drivers/tty/serial/8250/8250_mtk.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Mediatek 8250 driver.
   4  *
   5  * Copyright (c) 2014 MundoReader S.L.
   6  * Author: Matthias Brugger <matthias.bgg@gmail.com>
   7  */
   8 #include <linux/clk.h>
   9 #include <linux/io.h>
  10 #include <linux/module.h>
  11 #include <linux/of_irq.h>
  12 #include <linux/of_platform.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/pm_runtime.h>
  15 #include <linux/serial_8250.h>
  16 #include <linux/serial_reg.h>
  17
  18 #include "8250.h"
  19
  20 #define UART_MTK_HIGHS          0x09    /* Highspeed register */
  21 #define UART_MTK_SAMPLE_COUNT   0x0a    /* Sample count register */
  22 #define UART_MTK_SAMPLE_POINT   0x0b    /* Sample point register */
  23 #define MTK_UART_RATE_FIX       0x0d    /* UART Rate Fix Register */
  24
  25 struct mtk8250_data {
  26         int                     line;
  27         struct clk              *uart_clk;
  28         struct clk              *bus_clk;
  29 };
  30
  31 static void
  32 mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
  33                         struct ktermios *old)
  34 {
  35         struct uart_8250_port *up = up_to_u8250p(port);
  36         unsigned long flags;
  37         unsigned int baud, quot;
  38
  39         serial8250_do_set_termios(port, termios, old);
  40
  41         /*
  42          * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
  43          *
  44          * We need to recalcualte the quot register, as the claculation depends
  45          * on the vaule in the highspeed register.
  46          *
  47          * Some baudrates are not supported by the chip, so we use the next
  48          * lower rate supported and update termios c_flag.
  49          *
  50          * If highspeed register is set to 3, we need to specify sample count
  51          * and sample point to increase accuracy. If not, we reset the
  52          * registers to their default values.
  53          */
  54         baud = uart_get_baud_rate(port, termios, old,
  55                                   port->uartclk / 16 / UART_DIV_MAX,
  56                                   port->uartclk);
  57
  58         if (baud <= 115200) {
  59                 serial_port_out(port, UART_MTK_HIGHS, 0x0);
  60                 quot = uart_get_divisor(port, baud);
  61         } else if (baud <= 576000) {
  62                 serial_port_out(port, UART_MTK_HIGHS, 0x2);
  63
  64                 /* Set to next lower baudrate supported */
  65                 if ((baud == 500000) || (baud == 576000))
  66                         baud = 460800;
  67                 quot = DIV_ROUND_UP(port->uartclk, 4 * baud);
  68         } else {
  69                 serial_port_out(port, UART_MTK_HIGHS, 0x3);
  70                 quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
  71         }
  72
  73         /*
  74          * Ok, we're now changing the port state.  Do it with
  75          * interrupts disabled.
  76          */
  77         spin_lock_irqsave(&port->lock, flags);
  78
  79         /* set DLAB we have cval saved in up->lcr from the call to the core */
  80         serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
  81         serial_dl_write(up, quot);
  82
  83         /* reset DLAB */
  84         serial_port_out(port, UART_LCR, up->lcr);
  85
  86         if (baud > 460800) {
  87                 unsigned int tmp;
  88
  89                 tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
  90                 serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
  91                 serial_port_out(port, UART_MTK_SAMPLE_POINT,
  92                                         (tmp - 2) >> 1);
  93         } else {
  94                 serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
  95                 serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
  96         }
  97
  98         spin_unlock_irqrestore(&port->lock, flags);
  99         /* Don't rewrite B0 */
 100         if (tty_termios_baud_rate(termios))
 101                 tty_termios_encode_baud_rate(termios, baud, baud);
 102 }
 103
 104 static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
 105 {
 106         struct mtk8250_data *data = dev_get_drvdata(dev);
 107
 108         clk_disable_unprepare(data->uart_clk);
 109         clk_disable_unprepare(data->bus_clk);
 110
 111         return 0;
 112 }
 113
 114 static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
 115 {
 116         struct mtk8250_data *data = dev_get_drvdata(dev);
 117         int err;
 118
 119         err = clk_prepare_enable(data->uart_clk);
 120         if (err) {
 121                 dev_warn(dev, "Can't enable clock\n");
 122                 return err;
 123         }
 124
 125         err = clk_prepare_enable(data->bus_clk);
 126         if (err) {
 127                 dev_warn(dev, "Can't enable bus clock\n");
 128                 return err;
 129         }
 130
 131         return 0;
 132 }
 133
 134 static void
 135 mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
 136 {
 137         if (!state)
 138                 pm_runtime_get_sync(port->dev);
 139
 140         serial8250_do_pm(port, state, old);
 141
 142         if (state)
 143                 pm_runtime_put_sync_suspend(port->dev);
 144 }
 145
 146 static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
 147                            struct mtk8250_data *data)
 148 {
 149         data->uart_clk = devm_clk_get(&pdev->dev, "baud");
 150         if (IS_ERR(data->uart_clk)) {
 151                 /*
 152                  * For compatibility with older device trees try unnamed
 153                  * clk when no baud clk can be found.
