releases/2.6.36.2/cs5535-gpio-apply-cs5536-errata-workaround-for-gpios.patch

   1 From 853ff88324a248a9f5da6e110850223db353ec07 Mon Sep 17 00:00:00 2001
   2 From: Andres Salomon <dilinger@queued.net>
   3 Date: Thu, 2 Dec 2010 14:31:17 -0800
   4 Subject: cs5535-gpio: apply CS5536 errata workaround for GPIOs
   5
   6 From: Andres Salomon <dilinger@queued.net>
   7
   8 commit 853ff88324a248a9f5da6e110850223db353ec07 upstream.
   9
  10 The AMD Geode CS5536 Companion Device Silicon Revision B1 Specification
  11 Update mentions the follow as issue #36:
  12
  13  "Atomic write transactions to the atomic GPIO High Bank Feature Bit
  14   registers should only affect the bits selected [...]"
  15
  16  "after Suspend, an atomic write transaction [...] will clear all
  17   non-selected bits of the accessed register."
  18
  19 In other words, writing to the high bank for a single GPIO bit will
  20 clear every other GPIO bit (but only sometimes after a suspend).
  21
  22 The workaround described is obvious and simple; do a read-modify-write.
  23 This patch does that, and documents why we're doing it.
  24
  25 Signed-off-by: Andres Salomon <dilinger@queued.net>
  26 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  27 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  29
  30 ---
  31  drivers/gpio/cs5535-gpio.c |   16 ++++++++++++++--
  32  1 file changed, 14 insertions(+), 2 deletions(-)
  33
  34 --- a/drivers/gpio/cs5535-gpio.c
  35 +++ b/drivers/gpio/cs5535-gpio.c
  36 @@ -56,6 +56,18 @@ static struct cs5535_gpio_chip {
  37   * registers, see include/linux/cs5535.h.
  38   */
  39
  40 +static void errata_outl(u32 val, unsigned long addr)
  41 +{
  42 +       /*
  43 +        * According to the CS5536 errata (#36), after suspend
  44 +        * a write to the high bank GPIO register will clear all
  45 +        * non-selected bits; the recommended workaround is a
  46 +        * read-modify-write operation.
  47 +        */
  48 +       val |= inl(addr);
  49 +       outl(val, addr);
  50 +}
  51 +
  52  static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset,
  53                 unsigned int reg)
  54  {
  55 @@ -64,7 +76,7 @@ static void __cs5535_gpio_set(struct cs5
  56                 outl(1 << offset, chip->base + reg);
  57         else
  58                 /* high bank register */
  59 -               outl(1 << (offset - 16), chip->base + 0x80 + reg);
  60 +               errata_outl(1 << (offset - 16), chip->base + 0x80 + reg);
  61  }
  62
  63  void cs5535_gpio_set(unsigned offset, unsigned int reg)
  64 @@ -86,7 +98,7 @@ static void __cs5535_gpio_clear(struct c
  65                 outl(1 << (offset + 16), chip->base + reg);
  66         else
  67                 /* high bank register */
  68 -               outl(1 << offset, chip->base + 0x80 + reg);
  69 +               errata_outl(1 << offset, chip->base + 0x80 + reg);
  70  }
  71
  72  void cs5535_gpio_clear(unsigned offset, unsigned int reg)