld(port, SPRD_RX_FIFO_FULL);
 467         ret = sprd_rx_dma_config(port, SPRD_RX_DMA_STEP);
 468         if (ret)
 469                 return ret;
 470
 471         return sprd_uart_dma_submit(port, &sp->rx_dma, SPRD_UART_RX_SIZE,
 472                                     DMA_DEV_TO_MEM, sprd_complete_rx_dma);
 473 }
 474
 475 static void sprd_release_dma(struct uart_port *port)
 476 {
 477         struct sprd_uart_port *sp =
 478                 container_of(port, struct sprd_uart_port, port);
 479
 480         sprd_uart_dma_enable(port, false);
 481
 482         if (sp->rx_dma.enable)
 483                 dma_release_channel(sp->rx_dma.chn);
 484
 485         if (sp->tx_dma.enable)
 486                 dma_release_channel(sp->tx_dma.chn);
 487
 488         sp->tx_dma.enable = false;
 489         sp->rx_dma.enable = false;
 490 }
 491
 492 static void sprd_request_dma(struct uart_port *port)
 493 {
 494         struct sprd_uart_port *sp =
 495                 container_of(port, struct sprd_uart_port, port);
 496
 497         sp->tx_dma.enable = true;
 498         sp->rx_dma.enable = true;
 499
 500         sp->tx_dma.chn = dma_request_chan(port->dev, "tx");
 501         if (IS_ERR(sp->tx_dma.chn)) {
 502                 dev_err(port->dev, "request TX DMA channel failed, ret = %ld\n",
 503                         PTR_ERR(sp->tx_dma.chn));
 504                 sp->tx_dma.enable = false;
 505         }
 506
 507         sp->rx_dma.chn = dma_request_chan(port->dev, "rx");
 508         if (IS_ERR(sp->rx_dma.chn)) {
 509                 dev_err(port->dev, "request RX DMA channel failed, ret = %ld\n",
 510                         PTR_ERR(sp->rx_dma.chn));
 511                 sp->rx_dma.enable = false;
 512         }
 513 }
 514
 515 static void sprd_stop_tx(struct uart_port *port)
 516 {
 517         struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
 518                                                  port);
 519         unsigned int ien, iclr;
 520
 521         if (sp->tx_dma.enable) {
 522                 sprd_stop_tx_dma(port);
 523                 return;
 524         }
 525
 526         iclr = serial_in(port, SPRD_ICLR);
 527         ien = serial_in(port, SPRD_IEN);
 528
 529         iclr |= SPRD_IEN_TX_EMPTY;
 530         ien &= ~SPRD_IEN_TX_EMPTY;
 531
 532         serial_out(port, SPRD_IEN, ien);
 533         serial_out(port, SPRD_ICLR, iclr);
 534 }
 535
 536 static void sprd_start_tx(struct uart_port *port)
 537 {
 538         struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
 539                                                  port);
 540         unsigned int ien;
 541
 542         if (sp->tx_dma.enable) {
 543                 sprd_start_tx_dma(port);
 544                 return;
 545         }
 546
 547         ien = serial_in(port, SPRD_IEN);
 548         if (!(ien & SPRD_IEN_TX_EMPTY)) {
 549                 ien |= SPRD_IEN_TX_EMPTY;
 550                 serial_out(port, SPRD_IEN, ien);
 551         }
 552 }
 553
 554 /* The Sprd serial does not support this function. */
 555 static void sprd_break_ctl(struct uart_port *port, int break_state)
 556 {
 557         /* nothing to do */
 558 }
 559
 560 static int handle_lsr_errors(struct uart_port *port,
 561                              u8 *flag,
 562                              unsigned int *lsr)
 563 {
 564         int ret = 0;
 565
 566         /* statistics */
 567         if (*lsr & SPRD_LSR_BI) {
 568                 *lsr &= ~(SPRD_LSR_FE | SPRD_LSR_PE);
 569                 port->icount.brk++;
 570                 ret = uart_handle_break(port);
 571                 if (ret)
 572                         return ret;
 573         } else if (*lsr & SPRD_LSR_PE)
 574                 port->icount.parity++;
 575         else if (*lsr & SPRD_LSR_FE)
 576                 port->icount.frame++;
 577         if (*lsr & SPRD_LSR_OE)
 578                 port->icount.overrun++;
 579
 580         /* mask off conditions which should be ignored */
 581         *lsr &= port->read_status_mask;
 582         if (*lsr & SPRD_LSR_BI)
 583                 *flag = TTY_BREAK;
 584         else if (*lsr & SPRD_LSR_PE)
