• Hans de Goede's avatar
    pinctrl: baytrail: Really serialize all register accesses · 40ecab55
    Hans de Goede authored
    Commit 39ce8150 ("pinctrl: baytrail: Serialize all register access")
    added a spinlock around all register accesses because:
    
    "There is a hardware issue in Intel Baytrail where concurrent GPIO register
     access might result reads of 0xffffffff and writes might get dropped
     completely."
    
    Testing has shown that this does not catch all cases, there are still
    2 problems remaining
    
    1) The original fix uses a spinlock per byt_gpio device / struct,
    additional testing has shown that this is not sufficient concurent
    accesses to 2 different GPIO banks also suffer from the same problem.
    
    This commit fixes this by moving to a single global lock.
    
    2) The original fix did not add a lock around the register accesses in
    the suspend/resume handling.
    
    Since pinctrl-baytrail.c is using normal suspend/resume handlers,
    interrupts are still enabled during suspend/resume handling. Nothing
    should be using the GPIOs when they are being taken down, _but_ the
    GPIOs themselves may still cause interrupts, which are likely to
    use (read) the triggering GPIO. So we need to protect against
    concurrent GPIO register accesses in the suspend/resume handlers too.
    
    This commit fixes this by adding the missing spin_lock / unlock calls.
    
    The 2 fixes together fix the Acer Switch 10 SW5-012 getting completely
    confused after a suspend resume. The DSDT for this device has a bug
    in its _LID method which reprograms the home and power button trigger-
    flags requesting both high and low _level_ interrupts so the IRQs for
    these 2 GPIOs continuously fire. This combined with the saving of
    registers during suspend, triggers concurrent GPIO register accesses
    resulting in saving 0xffffffff as pconf0 value during suspend and then
    when restoring this on resume the pinmux settings get all messed up,
    resulting in various I2C busses being stuck, the wifi no longer working
    and often the tablet simply not coming out of suspend at all.
    
    Cc: stable@vger.kernel.org
    Fixes: 39ce8150 ("pinctrl: baytrail: Serialize all register access")
    Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
    Acked-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
    40ecab55
pinctrl-baytrail.c 47.5 KB