spi: bcm-qspi: check for valid cs before applying chip select

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c
index 151e154..ae8c86b 100644 (file)
--- a/drivers/spi/spi-bcm-qspi.c
+++ b/drivers/spi/spi-bcm-qspi.c
@@ -552,7 +552,7 @@ 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)