Messages in this thread Patch in this message | | | Date | Mon, 29 Nov 2010 17:19:30 -0800 | From | Andres Salomon <> | Subject | [PATCH] 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> --- drivers/gpio/cs5535-gpio.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/cs5535-gpio.c b/drivers/gpio/cs5535-gpio.c index e23c068..599f6c9 100644 --- a/drivers/gpio/cs5535-gpio.c +++ b/drivers/gpio/cs5535-gpio.c @@ -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) -- 1.5.6.5
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