 585                 *flag = TTY_PARITY;
 586         else if (*lsr & SPRD_LSR_FE)
 587                 *flag = TTY_FRAME;
 588
 589         return ret;
 590 }
 591
 592 static inline void sprd_rx(struct uart_port *port)
 593 {
 594         struct sprd_uart_port *sp = container_of(port, struct sprd_uart_port,
 595                                                  port);
 596         struct tty_port *tty = &port->state->port;
 597         unsigned int lsr, max_count = SPRD_TIMEOUT;
 598         u8 ch, flag;
 599
 600         if (sp->rx_dma.enable) {
 601                 sprd_uart_dma_irq(port);
 602                 return;
 603         }
 604
 605         while ((serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK) &&
 606                max_count--) {
 607                 lsr = serial_in(port, SPRD_LSR);
 608                 ch = serial_in(port, SPRD_RXD);
 609                 flag = TTY_NORMAL;
 610                 port->icount.rx++;
 611
 612                 if (lsr & (SPRD_LSR_BI | SPRD_LSR_PE |
 613                            SPRD_LSR_FE | SPRD_LSR_OE))
 614                         if (handle_lsr_errors(port, &flag, &lsr))
 615                                 continue;
 616                 if (uart_handle_sysrq_char(port, ch))
 617                         continue;
 618
 619                 uart_insert_char(port, lsr, SPRD_LSR_OE, ch, flag);
 620         }
 621
 622         tty_flip_buffer_push(tty);
 623 }
 624
 625 static inline void sprd_tx(struct uart_port *port)
 626 {
 627         u8 ch;
 628
 629         uart_port_tx_limited(port, ch, THLD_TX_EMPTY,
 630                 true,
 631                 serial_out(port, SPRD_TXD, ch),
 632                 ({}));
 633 }
 634
 635 /* this handles the interrupt from one port */
 636 static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
 637 {
 638         struct uart_port *port = dev_id;
 639         unsigned int ims;
 640
 641         uart_port_lock(port);
 642
 643         ims = serial_in(port, SPRD_IMSR);
 644
 645         if (!ims) {
 646                 uart_port_unlock(port);
 647                 return IRQ_NONE;
 648         }
 649
 650         if (ims & SPRD_IMSR_TIMEOUT)
 651                 serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
 652
 653         if (ims & SPRD_IMSR_BREAK_DETECT)
 654                 serial_out(port, SPRD_ICLR, SPRD_IMSR_BREAK_DETECT);
 655
 656         if (ims & (SPRD_IMSR_RX_FIFO_FULL | SPRD_IMSR_BREAK_DETECT |
 657                    SPRD_IMSR_TIMEOUT))
 658                 sprd_rx(port);
 659
 660         if (ims & SPRD_IMSR_TX_FIFO_EMPTY)
 661                 sprd_tx(port);
 662
 663         uart_port_unlock(port);
 664
 665         return IRQ_HANDLED;
 666 }
 667
 668 static void sprd_uart_dma_startup(struct uart_port *port,
 669                                   struct sprd_uart_port *sp)
 670 {
 671         int ret;
 672
 673         sprd_request_dma(port);
 674         if (!(sp->rx_dma.enable || sp->tx_dma.enable))
 675                 return;
 676
 677         ret = sprd_start_dma_rx(port);
 678         if (ret) {
 679                 sp->rx_dma.enable = false;
 680                 dma_release_channel(sp->rx_dma.chn);
 681                 dev_warn(port->dev, "fail to start RX dma mode\n");
 682         }
 683
 684         sprd_uart_dma_enable(port, true);
 685 }
 686
 687 static int sprd_startup(struct uart_port *port)
 688 {
 689         int ret = 0;
 690         unsigned int ien, fc;
 691         unsigned int timeout;
 692         struct sprd_uart_port *sp;
 693         unsigned long flags;
 694
 695         serial_out(port, SPRD_CTL2,
 696                    THLD_TX_EMPTY << THLD_TX_EMPTY_SHIFT | THLD_RX_FULL);
 697
 698         /* clear rx fifo */
 699         timeout = SPRD_TIMEOUT;
 700         while (timeout-- && serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK)
 701                 serial_in(port, SPRD_RXD);
 702
 703         /* clear tx fifo */
 704         timeout = SPRD_TIMEOUT;
 705         while (timeout-- && serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
 706                 cpu_relax();
 707
 708         /* clear interrupt */
