There are two problems with the current vfe_disable_output() routine.
Firstly we rightly use a spinlock to protect output->gen2.active_num
everywhere except for in the IDLE timeout path of vfe_disable_output().
Even if that is not racy "in practice" somehow it is by happenstance not
by design.
Secondly we do not get consistent behaviour from this routine. On
sc8280xp 50% of the time I get "VFE idle timeout - resetting". In this
case the subsequent capture will succeed. The other 50% of the time, we
don't hit the idle timeout, never do the VFE reset and subsequent
captures stall indefinitely.
Rewrite the vfe_disable_output() routine to
- Quiesce write masters with vfe_wm_stop()
- Set active_num = 0
remembering to hold the spinlock when we do so followed by
- Reset the VFE
Testing on sc8280xp and sdm845 shows this to be a valid fix.
Fixes: 7319cdf189 ("media: camss: Add support for VFE hardware version Titan 170")
Cc: stable@vger.kernel.org
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
3143ad282f