FAILED: patch "[PATCH] serial: sc16is7xx: set safe default SPI clock frequency" failed to apply to 4.19-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 3ef79cd1412236d884ab0c46b4d1921380807b48
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024012241-tactile-unison-0225@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

3ef79cd14122 ("serial: sc16is7xx: set safe default SPI clock frequency")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 3ef79cd1412236d884ab0c46b4d1921380807b48 Mon Sep 17 00:00:00 2001
From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Date: Thu, 21 Dec 2023 18:18:10 -0500
Subject: [PATCH] serial: sc16is7xx: set safe default SPI clock frequency

15 MHz is supported only by 76x variants.

If the SPI clock frequency is not specified, use a safe default clock value
of 4 MHz that is supported by all variants.

Also use HZ_PER_MHZ macro to improve readability.

Fixes: 2c837a8a8f9f ("sc16is7xx: spi interface is added")
Cc:  <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20231221231823.2327894-4-hugo@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 798fa115b28a..ced2446909a2 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -24,6 +24,7 @@
 #include <linux/tty_flip.h>
 #include <linux/spi/spi.h>
 #include <linux/uaccess.h>
+#include <linux/units.h>
 #include <uapi/linux/sched/types.h>
 
 #define SC16IS7XX_NAME			"sc16is7xx"
@@ -1738,7 +1739,7 @@ static int sc16is7xx_spi_probe(struct spi_device *spi)
 		return dev_err_probe(&spi->dev, -EINVAL, "Unsupported SPI mode\n");
 
 	spi->mode		= spi->mode ? : SPI_MODE_0;
-	spi->max_speed_hz	= spi->max_speed_hz ? : 15000000;
+	spi->max_speed_hz	= spi->max_speed_hz ? : 4 * HZ_PER_MHZ;
 	ret = spi_setup(spi);
 	if (ret)
 		return ret;