 709         serial_out(port, SPRD_IEN, 0);
 710         serial_out(port, SPRD_ICLR, ~0);
 711
 712         /* allocate irq */
 713         sp = container_of(port, struct sprd_uart_port, port);
 714         snprintf(sp->name, sizeof(sp->name), "sprd_serial%d", port->line);
 715
 716         sprd_uart_dma_startup(port, sp);
 717
 718         ret = devm_request_irq(port->dev, port->irq, sprd_handle_irq,
 719                                IRQF_SHARED, sp->name, port);
 720         if (ret) {
 721                 dev_err(port->dev, "fail to request serial irq %d, ret=%d\n",
 722                         port->irq, ret);
 723                 return ret;
 724         }
 725         fc = serial_in(port, SPRD_CTL1);
 726         fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
 727         serial_out(port, SPRD_CTL1, fc);
 728
 729         /* enable interrupt */
 730         uart_port_lock_irqsave(port, &flags);
 731         ien = serial_in(port, SPRD_IEN);
 732         ien |= SPRD_IEN_BREAK_DETECT | SPRD_IEN_TIMEOUT;
 733         if (!sp->rx_dma.enable)
 734                 ien |= SPRD_IEN_RX_FULL;
 735         serial_out(port, SPRD_IEN, ien);
 736         uart_port_unlock_irqrestore(port, flags);
 737
 738         return 0;
 739 }
 740
 741 static void sprd_shutdown(struct uart_port *port)
 742 {
 743         sprd_release_dma(port);
 744         serial_out(port, SPRD_IEN, 0);
 745         serial_out(port, SPRD_ICLR, ~0);
 746         devm_free_irq(port->dev, port->irq, port);
 747 }
 748
 749 static void sprd_set_termios(struct uart_port *port, struct ktermios *termios,
 750                              const struct ktermios *old)
 751 {
 752         unsigned int baud, quot;
 753         unsigned int lcr = 0, fc;
 754         unsigned long flags;
 755
 756         /* ask the core to calculate the divisor for us */
 757         baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
 758
 759         quot = port->uartclk / baud;
 760
 761         /* set data length */
 762         switch (termios->c_cflag & CSIZE) {
 763         case CS5:
 764                 lcr |= SPRD_LCR_DATA_LEN5;
 765                 break;
 766         case CS6:
 767                 lcr |= SPRD_LCR_DATA_LEN6;
 768                 break;
 769         case CS7:
 770                 lcr |= SPRD_LCR_DATA_LEN7;
 771                 break;
 772         case CS8:
 773         default:
 774                 lcr |= SPRD_LCR_DATA_LEN8;
 775                 break;
 776         }
 777
 778         /* calculate stop bits */
 779         lcr &= ~(SPRD_LCR_STOP_1BIT | SPRD_LCR_STOP_2BIT);
 780         if (termios->c_cflag & CSTOPB)
 781                 lcr |= SPRD_LCR_STOP_2BIT;
 782         else
 783                 lcr |= SPRD_LCR_STOP_1BIT;
 784
 785         /* calculate parity */
 786         lcr &= ~SPRD_LCR_PARITY;
 787         termios->c_cflag &= ~CMSPAR;    /* no support mark/space */
 788         if (termios->c_cflag & PARENB) {
 789                 lcr |= SPRD_LCR_PARITY_EN;
 790                 if (termios->c_cflag & PARODD)
 791                         lcr |= SPRD_LCR_ODD_PAR;
 792                 else
 793                         lcr |= SPRD_LCR_EVEN_PAR;
 794         }
 795
 796         uart_port_lock_irqsave(port, &flags);
 797
 798         /* update the per-port timeout */
 799         uart_update_timeout(port, termios->c_cflag, baud);
 800
 801         port->read_status_mask = SPRD_LSR_OE;
 802         if (termios->c_iflag & INPCK)
 803                 port->read_status_mask |= SPRD_LSR_FE | SPRD_LSR_PE;
 804         if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
 805                 port->read_status_mask |= SPRD_LSR_BI;
 806
 807         /* characters to ignore */
 808         port->ignore_status_mask = 0;
 809         if (termios->c_iflag & IGNPAR)
 810                 port->ignore_status_mask |= SPRD_LSR_PE | SPRD_LSR_FE;
 811         if (termios->c_iflag & IGNBRK) {
 812                 port->ignore_status_mask |= SPRD_LSR_BI;
 813                 /*
 814                  * If we're ignoring parity and break indicators,
 815                  * ignore overruns too (for real raw support).
