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spi: fsl: Handle the single hardwired chipselect case 

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: 0f0581b24b ("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>
alistair/sunxi64-5.5-dsi
Linus Walleij 2019-11-28 09:37:18 +01:00 committed by Mark Brown
parent 71b8f600b0
commit 7251953d78
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GPG Key ID: 24D68B725D5487D0
1 changed files with 12 additions and 2 deletions
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14
drivers/spi/spi-fsl-spi.c
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@ -728,8 +728,18 @@ 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);