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authorLinus Walleij <linus.walleij@linaro.org>2019-07-02 21:39:59 +0200
committerLinus Walleij <linus.walleij@linaro.org>2019-07-02 22:31:37 +0200
commitfbbf145a0e0a0177e089c52275fbfa55763e7d1d (patch)
tree9677741c28c810e5680f7664f67aabb430b05e61
parent4b972a01a7da614b4796475f933094751a295a2f (diff)
gpio/spi: Fix spi-gpio regression on active high CSgpio-v5.2-4
I ran into an intriguing bug caused by commit ""spi: gpio: Don't request CS GPIO in DT use-case" affecting all SPI GPIO devices with an active high chip select line. The commit switches the CS gpio handling over to the GPIO core, which will parse and handle "cs-gpios" from the OF node without even calling down to the driver to get the job done. However the GPIO core handles the standard bindings in Documentation/devicetree/bindings/spi/spi-controller.yaml that specifies that active high CS needs to be specified using "spi-cs-high" in the DT node. The code in drivers/spi/spi-gpio.c never respected this and never tried to inspect subnodes to see if they contained "spi-cs-high" like the gpiolib OF quirks does. Instead the only way to get an active high CS was to tag it in the device tree using the flags cell such as cs-gpios = <&gpio 4 GPIO_ACTIVE_HIGH>; This alters the quirks to not inspect the subnodes of SPI masters on "spi-gpio" for the standard attribute "spi-cs-high", making old device trees work as expected. This semantic is a bit ambigous, but just allowing the flags on the GPIO descriptor to modify polarity is what the kernel at large mostly uses so let's encourage that. Fixes: 249e2632dcd0 ("spi: gpio: Don't request CS GPIO in DT use-case") Cc: Andrey Smirnov <andrew.smirnov@gmail.com> Cc: linux-gpio@vger.kernel.org Cc: linux-spi@vger.kernel.org Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
-rw-r--r--drivers/gpio/gpiolib-of.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index aec7bd86ae7e..9c9b965d7d6d 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -118,8 +118,15 @@ static void of_gpio_flags_quirks(struct device_node *np,
* Legacy handling of SPI active high chip select. If we have a
* property named "cs-gpios" we need to inspect the child node
* to determine if the flags should have inverted semantics.
+ *
+ * This does not apply to an SPI device named "spi-gpio", because
+ * these have traditionally obtained their own GPIOs by parsing
+ * the device tree directly and did not respect any "spi-cs-high"
+ * property on the SPI bus children.
*/
- if (IS_ENABLED(CONFIG_SPI_MASTER) && !strcmp(propname, "cs-gpios") &&
+ if (IS_ENABLED(CONFIG_SPI_MASTER) &&
+ !strcmp(propname, "cs-gpios") &&
+ !of_device_is_compatible(np, "spi-gpio") &&
of_property_read_bool(np, "cs-gpios")) {
struct device_node *child;
u32 cs;

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