 816                  */
 817                 if (termios->c_iflag & IGNPAR)
 818                         port->ignore_status_mask |= SPRD_LSR_OE;
 819         }
 820
 821         /* flow control */
 822         fc = serial_in(port, SPRD_CTL1);
 823         fc &= ~(RX_HW_FLOW_CTL_THLD | RX_HW_FLOW_CTL_EN | TX_HW_FLOW_CTL_EN);
 824         if (termios->c_cflag & CRTSCTS) {
 825                 fc |= RX_HW_FLOW_CTL_THLD;
 826                 fc |= RX_HW_FLOW_CTL_EN;
 827                 fc |= TX_HW_FLOW_CTL_EN;
 828         }
 829
 830         /* clock divider bit0~bit15 */
 831         serial_out(port, SPRD_CLKD0, quot & SPRD_CLKD0_MASK);
 832
 833         /* clock divider bit16~bit20 */
 834         serial_out(port, SPRD_CLKD1,
 835                    (quot & SPRD_CLKD1_MASK) >> SPRD_CLKD1_SHIFT);
 836         serial_out(port, SPRD_LCR, lcr);
 837         fc |= RX_TOUT_THLD_DEF | RX_HFC_THLD_DEF;
 838         serial_out(port, SPRD_CTL1, fc);
 839
 840         uart_port_unlock_irqrestore(port, flags);
 841
 842         /* Don't rewrite B0 */
 843         if (tty_termios_baud_rate(termios))
 844                 tty_termios_encode_baud_rate(termios, baud, baud);
 845 }
 846
 847 static const char *sprd_type(struct uart_port *port)
 848 {
 849         return "SPX";
 850 }
 851
 852 static void sprd_release_port(struct uart_port *port)
 853 {
 854         /* nothing to do */
 855 }
 856
 857 static int sprd_request_port(struct uart_port *port)
 858 {
 859         return 0;
 860 }
 861
 862 static void sprd_config_port(struct uart_port *port, int flags)
 863 {
 864         if (flags & UART_CONFIG_TYPE)
 865                 port->type = PORT_SPRD;
 866 }
 867
 868 static int sprd_verify_port(struct uart_port *port, struct serial_struct *ser)
 869 {
 870         if (ser->type != PORT_SPRD)
 871                 return -EINVAL;
 872         if (port->irq != ser->irq)
 873                 return -EINVAL;
 874         if (port->iotype != ser->io_type)
 875                 return -EINVAL;
 876         return 0;
 877 }
 878
 879 static void sprd_pm(struct uart_port *port, unsigned int state,
 880                 unsigned int oldstate)
 881 {
 882         struct sprd_uart_port *sup =
 883                 container_of(port, struct sprd_uart_port, port);
 884
 885         switch (state) {
 886         case UART_PM_STATE_ON:
 887                 clk_prepare_enable(sup->clk);
 888                 break;
 889         case UART_PM_STATE_OFF:
 890                 clk_disable_unprepare(sup->clk);
 891                 break;
 892         }
 893 }
 894
 895 #ifdef CONFIG_CONSOLE_POLL
 896 static int sprd_poll_init(struct uart_port *port)
 897 {
 898         if (port->state->pm_state != UART_PM_STATE_ON) {
 899                 sprd_pm(port, UART_PM_STATE_ON, 0);
 900                 port->state->pm_state = UART_PM_STATE_ON;
 901         }
 902
 903         return 0;
 904 }
 905
 906 static int sprd_poll_get_char(struct uart_port *port)
 907 {
 908         while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))
 909                 cpu_relax();
 910
 911         return serial_in(port, SPRD_RXD);
 912 }
 913
 914 static void sprd_poll_put_char(struct uart_port *port, unsigned char ch)
 915 {
 916         while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
 917                 cpu_relax();
 918
 919         serial_out(port, SPRD_TXD, ch);
 920 }
 921 #endif
 922
 923 static const struct uart_ops serial_sprd_ops = {
 924         .tx_empty = sprd_tx_empty,
 925         .get_mctrl = sprd_get_mctrl,
 926         .set_mctrl = sprd_set_mctrl,
 927         .stop_tx = sprd_stop_tx,
 928         .start_tx = sprd_start_tx,
 929         .stop_rx = sprd_stop_rx,
 930         .break_ctl = sprd_break_ctl,
