target/linux/ath79/patches-4.19/0061-tty-serial-ar933x-uart-rs485-gpio.patch

   1 From patchwork Fri Feb 21 21:23:31 2020
   2 Content-Type: text/plain; charset="utf-8"
   3 MIME-Version: 1.0
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   5 X-Patchwork-Submitter: Daniel Golle <daniel@makrotopia.org>
   6 X-Patchwork-Id: 1198835
   7 Date: Fri, 21 Feb 2020 22:23:31 +0100
   8 From: Daniel Golle <daniel@makrotopia.org>
   9 To: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
  10 Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
  11  Jiri Slaby <jslaby@suse.com>, Petr =?utf-8?q?=C5=A0tetiar?= <ynezz@true.cz>,
  12  Chuanhong Guo <gch981213@gmail.com>, Piotr Dymacz <pepe2k@gmail.com>
  13 Subject: [PATCH v2] serial: ar933x_uart: add RS485 support
  14 Message-ID: <20200221212331.GA21467@makrotopia.org>
  15 MIME-Version: 1.0
  16 Content-Disposition: inline
  17 Sender: linux-kernel-owner@vger.kernel.org
  18 Precedence: bulk
  19 List-ID: <linux-kernel.vger.kernel.org>
  20 X-Mailing-List: linux-kernel@vger.kernel.org
  21
  22 Emulate half-duplex operation and use mctrl_gpio to add support for
  23 RS485 tranceiver with transmit/receive switch hooked to RTS GPIO line.
  24 This is needed to make use of the RS485 port found on Teltonika RUT955.
  25
  26 Signed-off-by: Daniel Golle <daniel@makrotopia.org>
  27 ---
  28 v2: use bool to indicate ongoing half-duplex send, use it afterwards
  29     to decide whether we've just been in a send operation.
  30
  31  drivers/tty/serial/Kconfig       |   1 +
  32  drivers/tty/serial/ar933x_uart.c | 113 +++++++++++++++++++++++++++++--
  33  2 files changed, 108 insertions(+), 6 deletions(-)
  34
  35 diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
  36 index 52eaac21ff9f..b675924138e0 100644
  37 --- a/drivers/tty/serial/Kconfig
  38 +++ b/drivers/tty/serial/Kconfig
  39 @@ -1279,6 +1279,7 @@ config SERIAL_AR933X
  40         tristate "AR933X serial port support"
  41         depends on HAVE_CLK && ATH79
  42         select SERIAL_CORE
  43 +       select SERIAL_MCTRL_GPIO if GPIOLIB
  44         help
  45           If you have an Atheros AR933X SOC based board and want to use the
  46           built-in UART of the SoC, say Y to this option.
  47 diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
  48 index ea12f10610b6..7e7f1398019f 100644
  49 --- a/drivers/tty/serial/ar933x_uart.c
  50 +++ b/drivers/tty/serial/ar933x_uart.c
  51 @@ -13,6 +13,7 @@
  52  #include <linux/console.h>
  53  #include <linux/sysrq.h>
  54  #include <linux/delay.h>
  55 +#include <linux/gpio/consumer.h>
  56  #include <linux/platform_device.h>
  57  #include <linux/of.h>
  58  #include <linux/of_platform.h>
  59 @@ -29,6 +30,8 @@
  60
  61  #include <asm/mach-ath79/ar933x_uart.h>
  62
  63 +#include "serial_mctrl_gpio.h"
  64 +
  65  #define DRIVER_NAME "ar933x-uart"
  66
  67  #define AR933X_UART_MAX_SCALE  0xff
  68 @@ -47,6 +50,8 @@ struct ar933x_uart_port {
  69         unsigned int            min_baud;
  70         unsigned int            max_baud;
  71         struct clk              *clk;
  72 +       struct mctrl_gpios      *gpios;
  73 +       struct gpio_desc        *rts_gpiod;
  74  };
  75
  76  static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
  77 @@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
  78         ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  79  }
  80
  81 +static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)
  82 +{
  83 +       up->ier |= AR933X_UART_INT_RX_VALID;
  84 +       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  85 +}
  86 +
  87 +static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)
  88 +{
  89 +       up->ier &= ~AR933X_UART_INT_RX_VALID;
  90 +       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  91 +}
  92 +
  93  static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
  94  {
  95         unsigned int rdata;
  96 @@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
  97
  98  static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
  99  {
 100 -       return TIOCM_CAR;
 101 +       struct ar933x_uart_port *up =
 102 +               container_of(port, struct ar933x_uart_port, port);
 103 +       int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
 104 +
 105 +       mctrl_gpio_get(up->gpios, &ret);
 106 +
 107 +       return ret;
 108  }
 109
 110  static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 111  {
 112 +       struct ar933x_uart_port *up =
 113 +               container_of(port, struct ar933x_uart_port, port);
 114 +
 115 +       mctrl_gpio_set(up->gpios, mctrl);
 116  }
 117
 118  static void ar933x_uart_start_tx(struct uart_port *port)
 119 @@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct uart_port *port)
 120         ar933x_uart_start_tx_interrupt(up);
 121  }
 122
 123 +static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)
 124 +{
 125 +       unsigned int status;
 126 +       unsigned int timeout = 60000;
 127 +
 128 +       /* Wait up to 60ms for the character(s) to be sent. */
 129 +       do {
 130 +               status = ar933x_uart_read(up, AR933X_UART_CS_REG);
 131 +               if (--timeout == 0)
 132 +                       break;
 133 +               udelay(1);
 134 +       } while (status & AR933X_UART_CS_TX_BUSY);
 135 +
 136 +       if (timeout == 0)
 137 +               dev_err(up->port.dev, "waiting for TX timed out\n");
 138 +}
 139 +
 140 +static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)
