serial: sh-sci: Fix support for hardware-assisted RTS/CTS

The existing support for hardware-assisted RTS/CTS is rudimentary and
doesn't work.

Add support for hardware-assisted RTS/CTS hardware flow control for the
(H)SCIF, SCIFA, and SCIFB variants.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index b9d027a..02b240a 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -141,6 +141,8 @@ struct sci_port {
        struct timer_list               rx_timer;
        unsigned int                    rx_timeout;
 #endif
+
+       bool autorts;
 };
 
 #define SCI_NPORTS CONFIG_SERIAL_SH_SCI_NR_UARTS
@@ -1811,6 +1813,46 @@ static unsigned int sci_tx_empty(struct uart_port *port)
        return (status & SCxSR_TEND(port)) && !in_tx_fifo ? TIOCSER_TEMT : 0;
 }
 
+static void sci_set_rts(struct uart_port *port, bool state)
+{
+       if (port->type == PORT_SCIFA || port->type == PORT_SCIFB) {
+               u16 data = serial_port_in(port, SCPDR);
+
+               /* Active low */
+               if (state)
+                       data &= ~SCPDR_RTSD;
+               else
+                       data |= SCPDR_RTSD;
+               serial_port_out(port, SCPDR, data);
+
+               /* RTS# is output */
+               serial_port_out(port, SCPCR,
+                               serial_port_in(port, SCPCR) | SCPCR_RTSC);
+       } else if (sci_getreg(port, SCSPTR)->size) {
+               u16 ctrl = serial_port_in(port, SCSPTR);
+
+               /* Active low */
+               if (state)
+                       ctrl &= ~SCSPTR_RTSDT;
+               else
+                       ctrl |= SCSPTR_RTSDT;
+               serial_port_out(port, SCSPTR, ctrl);
+       }
+}
+
+static bool sci_get_cts(struct uart_port *port)
+{
+       if (port->type == PORT_SCIFA || port->type == PORT_SCIFB) {
+               /* Active low */
+               return !(serial_port_in(port, SCPDR) & SCPDR_CTSD);
+       } else if (sci_getreg(port, SCSPTR)->size) {
+               /* Active low */
+               return !(serial_port_in(port, SCSPTR) & SCSPTR_CTSDT);
+       }
+
+       return true;
+}
+
 /*
  * Modem control is a bit of a mixed bag for SCI(F) ports. Generally
  * CTS/RTS is supported in hardware by at least one port and controlled
@@ -1841,6 +1883,31 @@ static void sci_set_mctrl(struct uart_port *port, unsigned int mctrl)
        }
 
        mctrl_gpio_set(s->gpios, mctrl);
+
+       if (!(s->cfg->capabilities & SCIx_HAVE_RTSCTS))
+               return;
+
+       if (!(mctrl & TIOCM_RTS)) {
+               /* Disable Auto RTS */
+               serial_port_out(port, SCFCR,
+                               serial_port_in(port, SCFCR) & ~SCFCR_MCE);
+
+               /* Clear RTS */
+               sci_set_rts(port, 0);
+       } else if (s->autorts) {
+               if (port->type == PORT_SCIFA || port->type == PORT_SCIFB) {
+                       /* Enable RTS# pin function */
+                       serial_port_out(port, SCPCR,
+                               serial_port_in(port, SCPCR) & ~SCPCR_RTSC);
+               }
+
+               /* Enable Auto RTS */
+               serial_port_out(port, SCFCR,
+                               serial_port_in(port, SCFCR) | SCFCR_MCE);
+       } else {
+               /* Set RTS */
+               sci_set_rts(port, 1);
+       }
 }
 
 static unsigned int sci_get_mctrl(struct uart_port *port)
@@ -1853,10 +1920,14 @@ static unsigned int sci_get_mctrl(struct uart_port *port)
 
        /*
         * CTS/RTS is handled in hardware when supported, while nothing
-        * else is wired up. Keep it simple and simply assert CTS/DSR/CAR.
+        * else is wired up.
         */
-       if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_CTS)))
+       if (s->autorts) {
+               if (sci_get_cts(port))
+                       mctrl |= TIOCM_CTS;
+       } else if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_CTS))) {
                mctrl |= TIOCM_CTS;
+       }
        if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_DSR)))
                mctrl |= TIOCM_DSR;
        if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_DCD)))
@@ -1927,6 +1998,7 @@ static void sci_shutdown(struct uart_port *port)
 
        dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);
 
+       s->autorts = false;
        mctrl_gpio_disable_ms(to_sci_port(port)->gpios);
 
        spin_lock_irqsave(&port->lock, flags);
@@ -2248,15 +2320,18 @@ done:
 
        sci_init_pins(port, termios->c_cflag);
 
+       port->status &= ~UPSTAT_AUTOCTS;
+       s->autorts = false;
        reg = sci_getreg(port, SCFCR);
        if (reg->size) {
                unsigned short ctrl = serial_port_in(port, SCFCR);
 
-               if (s->cfg->capabilities & SCIx_HAVE_RTSCTS) {
-                       if (termios->c_cflag & CRTSCTS)
-                               ctrl |= SCFCR_MCE;
-                       else
-                               ctrl &= ~SCFCR_MCE;
+               if ((port->flags & UPF_HARD_FLOW) &&
+                   (termios->c_cflag & CRTSCTS)) {
+                       /* There is no CTS interrupt to restart the hardware */
+                       port->status |= UPSTAT_AUTOCTS;
+                       /* MCE is enabled when RTS is raised */
+                       s->autorts = true;
                }
 
                /*
@@ -2958,6 +3033,7 @@ static int sci_probe_single(struct platform_device *dev,
                        dev_err(&dev->dev, "Conflicting RTS/CTS config\n");
                        return -EINVAL;
                }
+               sciport->port.flags |= UPF_HARD_FLOW;
        }
 
        ret = uart_add_one_port(&sci_uart_driver, &sciport->port);