target/linux/ath79/patches-5.4/0061-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 --- a/drivers/tty/serial/Kconfig
  36 +++ b/drivers/tty/serial/Kconfig
  37 @@ -1279,6 +1279,7 @@ config SERIAL_AR933X
  38         tristate "AR933X serial port support"
  39         depends on HAVE_CLK && ATH79
  40         select SERIAL_CORE
  41 +       select SERIAL_MCTRL_GPIO if GPIOLIB
  42         help
  43           If you have an Atheros AR933X SOC based board and want to use the
  44           built-in UART of the SoC, say Y to this option.
  45 --- a/drivers/tty/serial/ar933x_uart.c
  46 +++ b/drivers/tty/serial/ar933x_uart.c
  47 @@ -13,6 +13,7 @@
  48  #include <linux/console.h>
  49  #include <linux/sysrq.h>
  50  #include <linux/delay.h>
  51 +#include <linux/gpio/consumer.h>
  52  #include <linux/platform_device.h>
  53  #include <linux/of.h>
  54  #include <linux/of_platform.h>
  55 @@ -29,6 +30,8 @@
  56
  57  #include <asm/mach-ath79/ar933x_uart.h>
  58
  59 +#include "serial_mctrl_gpio.h"
  60 +
  61  #define DRIVER_NAME "ar933x-uart"
  62
  63  #define AR933X_UART_MAX_SCALE  0xff
  64 @@ -47,6 +50,8 @@ struct ar933x_uart_port {
  65         unsigned int            min_baud;
  66         unsigned int            max_baud;
  67         struct clk              *clk;
  68 +       struct mctrl_gpios      *gpios;
  69 +       struct gpio_desc        *rts_gpiod;
  70  };
  71
  72  static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
  73 @@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_i
  74         ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  75  }
  76
  77 +static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)
  78 +{
  79 +       up->ier |= AR933X_UART_INT_RX_VALID;
  80 +       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  81 +}
  82 +
  83 +static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)
  84 +{
  85 +       up->ier &= ~AR933X_UART_INT_RX_VALID;
  86 +       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
  87 +}
  88 +
  89  static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
  90  {
  91         unsigned int rdata;
  92 @@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty
  93
  94  static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
  95  {
  96 -       return TIOCM_CAR;
  97 +       struct ar933x_uart_port *up =
  98 +               container_of(port, struct ar933x_uart_port, port);
  99 +       int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
 100 +
 101 +       mctrl_gpio_get(up->gpios, &ret);
 102 +
 103 +       return ret;
 104  }
 105
 106  static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 107  {
 108 +       struct ar933x_uart_port *up =
 109 +               container_of(port, struct ar933x_uart_port, port);
 110 +
 111 +       mctrl_gpio_set(up->gpios, mctrl);
 112  }
 113
 114  static void ar933x_uart_start_tx(struct uart_port *port)
 115 @@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct
 116         ar933x_uart_start_tx_interrupt(up);
 117  }
 118
 119 +static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)
 120 +{
 121 +       unsigned int status;
 122 +       unsigned int timeout = 60000;
 123 +
 124 +       /* Wait up to 60ms for the character(s) to be sent. */
 125 +       do {
 126 +               status = ar933x_uart_read(up, AR933X_UART_CS_REG);
 127 +               if (--timeout == 0)
 128 +                       break;
 129 +               udelay(1);
 130 +       } while (status & AR933X_UART_CS_TX_BUSY);
 131 +
 132 +       if (timeout == 0)
 133 +               dev_err(up->port.dev, "waiting for TX timed out\n");
 134 +}
 135 +
 136 +static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)
 137 +{
 138 +       unsigned int status;
 139 +
 140 +       /* clear RX_VALID interrupt */
 141 +       ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);
 142 +
 143 +       /* remove characters from the RX FIFO */
 144 +       do {
 145 +               ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);
 146 +               status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
 147 +       } while (status & AR933X_UART_DATA_RX_CSR);
 148 +}
 149 +
 150  static void ar933x_uart_stop_tx(struct uart_port *port)
 151  {
 152         struct ar933x_uart_port *up =
 153 @@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct u
 154         struct ar933x_uart_port *up =
 155                 container_of(port, struct ar933x_uart_port, port);
 156
 157 -       up->ier &= ~AR933X_UART_INT_RX_VALID;
