spi: rockchip: Fix error in SPI slave pio read

Jon Lin · broonie · commit 4294e4accf8d · 2020-07-28T17:29:31.000+01:00
The RXFLR is possible larger than rx_left in Rockchip SPI, fix it. Fixes: 01b59ce ("spi: rockchip: use irq rather than polling") Signed-off-by: Jon Lin <jon.lin@rock-chips.com> Tested-by: Emil Renner Berthing <kernel@esmil.dk> Reviewed-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Emil Renner Berthing <kernel@esmil.dk> Link: https://lore.kernel.org/r/20200723004356.6390-3-jon.lin@rock-chips.com Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
@@ -291,7 +291,7 @@ static void rockchip_spi_pio_writer(struct rockchip_spi *rs)
 static void rockchip_spi_pio_reader(struct rockchip_spi *rs)
 {
 	u32 words = readl_relaxed(rs->regs + ROCKCHIP_SPI_RXFLR);
-	u32 rx_left = rs->rx_left - words;
+	u32 rx_left = (rs->rx_left > words) ? rs->rx_left - words : 0;
 
 	/* the hardware doesn't allow us to change fifo threshold
 	 * level while spi is enabled, so instead make sure to leave

Original file line number	Diff line number	Diff line change
`@@ -291,7 +291,7 @@ static void rockchip_spi_pio_writer(struct rockchip_spi *rs)`
`291`	`291`	`static void rockchip_spi_pio_reader(struct rockchip_spi *rs)`
`292`	`292`	`{`
`293`	`293`	`u32 words = readl_relaxed(rs->regs + ROCKCHIP_SPI_RXFLR);`
`294`		`- u32 rx_left = rs->rx_left - words;`
	`294`	`+ u32 rx_left = (rs->rx_left > words) ? rs->rx_left - words : 0;`
`295`	`295`
`296`	`296`	`/* the hardware doesn't allow us to change fifo threshold`
`297`	`297`	`* level while spi is enabled, so instead make sure to leave`