[PATCH] spi: Fix the clamping of spi->max_speed_hz

[PATCH] spi: Fix the clamping of spi->max_speed_hz

[Tudor Ambarus]

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@linux-m68k.org>
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.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

Re: [PATCH] spi: Fix the clamping of spi->max_speed_hz

[Geert Uytterhoeven]

On Wed, Dec 16, 2020 at 10:23 AM Tudor Ambarus
<tudor.ambarus@microchip.com> wrote:
> 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@linux-m68k.org>
> Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] spi: Fix the clamping of spi->max_speed_hz

[Mark Brown]

On Wed, 16 Dec 2020 11:23:21 +0200, Tudor Ambarus wrote:
> 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.

Applied to

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

Thanks!

[1/1] spi: Fix the clamping of spi->max_speed_hz
      commit: 6820e812dafb4258bc14692f686eec5bde6fba86

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.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark