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cs5535-gpio: apply CS5536 errata workaround for GPIOs

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The AMD Geode CS5536 Companion Device Silicon Revision B1 Specification
Update mentions the follow as issue #36:

 "Atomic write transactions to the atomic GPIO High Bank Feature Bit
  registers should only affect the bits selected [...]"

 "after Suspend, an atomic write transaction [...] will clear all
  non-selected bits of the accessed register."

In other words, writing to the high bank for a single GPIO bit will
clear every other GPIO bit (but only sometimes after a suspend).

The workaround described is obvious and simple; do a read-modify-write.
This patch does that, and documents why we're doing it.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andres Salomon 2010-12-02 14:31:17 -08:00 committed by Linus Torvalds
parent 238af8751f
commit 853ff88324
1 changed files with 14 additions and 2 deletions
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16
drivers/gpio/cs5535-gpio.c
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@ -56,6 +56,18 @@ static struct cs5535_gpio_chip {
* registers, see include/linux/cs5535.h.
*/
static void errata_outl(u32 val, unsigned long addr)
{
/*
* 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.
*/
val |= inl(addr);
outl(val, addr);
}
static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset,
unsigned int reg)
{
@ -64,7 +76,7 @@ static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset,
outl(1 << offset, chip->base + reg);
else
/* high bank register */
outl(1 << (offset - 16), chip->base + 0x80 + reg);
errata_outl(1 << (offset - 16), chip->base + 0x80 + reg);
}
void cs5535_gpio_set(unsigned offset, unsigned int reg)
@ -86,7 +98,7 @@ static void __cs5535_gpio_clear(struct cs5535_gpio_chip *chip, unsigned offset,
outl(1 << (offset + 16), chip->base + reg);
else
/* high bank register */
outl(1 << offset, chip->base + 0x80 + reg);
errata_outl(1 << offset, chip->base + 0x80 + reg);
}
void cs5535_gpio_clear(unsigned offset, unsigned int reg)