 141 +{
 142 +       unsigned int status;
 143 +
 144 +       /* clear RX_VALID interrupt */
 145 +       ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);
 146 +
 147 +       /* remove characters from the RX FIFO */
 148 +       do {
 149 +               ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);
 150 +               status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
 151 +       } while (status & AR933X_UART_DATA_RX_CSR);
 152 +}
 153 +
 154  static void ar933x_uart_stop_tx(struct uart_port *port)
 155  {
 156         struct ar933x_uart_port *up =
 157 @@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct uart_port *port)
 158         struct ar933x_uart_port *up =
 159                 container_of(port, struct ar933x_uart_port, port);
 160
 161 -       up->ier &= ~AR933X_UART_INT_RX_VALID;
 162 -       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
 163 +       ar933x_uart_stop_rx_interrupt(up);
 164  }
 165
 166  static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
 167 @@ -336,11 +393,20 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
 168  static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
 169  {
 170         struct circ_buf *xmit = &up->port.state->xmit;
 171 +       struct serial_rs485 *rs485conf = &up->port.rs485;
 172         int count;
 173 +       bool half_duplex_send = false;
 174
 175         if (uart_tx_stopped(&up->port))
 176                 return;
 177
 178 +       if ((rs485conf->flags & SER_RS485_ENABLED) &&
 179 +           (up->port.x_char || !uart_circ_empty(xmit))) {
 180 +               ar933x_uart_stop_rx_interrupt(up);
 181 +               gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));
 182 +               half_duplex_send = true;
 183 +       }
 184 +
 185         count = up->port.fifosize;
 186         do {
 187                 unsigned int rdata;
 188 @@ -368,8 +434,14 @@ static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
 189         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 190                 uart_write_wakeup(&up->port);
 191
 192 -       if (!uart_circ_empty(xmit))
 193 +       if (!uart_circ_empty(xmit)) {
 194                 ar933x_uart_start_tx_interrupt(up);
 195 +       } else if (half_duplex_send) {
 196 +               ar933x_uart_wait_tx_complete(up);
 197 +               ar933x_uart_rx_flush(up);
 198 +               ar933x_uart_start_rx_interrupt(up);
 199 +               gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));
 200 +       }
 201  }
 202
 203  static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
 204 @@ -427,8 +499,7 @@ static int ar933x_uart_startup(struct uart_port *port)
 205                 AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);
 206
 207         /* Enable RX interrupts */
 208 -       up->ier = AR933X_UART_INT_RX_VALID;
 209 -       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
 210 +       ar933x_uart_start_rx_interrupt(up);
 211
 212         spin_unlock_irqrestore(&up->port.lock, flags);
 213
 214 @@ -511,6 +582,21 @@ static const struct uart_ops ar933x_uart_ops = {
 215         .verify_port    = ar933x_uart_verify_port,
 216  };
 217
 218 +static int ar933x_config_rs485(struct uart_port *port,
 219 +                               struct serial_rs485 *rs485conf)
 220 +{
 221 +       struct ar933x_uart_port *up =
 222 +               container_of(port, struct ar933x_uart_port, port);
 223 +
 224 +       if ((rs485conf->flags & SER_RS485_ENABLED) &&
 225 +           !up->rts_gpiod) {
 226 +               dev_err(port->dev, "RS485 needs rts-gpio\n");
 227 +               return 1;
 228 +       }
 229 +       port->rs485 = *rs485conf;
 230 +       return 0;
 231 +}
 232 +
 233  #ifdef CONFIG_SERIAL_AR933X_CONSOLE
 234  static struct ar933x_uart_port *
 235  ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
 236 @@ -680,6 +766,8 @@ static int ar933x_uart_probe(struct platform_device *pdev)
 237                 goto err_disable_clk;
 238         }
 239
 240 +       uart_get_rs485_mode(&pdev->dev, &port->rs485);
 241 +
 242         port->mapbase = mem_res->start;
 243         port->line = id;
 244         port->irq = irq_res->start;
 245 @@ -690,6 +778,7 @@ static int ar933x_uart_probe(struct platform_device *pdev)
 246         port->regshift = 2;
 247         port->fifosize = AR933X_UART_FIFO_SIZE;
 248         port->ops = &ar933x_uart_ops;
 249 +       port->rs485_config = ar933x_config_rs485;
 250
 251         baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
 252         up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
 253 @@ -697,6 +786,18 @@ static int ar933x_uart_probe(struct platform_device *pdev)
 254         baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
 255         up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
 256
 257 +       up->gpios = mctrl_gpio_init(port, 0);
 258 +       if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
 259 +               return PTR_ERR(up->gpios);
 260 +
 261 +       up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);
 262 +
 263 +       if ((port->rs485.flags & SER_RS485_ENABLED) &&
 264 +           !up->rts_gpiod) {
 265 +               dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
 266 +               port->rs485.flags &= ~SER_RS485_ENABLED;
 267 +       }
 268 +
 269  #ifdef CONFIG_SERIAL_AR933X_CONSOLE
 270         ar933x_console_ports[up->port.line] = up;
 271  #endif