From 2cbd27267ffe020af1442b95ec57f59a157ba85c Mon Sep 17 00:00:00 2001
From: Kamal Dasu <kdasu.kdev@gmail.com>
Date: Thu, 27 Jan 2022 13:53:59 -0500
Subject: [PATCH] spi: bcm-qspi: check for valid cs before applying chip select
Git-commit: 2cbd27267ffe020af1442b95ec57f59a157ba85c
Patch-mainline: v5.17-rc3
References: git-fixes

Apply only valid chip select value. This change fixes case where chip
select is set to initial value of '-1' during probe and  PM supend and
subsequent resume can try to use the value with undefined behaviour.
Also in case where gpio based chip select, the check in
bcm_qspi_chip_select() shall prevent undefined behaviour on resume.

Fixes: fa236a7ef240 ("spi: bcm-qspi: Add Broadcom MSPI driver")
Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220127185359.27322-1-kdasu.kdev@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/spi/spi-bcm-qspi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c
index c9a769b8594b..86c76211b3d3 100644
--- a/drivers/spi/spi-bcm-qspi.c
+++ b/drivers/spi/spi-bcm-qspi.c
@@ -585,7 +585,7 @@ static void bcm_qspi_chip_select(struct bcm_qspi *qspi, int cs)
 	u32 rd = 0;
 	u32 wr = 0;
 
-	if (qspi->base[CHIP_SELECT]) {
+	if (cs >= 0 && qspi->base[CHIP_SELECT]) {
 		rd = bcm_qspi_read(qspi, CHIP_SELECT, 0);
 		wr = (rd & ~0xff) | (1 << cs);
 		if (rd == wr)
-- 
2.31.1