linux-kernel - [PATCH] spi: Fix the clamping of spi->max_speed

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Date:   Wed, 16 Dec 2020 11:23:21 +0200
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <broonie@...nel.org>, <geert@...ux-m68k.org>
CC:     <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>
Subject: [PATCH] spi: Fix the clamping of spi->max_speed_hz

If spi->controller->max_speed_hz is zero, a non-zero spi->max_speed_hz
will be overwritten by zero. Make sure spi->controller->max_speed_hz
is not zero when clamping spi->max_speed_hz.

Put the spi->controller->max_speed_hz non-zero check higher in the if,
so that we avoid a superfluous init to zero when both spi->max_speed_hz
and spi->controller->max_speed_hz are zero.

Fixes: 9326e4f1e5dd ("spi: Limit the spi device max speed to controller's max speed")
Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
---
 drivers/spi/spi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51d7c004fbab..f59bf5094adb 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3378,8 +3378,9 @@ int spi_setup(struct spi_device *spi)
 	if (status)
 		return status;
 
-	if (!spi->max_speed_hz ||
-	    spi->max_speed_hz > spi->controller->max_speed_hz)
+	if (spi->controller->max_speed_hz &&
+	    (!spi->max_speed_hz ||
+	     spi->max_speed_hz > spi->controller->max_speed_hz))
 		spi->max_speed_hz = spi->controller->max_speed_hz;
 
 	mutex_lock(&spi->controller->io_mutex);
-- 
2.25.1