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authorAndres Salomon <dilinger@queued.net>2010-12-02 14:31:17 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-12-02 14:51:15 -0800
commit853ff88324a248a9f5da6e110850223db353ec07 (patch)
tree6e48a44c672123d8671af2bffedfefee68133151 /drivers
parent238af8751f64a75f8b638193353b1c31ea32e738 (diff)
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cs5535-gpio: apply CS5536 errata workaround for GPIOs
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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpio/cs5535-gpio.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/gpio/cs5535-gpio.c b/drivers/gpio/cs5535-gpio.c
index e23c06893d1..599f6c9e0fb 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)