drivers/tty/serial/8250/8250_aspeed_vuart.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *  Serial Port driver for Aspeed VUART device
   4  *
   5  *    Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp.
   6  *    Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.
   7  */
   8 #include <linux/device.h>
   9 #include <linux/module.h>
  10 #include <linux/of_address.h>
  11 #include <linux/of_irq.h>
  12 #include <linux/of_platform.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/clk.h>
  16
  17 #include "8250.h"
  18
  19 #define ASPEED_VUART_GCRA               0x20
  20 #define ASPEED_VUART_GCRA_VUART_EN              BIT(0)
  21 #define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5)
  22 #define ASPEED_VUART_GCRB               0x24
  23 #define ASPEED_VUART_GCRB_HOST_SIRQ_MASK        GENMASK(7, 4)
  24 #define ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT       4
  25 #define ASPEED_VUART_ADDRL              0x28
  26 #define ASPEED_VUART_ADDRH              0x2c
  27
  28 struct aspeed_vuart {
  29         struct device           *dev;
  30         void __iomem            *regs;
  31         struct clk              *clk;
  32         int                     line;
  33         struct timer_list       unthrottle_timer;
  34         struct uart_8250_port   *port;
  35 };
  36
  37 /*
  38  * If we fill the tty flip buffers, we throttle the data ready interrupt
  39  * to prevent dropped characters. This timeout defines how long we wait
  40  * to (conditionally, depending on buffer state) unthrottle.
  41  */
  42 static const int unthrottle_timeout = HZ/10;
  43
  44 /*
  45  * The VUART is basically two UART 'front ends' connected by their FIFO
  46  * (no actual serial line in between). One is on the BMC side (management
  47  * controller) and one is on the host CPU side.
  48  *
  49  * It allows the BMC to provide to the host a "UART" that pipes into
  50  * the BMC itself and can then be turned by the BMC into a network console
  51  * of some sort for example.
  52  *
  53  * This driver is for the BMC side. The sysfs files allow the BMC
  54  * userspace which owns the system configuration policy, to specify
  55  * at what IO port and interrupt number the host side will appear
  56  * to the host on the Host <-> BMC LPC bus. It could be different on a
  57  * different system (though most of them use 3f8/4).
  58  */
  59
  60 static ssize_t lpc_address_show(struct device *dev,
  61                                 struct device_attribute *attr, char *buf)
  62 {
  63         struct aspeed_vuart *vuart = dev_get_drvdata(dev);
  64         u16 addr;
  65
  66         addr = (readb(vuart->regs + ASPEED_VUART_ADDRH) << 8) |
  67                 (readb(vuart->regs + ASPEED_VUART_ADDRL));
  68
  69         return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
  70 }
  71
  72 static ssize_t lpc_address_store(struct device *dev,
  73                                  struct device_attribute *attr,
  74                                  const char *buf, size_t count)
  75 {
  76         struct aspeed_vuart *vuart = dev_get_drvdata(dev);
  77         unsigned long val;
  78         int err;
  79
  80         err = kstrtoul(buf, 0, &val);
  81         if (err)
  82                 return err;
  83
  84         writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);
  85         writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);
  86
  87         return count;
  88 }
  89
  90 static DEVICE_ATTR_RW(lpc_address);
  91
  92 static ssize_t sirq_show(struct device *dev,
  93                          struct device_attribute *attr, char *buf)
  94 {
  95         struct aspeed_vuart *vuart = dev_get_drvdata(dev);
  96         u8 reg;
  97
  98         reg = readb(vuart->regs + ASPEED_VUART_GCRB);
  99         reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
 100         reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
 101
 102         return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
 103 }
 104
 105 static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,
 106                           const char *buf, size_t count)
 107 {
 108         struct aspeed_vuart *vuart = dev_get_drvdata(dev);
 109         unsigned long val;
 110         int err;
 111         u8 reg;
 112
 113         err = kstrtoul(buf, 0, &val);
 114         if (err)