 931         .startup = sprd_startup,
 932         .shutdown = sprd_shutdown,
 933         .set_termios = sprd_set_termios,
 934         .type = sprd_type,
 935         .release_port = sprd_release_port,
 936         .request_port = sprd_request_port,
 937         .config_port = sprd_config_port,
 938         .verify_port = sprd_verify_port,
 939         .pm = sprd_pm,
 940 #ifdef CONFIG_CONSOLE_POLL
 941         .poll_init      = sprd_poll_init,
 942         .poll_get_char  = sprd_poll_get_char,
 943         .poll_put_char  = sprd_poll_put_char,
 944 #endif
 945 };
 946
 947 #ifdef CONFIG_SERIAL_SPRD_CONSOLE
 948 static void wait_for_xmitr(struct uart_port *port)
 949 {
 950         unsigned int status, tmout = 10000;
 951
 952         /* wait up to 10ms for the character(s) to be sent */
 953         do {
 954                 status = serial_in(port, SPRD_STS1);
 955                 if (--tmout == 0)
 956                         break;
 957                 udelay(1);
 958         } while (status & SPRD_TX_FIFO_CNT_MASK);
 959 }
 960
 961 static void sprd_console_putchar(struct uart_port *port, unsigned char ch)
 962 {
 963         wait_for_xmitr(port);
 964         serial_out(port, SPRD_TXD, ch);
 965 }
 966
 967 static void sprd_console_write(struct console *co, const char *s,
 968                                unsigned int count)
 969 {
 970         struct uart_port *port = &sprd_port[co->index]->port;
 971         int locked = 1;
 972         unsigned long flags;
 973
 974         if (port->sysrq)
 975                 locked = 0;
 976         else if (oops_in_progress)
 977                 locked = uart_port_trylock_irqsave(port, &flags);
 978         else
 979                 uart_port_lock_irqsave(port, &flags);
 980
 981         uart_console_write(port, s, count, sprd_console_putchar);
 982
 983         /* wait for transmitter to become empty */
 984         wait_for_xmitr(port);
 985
 986         if (locked)
 987                 uart_port_unlock_irqrestore(port, flags);
 988 }
 989
 990 static int sprd_console_setup(struct console *co, char *options)
 991 {
 992         struct sprd_uart_port *sprd_uart_port;
 993         int baud = 115200;
 994         int bits = 8;
 995         int parity = 'n';
 996         int flow = 'n';
 997
 998         if (co->index >= UART_NR_MAX || co->index < 0)
 999                 co->index = 0;
1000
1001         sprd_uart_port = sprd_port[co->index];
1002         if (!sprd_uart_port || !sprd_uart_port->port.membase) {
1003                 pr_info("serial port %d not yet initialized\n", co->index);
1004                 return -ENODEV;
1005         }
1006
1007         if (options)
1008                 uart_parse_options(options, &baud, &parity, &bits, &flow);
1009
1010         return uart_set_options(&sprd_uart_port->port, co, baud,
1011                                 parity, bits, flow);
1012 }
1013
1014 static struct uart_driver sprd_uart_driver;
1015 static struct console sprd_console = {
1016         .name = SPRD_TTY_NAME,
1017         .write = sprd_console_write,
1018         .device = uart_console_device,
1019         .setup = sprd_console_setup,
1020         .flags = CON_PRINTBUFFER,
1021         .index = -1,
1022         .data = &sprd_uart_driver,
1023 };
1024
1025 static int __init sprd_serial_console_init(void)
1026 {
1027         register_console(&sprd_console);
1028         return 0;
1029 }
1030 console_initcall(sprd_serial_console_init);
1031
1032 #define SPRD_CONSOLE    (&sprd_console)
1033
1034 /* Support for earlycon */
1035 static void sprd_putc(struct uart_port *port, unsigned char c)
1036 {
1037         unsigned int timeout = SPRD_TIMEOUT;
1038
1039         while (timeout-- &&
1040                !(readl(port->membase + SPRD_LSR) & SPRD_LSR_TX_OVER))
