Re: [PATCH 28/31] drm/i915: Make Sink crc calculation waiting for counter to reset.

[Paulo Zanoni <przanoni@gmail.com>]

2015-11-05 16:50 GMT-02:00 Rodrigo Vivi <rodrigo.vivi@intel.com>:
> According to VESA DP spec TEST_CRC_COUNT (Bits 3:0) at
> TEST_SINK_MISC (00246h) is "Reset to 0 when TEST_SINK bit 0 = 0;
>
> So let's give few vblanks so we are really sure that this counter
> is really zeroed on the next sink_crc read.
>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index c0fa90a..5d810cd 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3806,6 +3806,8 @@ static int intel_dp_sink_crc_stop(struct intel_dp *intel_dp)
>         struct intel_crtc *intel_crtc = to_intel_crtc(dig_port->base.base.crtc);
>         u8 buf;
>         int ret = 0;
> +       int count = 0;
> +       int attempts = 10;
>
>         if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) < 0) {
>                 DRM_DEBUG_KMS("Sink CRC couldn't be stopped properly\n");
> @@ -3820,7 +3822,22 @@ static int intel_dp_sink_crc_stop(struct intel_dp *intel_dp)
>                 goto out;
>         }
>
> -       intel_wait_for_vblank(dev, intel_crtc->pipe);
> +       do {
> +               intel_wait_for_vblank(dev, intel_crtc->pipe);
> +
> +               if (drm_dp_dpcd_readb(&intel_dp->aux,
> +                                     DP_TEST_SINK_MISC, &buf) < 0) {
> +                       ret = -EIO;
> +                       goto out;

This "goto out" will make sink_crc.started remain as true even though
we already sent the DPCD message telling it to stop, and it
acknowledged our message. And it won't even print stuff on dmesg. I
guess I'd probably write something on dmesg and flip started to false.

> +               }
> +               count = buf & DP_TEST_COUNT_MASK;
> +       } while (--attempts && count);
> +
> +       if (attempts == 0) {
> +               DRM_ERROR("TIMEOUT: Sink CRC counter is not zeroed\n");

The other errors are all DRM_DEBUG_KMS. On one hand we can't do
anything about them since they're most likely panel errors so
DRM_ERROR doesn't look good. On the other hand normal users are not
going to ever run this code, and DRM_ERROR may make us - and our
testing robots - notice the possible failures, so maybe DRM_ERROR is
the way to go here. Anyway, we should be consistent regardless of the
decision.

Besides, at intel_dp_sink_crc_start(), we read the last_count, but
it's supposed to be zero. Can't we use a check for this there too?
Maybe just an informative DRM_DEBUG_KMS("this was supposed to be zero
but it's not\n") without really returning.

Everything else looks good.

> +               ret = -ETIMEDOUT;
> +       }
> +
>         intel_dp->sink_crc.started = false;
>   out:
>         intel_ips_enable(intel_crtc);
> --
> 2.4.3
>
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-- 
Paulo Zanoni
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