[Intel-gfx] [PATCH] drm/i915: disable IPS while getting the sink CRCs

[Rodrigo Vivi]

I didn't face this since I was letting IPS disabled on my tests here
and the platforms that I'm mostly concerned about sink CRC not working
well are the ones that doesn't have IPS.

I'm not sure this is the right way to solve this issue. Maybe we want
to know the sink CRC when IPS is on.
I believe the right approach is to provide a sysfs interface to toggle
ips off so testcase can disabled ips to not get impacted by it when
reading sink CRC. and than, enable it back if it was enabled after
test is concluded.

But anyway, this is a simple solution that we have right now and we
can change it once we have the sysfs interface, so:
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>



On Mon, May 25, 2015 at 2:52 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>
> This commit is the "sink CRC" version of:
>
> commit 8c740dcea254a1472df2c0ac5ac585412a2507ec
> Author: Paulo Zanoni <paulo.r.zanoni at intel.com>
> Date:   Fri Oct 17 18:42:03 2014 -0300
>     drm/i915: disable IPS while getting the pipe CRCs.
>
> For some unknown reason, when IPS gets enabled, the sink CRC changes.
> Since hsw_enable_ips() doesn't really guarantee to enable IPS (it
> depends on package C-states), we can't really predict if IPS is
> enabled or disabled while running our CRC tests, so let's just
> completely disable IPS while sink CRCs are being used.
>
> If we find a way to make IPS not change the pipe CRC result, we may
> want to fix IPS and then revert this patch (and 8c740dcea too). While
> this doesn't happen, let's merge this patch, so the IGT tests relying
> on sink CRCs can work properly.
>
> This was discovered while developing a new IGT test, which will
> probably be called kms_frontbuffer_tracking.
>
> Testcase: igt/kms_frontbuffer_tracking (not on upstream IGT yet)
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 66 ++++++++++++++++++++++++++++-------------
>  1 file changed, 45 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index abd442a..62662de 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4041,46 +4041,70 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>         u8 buf;
>         int test_crc_count;
>         int attempts = 6;
> +       int ret = 0;
>
> -       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf) < 0)
> -               return -EIO;
> +       hsw_disable_ips(intel_crtc);
>
> -       if (!(buf & DP_TEST_CRC_SUPPORTED))
> -               return -ENOTTY;
> +       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
> +
> +       if (!(buf & DP_TEST_CRC_SUPPORTED)) {
> +               ret = -ENOTTY;
> +               goto out;
> +       }
>
> -       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) < 0)
> -               return -EIO;
> +       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
>
>         if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
> -                               buf | DP_TEST_SINK_START) < 0)
> -               return -EIO;
> +                               buf | DP_TEST_SINK_START) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
> +
> +       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
>
> -       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf) < 0)
> -               return -EIO;
>         test_crc_count = buf & DP_TEST_COUNT_MASK;
>
>         do {
>                 if (drm_dp_dpcd_readb(&intel_dp->aux,
> -                                     DP_TEST_SINK_MISC, &buf) < 0)
> -                       return -EIO;
> +                                     DP_TEST_SINK_MISC, &buf) < 0) {
> +                       ret = -EIO;
> +                       goto out;
> +               }
>                 intel_wait_for_vblank(dev, intel_crtc->pipe);
>         } while (--attempts && (buf & DP_TEST_COUNT_MASK) == test_crc_count);
>
>         if (attempts == 0) {
>                 DRM_DEBUG_KMS("Panel is unable to calculate CRC after 6 vblanks\n");
> -               return -ETIMEDOUT;
> +               ret = -ETIMEDOUT;
> +               goto out;
>         }
>
> -       if (drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_CRC_R_CR, crc, 6) < 0)
> -               return -EIO;
> +       if (drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_CRC_R_CR, crc, 6) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
>
> -       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) < 0)
> -               return -EIO;
> +       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
>         if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
> -                              buf & ~DP_TEST_SINK_START) < 0)
> -               return -EIO;
> -
> -       return 0;
> +                              buf & ~DP_TEST_SINK_START) < 0) {
> +               ret = -EIO;
> +               goto out;
> +       }
> +out:
> +       hsw_enable_ips(intel_crtc);
> +       return ret;
>  }
>
>  static bool
> --
> 2.1.4
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx



-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br