1041                 cpu_relax();
1042
1043         writeb(c, port->membase + SPRD_TXD);
1044 }
1045
1046 static void sprd_early_write(struct console *con, const char *s, unsigned int n)
1047 {
1048         struct earlycon_device *dev = con->data;
1049
1050         uart_console_write(&dev->port, s, n, sprd_putc);
1051 }
1052
1053 static int __init sprd_early_console_setup(struct earlycon_device *device,
1054                                            const char *opt)
1055 {
1056         if (!device->port.membase)
1057                 return -ENODEV;
1058
1059         device->con->write = sprd_early_write;
1060         return 0;
1061 }
1062 OF_EARLYCON_DECLARE(sprd_serial, "sprd,sc9836-uart",
1063                     sprd_early_console_setup);
1064
1065 #else /* !CONFIG_SERIAL_SPRD_CONSOLE */
1066 #define SPRD_CONSOLE            NULL
1067 #endif
1068
1069 static struct uart_driver sprd_uart_driver = {
1070         .owner = THIS_MODULE,
1071         .driver_name = "sprd_serial",
1072         .dev_name = SPRD_TTY_NAME,
1073         .major = 0,
1074         .minor = 0,
1075         .nr = UART_NR_MAX,
1076         .cons = SPRD_CONSOLE,
1077 };
1078
1079 static void sprd_remove(struct platform_device *dev)
1080 {
1081         struct sprd_uart_port *sup = platform_get_drvdata(dev);
1082
1083         if (sup) {
1084                 uart_remove_one_port(&sprd_uart_driver, &sup->port);
1085                 sprd_port[sup->port.line] = NULL;
1086                 sprd_rx_free_buf(sup);
1087                 sprd_ports_num--;
1088         }
1089
1090         if (!sprd_ports_num)
1091                 uart_unregister_driver(&sprd_uart_driver);
1092 }
1093
1094 static bool sprd_uart_is_console(struct uart_port *uport)
1095 {
1096         struct console *cons = sprd_uart_driver.cons;
1097
1098         if ((cons && cons->index >= 0 && cons->index == uport->line) ||
1099             of_console_check(uport->dev->of_node, SPRD_TTY_NAME, uport->line))
1100                 return true;
1101
1102         return false;
1103 }
1104
1105 static int sprd_clk_init(struct uart_port *uport)
1106 {
1107         struct clk *clk_uart, *clk_parent;
1108         struct sprd_uart_port *u = container_of(uport, struct sprd_uart_port, port);
1109
1110         clk_uart = devm_clk_get(uport->dev, "uart");
1111         if (IS_ERR(clk_uart)) {
1112                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
1113                          uport->line);
1114                 clk_uart = NULL;
1115         }
1116
1117         clk_parent = devm_clk_get(uport->dev, "source");
1118         if (IS_ERR(clk_parent)) {
1119                 dev_warn(uport->dev, "uart%d can't get source clock\n",
1120                          uport->line);
1121                 clk_parent = NULL;
1122         }
1123
1124         if (!clk_uart || clk_set_parent(clk_uart, clk_parent))
1125                 uport->uartclk = SPRD_DEFAULT_SOURCE_CLK;
1126         else
1127                 uport->uartclk = clk_get_rate(clk_uart);
1128
1129         u->clk = devm_clk_get(uport->dev, "enable");
1130         if (IS_ERR(u->clk)) {
1131                 if (PTR_ERR(u->clk) == -EPROBE_DEFER)
1132                         return -EPROBE_DEFER;
1133
1134                 dev_warn(uport->dev, "uart%d can't get enable clock\n",
1135                         uport->line);
1136
1137                 /* To keep console alive even if the error occurred */
1138                 if (!sprd_uart_is_console(uport))
1139                         return PTR_ERR(u->clk);
1140
1141                 u->clk = NULL;
1142         }
1143
1144         return 0;
1145 }
1146
1147 static int sprd_probe(struct platform_device *pdev)
1148 {
1149         struct resource *res;
1150         struct uart_port *up;