 154                  */
 155                 data->uart_clk = devm_clk_get(&pdev->dev, NULL);
 156                 if (IS_ERR(data->uart_clk)) {
 157                         dev_warn(&pdev->dev, "Can't get uart clock\n");
 158                         return PTR_ERR(data->uart_clk);
 159                 }
 160
 161                 return 0;
 162         }
 163
 164         data->bus_clk = devm_clk_get(&pdev->dev, "bus");
 165         return PTR_ERR_OR_ZERO(data->bus_clk);
 166 }
 167
 168 static int mtk8250_probe(struct platform_device *pdev)
 169 {
 170         struct uart_8250_port uart = {};
 171         struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 172         struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 173         struct mtk8250_data *data;
 174         int err;
 175
 176         if (!regs || !irq) {
 177                 dev_err(&pdev->dev, "no registers/irq defined\n");
 178                 return -EINVAL;
 179         }
 180
 181         uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
 182                                          resource_size(regs));
 183         if (!uart.port.membase)
 184                 return -ENOMEM;
 185
 186         data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
 187         if (!data)
 188                 return -ENOMEM;
 189
 190         if (pdev->dev.of_node) {
 191                 err = mtk8250_probe_of(pdev, &uart.port, data);
 192                 if (err)
 193                         return err;
 194         } else
 195                 return -ENODEV;
 196
 197         spin_lock_init(&uart.port.lock);
 198         uart.port.mapbase = regs->start;
 199         uart.port.irq = irq->start;
 200         uart.port.pm = mtk8250_do_pm;
 201         uart.port.type = PORT_16550;
 202         uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
 203         uart.port.dev = &pdev->dev;
 204         uart.port.iotype = UPIO_MEM32;
 205         uart.port.regshift = 2;
 206         uart.port.private_data = data;
 207         uart.port.set_termios = mtk8250_set_termios;
 208         uart.port.uartclk = clk_get_rate(data->uart_clk);
 209
 210         /* Disable Rate Fix function */
 211         writel(0x0, uart.port.membase +
 212                         (MTK_UART_RATE_FIX << uart.port.regshift));
 213
 214         platform_set_drvdata(pdev, data);
 215
 216         pm_runtime_enable(&pdev->dev);
 217         if (!pm_runtime_enabled(&pdev->dev)) {
 218                 err = mtk8250_runtime_resume(&pdev->dev);
 219                 if (err)
 220                         return err;
 221         }
 222
 223         data->line = serial8250_register_8250_port(&uart);
 224         if (data->line < 0)
 225                 return data->line;
 226
 227         return 0;
 228 }
 229
 230 static int mtk8250_remove(struct platform_device *pdev)
 231 {
 232         struct mtk8250_data *data = platform_get_drvdata(pdev);
 233
 234         pm_runtime_get_sync(&pdev->dev);
 235
 236         serial8250_unregister_port(data->line);
 237
 238         pm_runtime_disable(&pdev->dev);
 239         pm_runtime_put_noidle(&pdev->dev);
 240
 241         if (!pm_runtime_status_suspended(&pdev->dev))
 242                 mtk8250_runtime_suspend(&pdev->dev);
 243
 244         return 0;
 245 }
 246
 247 static int __maybe_unused mtk8250_suspend(struct device *dev)
 248 {
 249         struct mtk8250_data *data = dev_get_drvdata(dev);
 250
 251         serial8250_suspend_port(data->line);
 252
 253         return 0;
 254 }
 255
 256 static int __maybe_unused mtk8250_resume(struct device *dev)
 257 {
 258         struct mtk8250_data *data = dev_get_drvdata(dev);
 259
 260         serial8250_resume_port(data->line);
 261
 262         return 0;
 263 }
 264
 265 static const struct dev_pm_ops mtk8250_pm_ops = {
 266         SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
 267         SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
 268                                 NULL)
 269 };
 270
 271 static const struct of_device_id mtk8250_of_match[] = {
 272         { .compatible = "mediatek,mt6577-uart" },
 273         { /* Sentinel */ }
 274 };
 275 MODULE_DEVICE_TABLE(of, mtk8250_of_match);
 276
 277 static struct platform_driver mtk8250_platform_driver = {
 278         .driver = {
 279                 .name           = "mt6577-uart",
 280                 .pm             = &mtk8250_pm_ops,
 281                 .of_match_table = mtk8250_of_match,
 282         },
 283         .probe                  = mtk8250_probe,
 284         .remove                 = mtk8250_remove,
 285 };
 286 module_platform_driver(mtk8250_platform_driver);
 287
 288 #ifdef CONFIG_SERIAL_8250_CONSOLE
 289 static int __init early_mtk8250_setup(struct earlycon_device *device,
 290                                         const char *options)
 291 {
 292         if (!device->port.membase)
 293                 return -ENODEV;
 294
 295         device->port.iotype = UPIO_MEM32;
 296
 297         return early_serial8250_setup(device, NULL);
 298 }
 299
 300 OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup);
 301 #endif
 302
 303 MODULE_AUTHOR("Matthias Brugger");
 304 MODULE_LICENSE("GPL");
 305 MODULE_DESCRIPTION("Mediatek 8250 serial port driver");