On Thu, 10 Sep 2020, Uma Shankar <[email protected]> wrote:
> Add a vblank wait when fbc activation request comes for the
> same frame on TGL. This helps fix underrun related to fbc.
>
> Signed-off-by: Uma Shankar <[email protected]>
> ---
> drivers/gpu/drm/i915/display/intel_fbc.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c
> b/drivers/gpu/drm/i915/display/intel_fbc.c
> index 135f5e8a4d70..3e1d715e4a4e 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -1055,6 +1055,7 @@ static void __intel_fbc_post_update(struct intel_crtc
> *crtc)
> {
> struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> struct intel_fbc *fbc = &dev_priv->fbc;
> + static u32 old_frame_cnt, new_frame_cnt;
In the strongest terms, do not add static data. These would be shared
across devices, which is certainly a bug.
BR,
Jani.
>
> drm_WARN_ON(&dev_priv->drm, !mutex_is_locked(&fbc->lock));
>
> @@ -1075,10 +1076,18 @@ static void __intel_fbc_post_update(struct intel_crtc
> *crtc)
> if (!intel_fbc_can_activate(crtc))
> return;
>
> - if (!fbc->busy_bits)
> + old_frame_cnt = new_frame_cnt;
> + new_frame_cnt = intel_crtc_get_vblank_counter(crtc);
> + if (!fbc->busy_bits) {
> + if (IS_TIGERLAKE(dev_priv) &&
> + old_frame_cnt == new_frame_cnt) {
> + drm_dbg_kms(&dev_priv->drm, "Wait for vblank before
> Activating FBC");
> + intel_wait_for_vblank_if_active(dev_priv, crtc->pipe);
> + }
> intel_fbc_hw_activate(dev_priv);
> - else
> + } else {
> intel_fbc_deactivate(dev_priv, "frontbuffer write");
> + }
> }
>
> void intel_fbc_post_update(struct intel_atomic_state *state,
--
Jani Nikula, Intel Open Source Graphics Center
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