linux-kernel - [PATCH 4.9 38/48] spi: bcm-qspi: check for valid cs before applying chip select

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Date:   Mon,  7 Feb 2022 12:06:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kamal Dasu <kdasu.kdev@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 4.9 38/48] spi: bcm-qspi: check for valid cs before applying chip select

From: Kamal Dasu <kdasu.kdev@...il.com>

commit 2cbd27267ffe020af1442b95ec57f59a157ba85c upstream.

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@...il.com>
Acked-by: Florian Fainelli <f.fainelli@...il.com>
Link: https://lore.kernel.org/r/20220127185359.27322-1-kdasu.kdev@gmail.com
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/spi/spi-bcm-qspi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/spi/spi-bcm-qspi.c
+++ b/drivers/spi/spi-bcm-qspi.c
@@ -546,7 +546,7 @@ static void bcm_qspi_chip_select(struct
 	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)