 115                 return err;
 116
 117         val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
 118         val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
 119
 120         reg = readb(vuart->regs + ASPEED_VUART_GCRB);
 121         reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
 122         reg |= val;
 123         writeb(reg, vuart->regs + ASPEED_VUART_GCRB);
 124
 125         return count;
 126 }
 127
 128 static DEVICE_ATTR_RW(sirq);
 129
 130 static struct attribute *aspeed_vuart_attrs[] = {
 131         &dev_attr_sirq.attr,
 132         &dev_attr_lpc_address.attr,
 133         NULL,
 134 };
 135
 136 static const struct attribute_group aspeed_vuart_attr_group = {
 137         .attrs = aspeed_vuart_attrs,
 138 };
 139
 140 static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled)
 141 {
 142         u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA);
 143
 144         if (enabled)
 145                 reg |= ASPEED_VUART_GCRA_VUART_EN;
 146         else
 147                 reg &= ~ASPEED_VUART_GCRA_VUART_EN;
 148
 149         writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
 150 }
 151
 152 static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,
 153                                              bool discard)
 154 {
 155         u8 reg;
 156
 157         reg = readb(vuart->regs + ASPEED_VUART_GCRA);
 158
 159         /* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */
 160         if (!discard)
 161                 reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
 162         else
 163                 reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
 164
 165         writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
 166 }
 167
 168 static int aspeed_vuart_startup(struct uart_port *uart_port)
 169 {
 170         struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
 171         struct aspeed_vuart *vuart = uart_8250_port->port.private_data;
 172         int rc;
 173
 174         rc = serial8250_do_startup(uart_port);
 175         if (rc)
 176                 return rc;
 177
 178         aspeed_vuart_set_host_tx_discard(vuart, false);
 179
 180         return 0;
 181 }
 182
 183 static void aspeed_vuart_shutdown(struct uart_port *uart_port)
 184 {
 185         struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);
 186         struct aspeed_vuart *vuart = uart_8250_port->port.private_data;
 187
 188         aspeed_vuart_set_host_tx_discard(vuart, true);
 189
 190         serial8250_do_shutdown(uart_port);
 191 }
 192
 193 static void __aspeed_vuart_set_throttle(struct uart_8250_port *up,
 194                 bool throttle)
 195 {
 196         unsigned char irqs = UART_IER_RLSI | UART_IER_RDI;
 197
 198         up->ier &= ~irqs;
 199         if (!throttle)
 200                 up->ier |= irqs;
 201         serial_out(up, UART_IER, up->ier);
 202 }
 203 static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle)
 204 {
 205         struct uart_8250_port *up = up_to_u8250p(port);
 206         unsigned long flags;
 207
 208         spin_lock_irqsave(&port->lock, flags);
 209         __aspeed_vuart_set_throttle(up, throttle);
 210         spin_unlock_irqrestore(&port->lock, flags);
 211 }
 212
 213 static void aspeed_vuart_throttle(struct uart_port *port)
 214 {
 215         aspeed_vuart_set_throttle(port, true);
 216 }
 217
 218 static void aspeed_vuart_unthrottle(struct uart_port *port)
 219 {
 220         aspeed_vuart_set_throttle(port, false);
 221 }
 222
 223 static void aspeed_vuart_unthrottle_exp(struct timer_list *timer)
 224 {
 225         struct aspeed_vuart *vuart = from_timer(vuart, timer, unthrottle_timer);
 226         struct uart_8250_port *up = vuart->port;
 227
 228         if (!tty_buffer_space_avail(&up->port.state->port)) {
 229                 mod_timer(&vuart->unthrottle_timer,
 230                           jiffies + unthrottle_timeout);
 231                 return;
 232         }
 233
 234         aspeed_vuart_unthrottle(&up->port);
 235 }
 236
 237 /*
 238  * Custom interrupt handler to manage finer-grained flow control. Although we
 239  * have throttle/unthrottle callbacks, we've seen that the VUART device can
 240  * deliver characters faster than the ldisc has a chance to check buffer space
 241  * against the throttle threshold. This results in dropped characters before
 242  * the throttle.
