From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Mark Brown <broonie@kernel.org>
Cc: <linux-spi@vger.kernel.org>,
Tudor Ambarus <Tudor.Ambarus@microchip.com>,
linux-kernel@vger.kernel.org, zhengxunli@mxic.com.tw,
juliensu@mxic.com.tw, ycllin@mxic.com.tw,
Miquel Raynal <miquel.raynal@bootlin.com>
Subject: [PATCH] spi: Fix the logic around the maximum speed
Date: Wed, 3 Feb 2021 18:02:45 +0100 [thread overview]
Message-ID: <20210203170245.31236-1-miquel.raynal@bootlin.com> (raw)
Commit 9326e4f1e5dd ("spi: Limit the spi device max speed to controller's max speed")
rationaly introduced a new condition on which the device's maximum
speed would be set to the controller's one: if the device advertizes a
higher speed than the one supported by the controller.
However, it seems that the SPI core does not enforce controllers to
always advertize a maximum speed value. Other similar conditions in
the SPI core always check that the controller->max_speed_hz was set
before doing anything else.
Not doing this check here breaks SPI controller drivers which do not
advertize a maximum speed:
- the controller maximum speed is 0
- the child device max speed is set to an apparently coeherent value
- in this case the child device maximum speed is set to 0
Either (1) all controller drivers should set max_speed_hz or (2) the
child device maximum speed should not be updated in this particular
situation. Perhaps there is a rationale for not enforcing (1), but in
any case as a fix it is safer to use solution (2).
Fixes: 9326e4f1e5dd ("spi: Limit the spi device max speed to controller's max speed")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.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);
--
2.20.1
next reply other threads:[~2021-02-03 17:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 17:02 Miquel Raynal [this message]
2021-02-03 17:10 ` [PATCH] spi: Fix the logic around the maximum speed Fabio Estevam
2021-02-03 17:14 ` Miquel Raynal
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