Hi Bryan,
Thank you for the patch.
On Tue, Aug 22, 2023 at 09:06:21PM +0100, Bryan O'Donoghue wrote:
> 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>
I can't comment on the validity of the fix, but nothing shocks me in the
patch, so I'm fine with it.
> ---
> .../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);
Now that you don't sleep anymore, I think you can drop the inclusion of
linux/delay.h.
> -
> - 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;
This function could become void, especially given that its only caller
doesn't check the return value.
> }
>
> --
> 2.41.0
>
--
Regards,
Laurent Pinchart
