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: 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>

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index c87e9c4506c2fd969a51d755484ed7246bb8a34a..4b70887cf4438a9556f7db180c05feb4ac44512c 100644 (file)
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -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);