Re: [PATCH] drm/i915: Wait for vblank after enabling the primary plane on BDW

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 26 Jun 2014, Rodrigo Vivi <rodrigo.vivi@gmail.com> wrote:
> I'm sure this might affect Wayne, so, cc'ing him here.
>
> from my point of view this is right so:
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Pushed to -fixes, thanks for the patch and review.

BR,
Jani.


>
>
> On Tue, Jun 24, 2014 at 3:59 AM, <ville.syrjala@linux.intel.com> wrote:
>
>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>
>> BDW signals the flip done interrupt immediately after the DSPSURF write
>> when the plane is disabled. This is true even if we've already armed
>> DSPCNTR to enable the plane at the next vblank. This causes major
>> problems for our page flip code which relies on the flip done interrupts
>> happening at vblank time.
>>
>> So what happens is that we enable the plane, and immediately allow
>> userspace to submit a page flip. If the plane is still in the process
>> of being enabled when the page flip is issued, the flip done gets
>> signalled immediately. Our DSPSURFLIVE check catches this to prevent
>> premature flip completion, but it also means that we don't get a flip
>> done interrupt when the plane actually gets enabled, and so the page
>> flip is never completed.
>>
>> Work around this by re-introducing blocking vblank waits on BDW
>> whenever we enable the primary plane.
>>
>> I removed some of the vblank waits here:
>>  commit 6304cd91e7f05f8802ea6f91287cac09741d9c46
>>  Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>  Date:   Fri Apr 25 13:30:12 2014 +0300
>>
>>     drm/i915: Drop the excessive vblank waits from modeset codepaths
>>
>> To avoid these blocking vblank waits we should start using the vblank
>> interrupt instead of the flip done interrupt to complete page flips.
>> But that's material for another patch.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79354
>> Tested-by: Guo Jinxian <jinxianx.guo@intel.com>
>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_display.c | 9 +++++++++
>>  drivers/gpu/drm/i915/intel_sprite.c  | 8 ++++++++
>>  2 files changed, 17 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_display.c
>> b/drivers/gpu/drm/i915/intel_display.c
>> index 9188fed..f92efc6 100644
>> --- a/drivers/gpu/drm/i915/intel_display.c
>> +++ b/drivers/gpu/drm/i915/intel_display.c
>> @@ -2087,6 +2087,7 @@ void intel_flush_primary_plane(struct
>> drm_i915_private *dev_priv,
>>  static void intel_enable_primary_hw_plane(struct drm_i915_private
>> *dev_priv,
>>                                           enum plane plane, enum pipe pipe)
>>  {
>> +       struct drm_device *dev = dev_priv->dev;
>>         struct intel_crtc *intel_crtc =
>>                 to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
>>         int reg;
>> @@ -2106,6 +2107,14 @@ static void intel_enable_primary_hw_plane(struct
>> drm_i915_private *dev_priv,
>>
>>         I915_WRITE(reg, val | DISPLAY_PLANE_ENABLE);
>>         intel_flush_primary_plane(dev_priv, plane);
>> +
>> +       /*
>> +        * BDW signals flip done immediately if the plane
>> +        * is disabled, even if the plane enable is already
>> +        * armed to occur at the next vblank :(
>> +        */
>> +       if (IS_BROADWELL(dev))
>> +               intel_wait_for_vblank(dev, intel_crtc->pipe);
>>  }
>>
>>  /**
>> diff --git a/drivers/gpu/drm/i915/intel_sprite.c
>> b/drivers/gpu/drm/i915/intel_sprite.c
>> index 1b66ddc..9a17b4e 100644
>> --- a/drivers/gpu/drm/i915/intel_sprite.c
>> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>> @@ -691,6 +691,14 @@ intel_post_enable_primary(struct drm_crtc *crtc)
>>         struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
>>
>>         /*
>> +        * BDW signals flip done immediately if the plane
>> +        * is disabled, even if the plane enable is already
>> +        * armed to occur at the next vblank :(
>> +        */
>> +       if (IS_BROADWELL(dev))
>> +               intel_wait_for_vblank(dev, intel_crtc->pipe);
>> +
>> +       /*
>>          * FIXME IPS should be fine as long as one plane is
>>          * enabled, but in practice it seems to have problems
>>          * when going from primary only to sprite only and vice
>> --
>> 1.8.5.5
>>
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>>
>
>
>
> -- 
> Rodrigo Vivi
> Blog: http://blog.vivi.eng.br
> _______________________________________________
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-- 
Jani Nikula, Intel Open Source Technology Center
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