 158 -       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
 159 +       ar933x_uart_stop_rx_interrupt(up);
 160  }
 161
 162  static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
 163 @@ -340,11 +397,20 @@ static void ar933x_uart_rx_chars(struct
 164  static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
 165  {
 166         struct circ_buf *xmit = &up->port.state->xmit;
 167 +       struct serial_rs485 *rs485conf = &up->port.rs485;
 168         int count;
 169 +       bool half_duplex_send = false;
 170
 171         if (uart_tx_stopped(&up->port))
 172                 return;
 173
 174 +       if ((rs485conf->flags & SER_RS485_ENABLED) &&
 175 +           (up->port.x_char || !uart_circ_empty(xmit))) {
 176 +               ar933x_uart_stop_rx_interrupt(up);
 177 +               gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));
 178 +               half_duplex_send = true;
 179 +       }
 180 +
 181         count = up->port.fifosize;
 182         do {
 183                 unsigned int rdata;
 184 @@ -372,8 +438,14 @@ static void ar933x_uart_tx_chars(struct
 185         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 186                 uart_write_wakeup(&up->port);
 187
 188 -       if (!uart_circ_empty(xmit))
 189 +       if (!uart_circ_empty(xmit)) {
 190                 ar933x_uart_start_tx_interrupt(up);
 191 +       } else if (half_duplex_send) {
 192 +               ar933x_uart_wait_tx_complete(up);
 193 +               ar933x_uart_rx_flush(up);
 194 +               ar933x_uart_start_rx_interrupt(up);
 195 +               gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));
 196 +       }
 197  }
 198
 199  static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
 200 @@ -435,8 +507,7 @@ static int ar933x_uart_startup(struct ua
 201                 AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);
 202
 203         /* Enable RX interrupts */
 204 -       up->ier = AR933X_UART_INT_RX_VALID;
 205 -       ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
 206 +       ar933x_uart_start_rx_interrupt(up);
 207
 208         spin_unlock_irqrestore(&up->port.lock, flags);
 209
 210 @@ -519,6 +590,21 @@ static const struct uart_ops ar933x_uart
 211         .verify_port    = ar933x_uart_verify_port,
 212  };
 213
 214 +static int ar933x_config_rs485(struct uart_port *port,
 215 +                               struct serial_rs485 *rs485conf)
 216 +{
 217 +       struct ar933x_uart_port *up =
 218 +               container_of(port, struct ar933x_uart_port, port);
 219 +
 220 +       if ((rs485conf->flags & SER_RS485_ENABLED) &&
 221 +           !up->rts_gpiod) {
 222 +               dev_err(port->dev, "RS485 needs rts-gpio\n");
 223 +               return 1;
 224 +       }
 225 +       port->rs485 = *rs485conf;
 226 +       return 0;
 227 +}
 228 +
 229  #ifdef CONFIG_SERIAL_AR933X_CONSOLE
 230  static struct ar933x_uart_port *
 231  ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
 232 @@ -688,6 +774,8 @@ static int ar933x_uart_probe(struct plat
 233                 goto err_disable_clk;
 234         }
 235
 236 +       uart_get_rs485_mode(&pdev->dev, &port->rs485);
 237 +
 238         port->mapbase = mem_res->start;
 239         port->line = id;
 240         port->irq = irq_res->start;
 241 @@ -698,6 +786,7 @@ static int ar933x_uart_probe(struct plat
 242         port->regshift = 2;
 243         port->fifosize = AR933X_UART_FIFO_SIZE;
 244         port->ops = &ar933x_uart_ops;
 245 +       port->rs485_config = ar933x_config_rs485;
 246
 247         baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
 248         up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
 249 @@ -705,6 +794,18 @@ static int ar933x_uart_probe(struct plat
 250         baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
 251         up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
 252
 253 +       up->gpios = mctrl_gpio_init(port, 0);
 254 +       if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
 255 +               return PTR_ERR(up->gpios);
 256 +
 257 +       up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);
 258 +
 259 +       if ((port->rs485.flags & SER_RS485_ENABLED) &&
 260 +           !up->rts_gpiod) {
 261 +               dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
 262 +               port->rs485.flags &= ~SER_RS485_ENABLED;
 263 +       }
 264 +
 265  #ifdef CONFIG_SERIAL_AR933X_CONSOLE
 266         ar933x_console_ports[up->port.line] = up;
 267  #endif