 243  *
 244  * We do this by checking for flip buffer space before RX. If we have no space,
 245  * throttle now and schedule an unthrottle for later, once the ldisc has had
 246  * a chance to drain the buffers.
 247  */
 248 static int aspeed_vuart_handle_irq(struct uart_port *port)
 249 {
 250         struct uart_8250_port *up = up_to_u8250p(port);
 251         unsigned int iir, lsr;
 252         unsigned long flags;
 253         int space, count;
 254
 255         iir = serial_port_in(port, UART_IIR);
 256
 257         if (iir & UART_IIR_NO_INT)
 258                 return 0;
 259
 260         spin_lock_irqsave(&port->lock, flags);
 261
 262         lsr = serial_port_in(port, UART_LSR);
 263
 264         if (lsr & (UART_LSR_DR | UART_LSR_BI)) {
 265                 space = tty_buffer_space_avail(&port->state->port);
 266
 267                 if (!space) {
 268                         /* throttle and schedule an unthrottle later */
 269                         struct aspeed_vuart *vuart = port->private_data;
 270                         __aspeed_vuart_set_throttle(up, true);
 271
 272                         if (!timer_pending(&vuart->unthrottle_timer)) {
 273                                 vuart->port = up;
 274                                 mod_timer(&vuart->unthrottle_timer,
 275                                           jiffies + unthrottle_timeout);
 276                         }
 277
 278                 } else {
 279                         count = min(space, 256);
 280
 281                         do {
 282                                 serial8250_read_char(up, lsr);
 283                                 lsr = serial_in(up, UART_LSR);
 284                                 if (--count == 0)
 285                                         break;
 286                         } while (lsr & (UART_LSR_DR | UART_LSR_BI));
 287
 288                         tty_flip_buffer_push(&port->state->port);
 289                 }
 290         }
 291
 292         serial8250_modem_status(up);
 293         if (lsr & UART_LSR_THRE)
 294                 serial8250_tx_chars(up);
 295
 296         spin_unlock_irqrestore(&port->lock, flags);
 297
 298         return 1;
 299 }
 300
 301 static int aspeed_vuart_probe(struct platform_device *pdev)
 302 {
 303         struct uart_8250_port port;
 304         struct aspeed_vuart *vuart;
 305         struct device_node *np;
 306         struct resource *res;
 307         u32 clk, prop;
 308         int rc;
 309
 310         np = pdev->dev.of_node;
 311
 312         vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);
 313         if (!vuart)
 314                 return -ENOMEM;
 315
 316         vuart->dev = &pdev->dev;
 317         timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0);
 318
 319         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 320         vuart->regs = devm_ioremap_resource(&pdev->dev, res);
 321         if (IS_ERR(vuart->regs))
 322                 return PTR_ERR(vuart->regs);
 323
 324         memset(&port, 0, sizeof(port));
 325         port.port.private_data = vuart;
 326         port.port.membase = vuart->regs;
 327         port.port.mapbase = res->start;
 328         port.port.mapsize = resource_size(res);
 329         port.port.startup = aspeed_vuart_startup;
 330         port.port.shutdown = aspeed_vuart_shutdown;
 331         port.port.throttle = aspeed_vuart_throttle;
 332         port.port.unthrottle = aspeed_vuart_unthrottle;
 333         port.port.status = UPSTAT_SYNC_FIFO;
 334         port.port.dev = &pdev->dev;
 335
 336         rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
 337         if (rc < 0)
 338                 return rc;
 339
 340         if (of_property_read_u32(np, "clock-frequency", &clk)) {
 341                 vuart->clk = devm_clk_get(&pdev->dev, NULL);
 342                 if (IS_ERR(vuart->clk)) {
 343                         dev_warn(&pdev->dev,
