[PATCH 4/9] serial: 8250: add support for rs485 RTS delays in microseconds

[Martin Kepplinger]

Read struct serial_rs485's flag SER_RS485_DELAY_IN_USEC and apply the delay
accordingly.

Signed-off-by: Martin Kepplinger <martin.kepplin...@ginzinger.com>
---
 drivers/tty/serial/8250/8250_omap.c | 13 +++++++++++--
 drivers/tty/serial/8250/8250_port.c | 25 +++++++++++++++++++++----
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c 
b/drivers/tty/serial/8250/8250_omap.c
index 0a8316632d75..cbce43ac60b1 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -720,8 +720,17 @@ static int omap_8250_rs485_config(struct uart_port *port,
        struct uart_8250_port *up = up_to_u8250p(port);
 
        /* Clamp the delays to [0, 100ms] */
-       rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
-       rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send, 100U);
+       if (rs485->flags & SER_RS485_DELAY_IN_USEC) {
+               rs485->delay_rts_before_send = min(rs485->delay_rts_before_send,
+                                                  100000U);
+               rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send,
+                                                  100000U);
+       } else {
+               rs485->delay_rts_before_send = min(rs485->delay_rts_before_send,
+                                                  100U);
+               rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send,
+                                                  100U);
+       }
 
        port->rs485 = *rs485;
 
diff --git a/drivers/tty/serial/8250/8250_port.c 
b/drivers/tty/serial/8250/8250_port.c
index d2f3310abe54..0cee4aa8323d 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1483,6 +1483,15 @@ static void start_hrtimer_ms(struct hrtimer *hrt, 
unsigned long msec)
        hrtimer_start(hrt, t, HRTIMER_MODE_REL);
 }
 
+static void start_hrtimer_us(struct hrtimer *hrt, unsigned long usec)
+{
+       long sec = usec / 1000000;
+       long nsec = (usec % 1000000) * 1000000000;
+       ktime_t t = ktime_set(sec, nsec);
+
+       hrtimer_start(hrt, t, HRTIMER_MODE_REL);
+}
+
 static void __stop_tx_rs485(struct uart_8250_port *p)
 {
        struct uart_8250_em485 *em485 = p->em485;
@@ -1493,8 +1502,12 @@ static void __stop_tx_rs485(struct uart_8250_port *p)
         */
        if (p->port.rs485.delay_rts_after_send > 0) {
                em485->active_timer = &em485->stop_tx_timer;
-               start_hrtimer_ms(&em485->stop_tx_timer,
-                                  p->port.rs485.delay_rts_after_send);
+               if (p->port.rs485.flags & SER_RS485_DELAY_IN_USEC)
+                       start_hrtimer_us(&em485->stop_tx_timer,
+                                        p->port.rs485.delay_rts_after_send);
+               else
+                       start_hrtimer_ms(&em485->stop_tx_timer,
+                                        p->port.rs485.delay_rts_after_send);
        } else {
                __do_stop_tx_rs485(p);
        }
@@ -1600,8 +1613,12 @@ static inline void start_tx_rs485(struct uart_port *port)
 
                if (up->port.rs485.delay_rts_before_send > 0) {
                        em485->active_timer = &em485->start_tx_timer;
-                       start_hrtimer_ms(&em485->start_tx_timer,
-                                        up->port.rs485.delay_rts_before_send);
+                       if (up->port.rs485.flags & SER_RS485_DELAY_IN_USEC)
+                               start_hrtimer_us(&em485->start_tx_timer,
+                                       up->port.rs485.delay_rts_before_send);
+                       else
+                               start_hrtimer_ms(&em485->start_tx_timer,
+                                       up->port.rs485.delay_rts_before_send);
                        return;
                }
        }
-- 
2.20.1

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