1151         struct sprd_uart_port *sport;
1152         int irq;
1153         int index;
1154         int ret;
1155
1156         index = of_alias_get_id(pdev->dev.of_node, "serial");
1157         if (index < 0 || index >= UART_NR_MAX) {
1158                 dev_err(&pdev->dev, "got a wrong serial alias id %d\n", index);
1159                 return -EINVAL;
1160         }
1161
1162         sport = devm_kzalloc(&pdev->dev, sizeof(*sport), GFP_KERNEL);
1163         if (!sport)
1164                 return -ENOMEM;
1165
1166         up = &sport->port;
1167         up->dev = &pdev->dev;
1168         up->line = index;
1169         up->type = PORT_SPRD;
1170         up->iotype = UPIO_MEM;
1171         up->uartclk = SPRD_DEF_RATE;
1172         up->fifosize = SPRD_FIFO_SIZE;
1173         up->ops = &serial_sprd_ops;
1174         up->flags = UPF_BOOT_AUTOCONF;
1175         up->has_sysrq = IS_ENABLED(CONFIG_SERIAL_SPRD_CONSOLE);
1176
1177         ret = sprd_clk_init(up);
1178         if (ret)
1179                 return ret;
1180
1181         up->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
1182         if (IS_ERR(up->membase))
1183                 return PTR_ERR(up->membase);
1184
1185         up->mapbase = res->start;
1186
1187         irq = platform_get_irq(pdev, 0);
1188         if (irq < 0)
1189                 return irq;
1190         up->irq = irq;
1191
1192         /*
1193          * Allocate one dma buffer to prepare for receive transfer, in case
1194          * memory allocation failure at runtime.
1195          */
1196         ret = sprd_rx_alloc_buf(sport);
1197         if (ret)
1198                 return ret;
1199
1200         if (!sprd_ports_num) {
1201                 ret = uart_register_driver(&sprd_uart_driver);
1202                 if (ret < 0) {
1203                         pr_err("Failed to register SPRD-UART driver\n");
1204                         goto free_rx_buf;
1205                 }
1206         }
1207
1208         sprd_ports_num++;
1209         sprd_port[index] = sport;
1210
1211         ret = uart_add_one_port(&sprd_uart_driver, up);
1212         if (ret)
1213                 goto clean_port;
1214
1215         platform_set_drvdata(pdev, up);
1216
1217         return 0;
1218
1219 clean_port:
1220         sprd_port[index] = NULL;
1221         if (--sprd_ports_num == 0)
1222                 uart_unregister_driver(&sprd_uart_driver);
1223 free_rx_buf:
1224         sprd_rx_free_buf(sport);
1225         return ret;
1226 }
1227
1228 #ifdef CONFIG_PM_SLEEP
1229 static int sprd_suspend(struct device *dev)
1230 {
1231         struct sprd_uart_port *sup = dev_get_drvdata(dev);
1232
1233         uart_suspend_port(&sprd_uart_driver, &sup->port);
1234
1235         return 0;
1236 }
1237
1238 static int sprd_resume(struct device *dev)
1239 {
1240         struct sprd_uart_port *sup = dev_get_drvdata(dev);
1241
1242         uart_resume_port(&sprd_uart_driver, &sup->port);
1243
1244         return 0;
1245 }
1246 #endif
1247
1248 static SIMPLE_DEV_PM_OPS(sprd_pm_ops, sprd_suspend, sprd_resume);
1249
1250 static const struct of_device_id serial_ids[] = {
1251         {.compatible = "sprd,sc9836-uart",},
1252         {}
1253 };
1254 MODULE_DEVICE_TABLE(of, serial_ids);
1255
1256 static struct platform_driver sprd_platform_driver = {
1257         .probe          = sprd_probe,
1258         .remove_new     = sprd_remove,
1259         .driver         = {
1260                 .name   = "sprd_serial",
1261                 .of_match_table = serial_ids,
1262                 .pm     = &sprd_pm_ops,
1263         },
1264 };
1265
1266 module_platform_driver(sprd_platform_driver);
1267
1268 MODULE_LICENSE("GPL v2");
1269 MODULE_DESCRIPTION("Spreadtrum SoC serial driver series");