 344                                 "clk or clock-frequency not defined\n");
 345                         rc = PTR_ERR(vuart->clk);
 346                         goto err_sysfs_remove;
 347                 }
 348
 349                 rc = clk_prepare_enable(vuart->clk);
 350                 if (rc < 0)
 351                         goto err_sysfs_remove;
 352
 353                 clk = clk_get_rate(vuart->clk);
 354         }
 355
 356         /* If current-speed was set, then try not to change it. */
 357         if (of_property_read_u32(np, "current-speed", &prop) == 0)
 358                 port.port.custom_divisor = clk / (16 * prop);
 359
 360         /* Check for shifted address mapping */
 361         if (of_property_read_u32(np, "reg-offset", &prop) == 0)
 362                 port.port.mapbase += prop;
 363
 364         /* Check for registers offset within the devices address range */
 365         if (of_property_read_u32(np, "reg-shift", &prop) == 0)
 366                 port.port.regshift = prop;
 367
 368         /* Check for fifo size */
 369         if (of_property_read_u32(np, "fifo-size", &prop) == 0)
 370                 port.port.fifosize = prop;
 371
 372         /* Check for a fixed line number */
 373         rc = of_alias_get_id(np, "serial");
 374         if (rc >= 0)
 375                 port.port.line = rc;
 376
 377         port.port.irq = irq_of_parse_and_map(np, 0);
 378         port.port.irqflags = IRQF_SHARED;
 379         port.port.handle_irq = aspeed_vuart_handle_irq;
 380         port.port.iotype = UPIO_MEM;
 381         port.port.type = PORT_16550A;
 382         port.port.uartclk = clk;
 383         port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 384                 | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST;
 385
 386         if (of_property_read_bool(np, "no-loopback-test"))
 387                 port.port.flags |= UPF_SKIP_TEST;
 388
 389         if (port.port.fifosize)
 390                 port.capabilities = UART_CAP_FIFO;
 391
 392         if (of_property_read_bool(np, "auto-flow-control"))
 393                 port.capabilities |= UART_CAP_AFE;
 394
 395         rc = serial8250_register_8250_port(&port);
 396         if (rc < 0)
 397                 goto err_clk_disable;
 398
 399         vuart->line = rc;
 400
 401         aspeed_vuart_set_enabled(vuart, true);
 402         aspeed_vuart_set_host_tx_discard(vuart, true);
 403         platform_set_drvdata(pdev, vuart);
 404
 405         return 0;
 406
 407 err_clk_disable:
 408         clk_disable_unprepare(vuart->clk);
 409         irq_dispose_mapping(port.port.irq);
 410 err_sysfs_remove:
 411         sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
 412         return rc;
 413 }
 414
 415 static int aspeed_vuart_remove(struct platform_device *pdev)
 416 {
 417         struct aspeed_vuart *vuart = platform_get_drvdata(pdev);
 418
 419         del_timer_sync(&vuart->unthrottle_timer);
 420         aspeed_vuart_set_enabled(vuart, false);
 421         serial8250_unregister_port(vuart->line);
 422         sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
 423         clk_disable_unprepare(vuart->clk);
 424
 425         return 0;
 426 }
 427
 428 static const struct of_device_id aspeed_vuart_table[] = {
 429         { .compatible = "aspeed,ast2400-vuart" },
 430         { .compatible = "aspeed,ast2500-vuart" },
 431         { },
 432 };
 433
 434 static struct platform_driver aspeed_vuart_driver = {
 435         .driver = {
 436                 .name = "aspeed-vuart",
 437                 .of_match_table = aspeed_vuart_table,
 438         },
 439         .probe = aspeed_vuart_probe,
 440         .remove = aspeed_vuart_remove,
 441 };
 442
 443 module_platform_driver(aspeed_vuart_driver);
 444
 445 MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>");
 446 MODULE_LICENSE("GPL");
 447 MODULE_DESCRIPTION("Driver for Aspeed VUART device");