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

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.

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

index c9a769b8594b..86c76211b3d3 100644
@@ -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)

2.17.1

Thanks!

Florian

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-linus

Thanks!

[1/1] spi: bcm-qspi: check for valid cs before applying chip select

      commit: 2cbd27267ffe020af1442b95ec57f59a157ba85c

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

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Thanks,
Mark