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