Re: [Intel-gfx] [V13 5/5] drm/i915/dsi: Enable software vblank counter

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Sep 22, 2020 at 07:14:26PM +0530, Vandita Kulkarni wrote:
> In case of DSI cmd mode, we get hw vblank counter
> updated after the TE comes in, if we try to read
> the hw vblank counter in te handler we wouldnt have
> the udpated vblank counter yet.
> This will lead to a state where we would send the
> vblank event to the user space in the next te,
> though the frame update would have completed in
> the first TE duration itself.
> Hence switch to using software timestamp based
> vblank counter.
> 
> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 11 +++++++++++
>  drivers/gpu/drm/i915/i915_irq.c              |  4 ++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index c4f331f2af45..8b9e59e52708 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -1808,6 +1808,17 @@ enum pipe intel_crtc_pch_transcoder(struct intel_crtc *crtc)
>  static u32 intel_crtc_max_vblank_count(const struct intel_crtc_state *crtc_state)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc_state->uapi.crtc->dev);
> +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> +	u32 flags = crtc->mode_flags;

That's wrong. You need to look at the crtc_state instead.

> +
> +	/*
> +	 * From Gen 11, In case of dsi cmd mode, frame counter wouldnt
> +	 * have updated at the beginning of TE, if we want to use
> +	 * the hw counter, then we would find it updated in only
> +	 * the next TE, hence switching to sw counter.
> +	 */
> +	if (flags & (I915_MODE_FLAG_DSI_USE_TE0 | I915_MODE_FLAG_DSI_USE_TE1))
> +		return 0;
>  
>  	/*
>  	 * On i965gm the hardware frame counter reads
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index c2e4b227bdf3..634c60befe7e 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -682,8 +682,12 @@ u32 i915_get_vblank_counter(struct drm_crtc *crtc)
>  u32 g4x_get_vblank_counter(struct drm_crtc *crtc)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> +	struct drm_vblank_crtc *vblank = &dev_priv->drm.vblank[drm_crtc_index(crtc)];
>  	enum pipe pipe = to_intel_crtc(crtc)->pipe;
>  
> +	if (!vblank->max_vblank_count)
> +		return 0;
> +
>  	return I915_READ(PIPE_FRMCOUNT_G4X(pipe));
>  }
>  
> -- 
> 2.21.0.5.gaeb582a

-- 
Ville Syrjälä
Intel
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