pinctrl: baytrail: Really serialize all register accesses

[ Upstream commit 40ecab55 ]

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: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>