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Commit 853ff883 authored by Andres Salomon's avatar Andres Salomon Committed by Linus Torvalds
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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: default avatarAndres Salomon <dilinger@queued.net>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 238af875

drivers/gpio/cs5535-gpio.c

+14 −2
Original line number Diff line number Diff line
@@ -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)