target/linux/bcm27xx/patches-5.10/950-0277-serial-8250-bcm2835aux-defer-if-clock-is-zero.patch

   1 From e3af8dd4ba4fc1ae6260823dfb3a82236471c353 Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.com>
   3 Date: Thu, 2 Jul 2020 13:53:20 +0100
   4 Subject: [PATCH] serial: 8250: bcm2835aux - defer if clock is zero
   5
   6 See: https://github.com/raspberrypi/linux/issues/3700
   7
   8 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
   9 ---
  10  drivers/tty/serial/8250/8250_bcm2835aux.c | 7 +++++++
  11  1 file changed, 7 insertions(+)
  12
  13 --- a/drivers/tty/serial/8250/8250_bcm2835aux.c
  14 +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
  15 @@ -148,6 +148,13 @@ static int bcm2835aux_serial_probe(struc
  16          */
  17         up.port.uartclk = clk_get_rate(data->clk) * 2;
  18
  19 +       /* The clock is only queried at probe time, which means we get one shot
  20 +        * at this. A zero clock is never going to work and is almost certainly
  21 +        * due to a parent not being ready, so prefer to defer.
  22 +        */
  23 +       if (!up.port.uartclk)
  24 +           return -EPROBE_DEFER;
  25 +
  26         /* register the port */
  27         ret = serial8250_register_8250_port(&up);
  28         if (ret < 0) {