cs5535-gpio: don't apply errata #36 to edge detect GPIOs

The edge detect status GPIOs function differently from the other atomic
model CS5536 GPIO registers; writing 1 to the high bits clears the GPIO,
but writing 1 to the lower bits also clears the bit.

This means that read-modify-write doesn't actually work for it, so don't
apply the errata here.  If a negative edge status gets lost after
resume..  well, we tried our best!

Tested-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/gpio/cs5535-gpio.c b/drivers/gpio/cs5535-gpio.c
index 599f6c9e0fbf..79eb9c5a2923 100644
--- a/drivers/gpio/cs5535-gpio.c
+++ b/drivers/gpio/cs5535-gpio.c
@@ -56,15 +56,22 @@ static struct cs5535_gpio_chip {
  * registers, see include/linux/cs5535.h.
  */
 
-static void errata_outl(u32 val, unsigned long addr)
+static void errata_outl(struct cs5535_gpio_chip *chip, u32 val,
+                unsigned int reg)
 {
+        unsigned long addr = chip->base + 0x80 + reg;
+
         /*
          * According to the CS5536 errata (#36), after suspend
          * a write to the high bank GPIO register will clear all
          * non-selected bits; the recommended workaround is a
          * read-modify-write operation.
+         *
+         * Don't apply this errata to the edge status GPIOs, as writing
+         * to their lower bits will clear them.
          */
-        val |= inl(addr);
+        if (reg != GPIO_POSITIVE_EDGE_STS && reg != GPIO_NEGATIVE_EDGE_STS)
+                val |= inl(addr);
         outl(val, addr);
 }
 
@@ -76,7 +83,7 @@ static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset,
                 outl(1 << offset, chip->base + reg);
         else
                 /* high bank register */
-                errata_outl(1 << (offset - 16), chip->base + 0x80 + reg);
+                errata_outl(chip, 1 << (offset - 16), reg);
 }
 
 void cs5535_gpio_set(unsigned offset, unsigned int reg)
@@ -98,7 +105,7 @@ static void __cs5535_gpio_clear(struct cs5535_gpio_chip *chip, unsigned offset,
                 outl(1 << (offset + 16), chip->base + reg);
         else
                 /* high bank register */
-                errata_outl(1 << offset, chip->base + 0x80 + reg);
+                errata_outl(chip, 1 << offset, reg);
 }
 
 void cs5535_gpio_clear(unsigned offset, unsigned int reg)