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Subject[PATCH AUTOSEL 5.4 012/187] spi: fsl: Handle the single hardwired chipselect case
Date
From: Linus Walleij <linus.walleij@linaro.org>

[ Upstream commit 7251953d784baf7e5416afabe030a0e81de1a938 ]

The Freescale MPC8xxx had a special quirk for handling a
single hardwired chipselect, the case when we're using neither
GPIO nor native chip select: when inspecting the device tree
and finding zero "cs-gpios" on the device node the code would
assume we have a single hardwired chipselect that leaves the
device always selected.

This quirk is not handled by the new core code, so we need
to check the "cs-gpios" explicitly in the driver and set
pdata->max_chipselect = 1 which will later fall through to
the SPI master ->num_chipselect.

Make sure not to assign the chip select handler in this
case: there is no handling needed since the chip is always
selected, and this is what the old code did as well.

Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Fixes: 0f0581b24bd0 ("spi: fsl: Convert to use CS GPIO descriptors")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> (No tested the
Link: https://lore.kernel.org/r/20191128083718.39177-3-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-fsl-spi.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 75b765f97df5..2155294eaaeb 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -729,8 +729,18 @@ static int of_fsl_spi_probe(struct platform_device *ofdev)
}
}
#endif
-
- pdata->cs_control = fsl_spi_cs_control;
+ /*
+ * Handle the case where we have one hardwired (always selected)
+ * device on the first "chipselect". Else we let the core code
+ * handle any GPIOs or native chip selects and assign the
+ * appropriate callback for dealing with the CS lines. This isn't
+ * supported on the GRLIB variant.
+ */
+ ret = gpiod_count(dev, "cs");
+ if (ret <= 0)
+ pdata->max_chipselect = 1;
+ else
+ pdata->cs_control = fsl_spi_cs_control;
}

ret = of_address_to_resource(np, 0, &mem);
--
2.20.1
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