[PATCH 4.14-4.17 1/2] earlycon: Initialize port->uartclk based on clock-frequency property

["Rafał Miłecki" <zajec5@gmail.com>]

From: Michal Simek <michal.simek@xilinx.com>

commit 814453adea7d081ad8917aa0f32d6a14165a3563 upstream.

On DT based platforms when current-speed property is present baudrate
is setup. Also port->uartclk is initialized to bogus BASE_BAUD * 16
value. Drivers like uartps/ns16550 contain logic when baudrate and
uartclk is used for baudrate calculation.

The patch is reading optional clock-frequency property to replace bogus
BASE_BAUD * 16 calculation to have proper baudrate calculation.

[-stable comment: commit 31cb9a8575ca ("earlycon: initialise baud field
 of earlycon device structure") has changed 8250_early.c behavior which
 now tries to setup UART speed. Ignoring clock-frequency results in
 wrong value of calculated divisor & malformed early console output.]

Fixes: 31cb9a8575ca ("earlycon: initialise baud field of earlycon device structure")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[rmilecki: add -stable comment and Fixes tag]
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
 drivers/tty/serial/earlycon.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index ac667b47f199..05ba1875bb3e 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -289,6 +289,10 @@ int __init of_setup_earlycon(const struct earlycon_id *match,
 	if (val)
 		early_console_dev.baud = be32_to_cpu(*val);
 
+	val = of_get_flat_dt_prop(node, "clock-frequency", NULL);
+	if (val)
+		port->uartclk = be32_to_cpu(*val);
+
 	if (options) {
 		early_console_dev.baud = simple_strtoul(options, NULL, 0);
 		strlcpy(early_console_dev.options, options,
-- 
2.13.7