spi: fsl: Handle the single hardwired chipselect case

Message ID 20191127084640.105054-1-linus.walleij@linaro.org
State Superseded
Headers show
  • spi: fsl: Handle the single hardwired chipselect case
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Commit Message

Linus Walleij Nov. 27, 2019, 8:46 a.m.
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>

 drivers/spi/spi-fsl-spi.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)



diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 114801a32371..f2188192bf76 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -727,8 +727,17 @@  static int of_fsl_spi_probe(struct platform_device *ofdev)
-		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.
+		 */
+		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);