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: 7319cdf189bb ("media: camss: Add support for VFE hardware version Titan 170")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
---
.../media/platform/qcom/camss/camss-vfe-170.c | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)
diff --git a/drivers/media/platform/qcom/camss/camss-vfe-170.c b/drivers/media/platform/qcom/camss/camss-vfe-170.c
index 02494c89da91c..ae9137633c301 100644
--- a/drivers/media/platform/qcom/camss/camss-vfe-170.c
+++ b/drivers/media/platform/qcom/camss/camss-vfe-170.c
@@ -500,28 +500,15 @@ static int vfe_disable_output(struct vfe_line *line)
struct vfe_output *output = &line->output;
unsigned long flags;
unsigned int i;
- bool done;
- int timeout = 0;
-
- do {
- spin_lock_irqsave(&vfe->output_lock, flags);
- done = !output->gen2.active_num;
- spin_unlock_irqrestore(&vfe->output_lock, flags);
- usleep_range(10000, 20000);
-
- if (timeout++ == 100) {
- dev_err(vfe->camss->dev, "VFE idle timeout - resetting\n");
- vfe_reset(vfe);
- output->gen2.active_num = 0;
- return 0;
- }
- } while (!done);
spin_lock_irqsave(&vfe->output_lock, flags);
for (i = 0; i < output->wm_num; i++)
vfe_wm_stop(vfe, output->wm_idx[i]);
+ output->gen2.active_num = 0;
spin_unlock_irqrestore(&vfe->output_lock, flags);
+ vfe_reset(vfe);
+
return 0;
}
--
2.41.0
