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    Subject[PATCH] [171/223] cs5535-gpio: apply CS5536 errata workaround for GPIOs
    Date
    2.6.35-longterm review patch.  If anyone has any objections, please let me know.

    ------------------
    From: Andres Salomon <dilinger@queued.net>

    commit 853ff88324a248a9f5da6e110850223db353ec07 upstream.

    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>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: Andi Kleen <ak@linux.intel.com>

    ---
    drivers/gpio/cs5535-gpio.c | 16 ++++++++++++++--
    1 file changed, 14 insertions(+), 2 deletions(-)

    Index: linux/drivers/gpio/cs5535-gpio.c
    ===================================================================
    --- linux.orig/drivers/gpio/cs5535-gpio.c
    +++ linux/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 cs5
    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 c
    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)

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