Re: [PATCH 2/2] drm/i915/tv: Use the scanline counter for timestamps on i965gm TV output

[Imre Deak <imre.deak@intel.com>]

On Fri, Jan 25, 2019 at 08:19:31PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Just like the frame counter, the pixel counter also reads zero
> all the time when the TV encoder is used. Fortunately the
> scanline counter still works sufficiently well so let's use that
> to correct the vblank timestamps. Otherwise the timestamps may
> en up out of whack, and since we use them to guesstimate the
> vblank counter value that may end up incorrect as well.
> 
> Cc: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/i915_irq.c  |  7 +++++--
>  drivers/gpu/drm/i915/intel_drv.h |  4 +++-
>  drivers/gpu/drm/i915/intel_tv.c  | 10 ++++++++++
>  3 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index fe097725c27a..caade521c174 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1014,6 +1014,9 @@ static bool i915_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
>  	int position;
>  	int vbl_start, vbl_end, hsync_start, htotal, vtotal;
>  	unsigned long irqflags;
> +	bool use_scanline_counter = INTEL_GEN(dev_priv) >= 5 ||
> +		IS_G4X(dev_priv) || IS_GEN(dev_priv, 2) ||
> +		mode->private_flags & I915_MODE_FLAG_USE_SCANLINE_COUNTER;
>  
>  	if (WARN_ON(!mode->crtc_clock)) {
>  		DRM_DEBUG_DRIVER("trying to get scanoutpos for disabled "
> @@ -1046,7 +1049,7 @@ static bool i915_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
>  	if (stime)
>  		*stime = ktime_get();
>  
> -	if (IS_GEN(dev_priv, 2) || IS_G4X(dev_priv) || INTEL_GEN(dev_priv) >= 5) {
> +	if (use_scanline_counter) {
>  		/* No obvious pixelcount register. Only query vertical
>  		 * scanout position from Display scan line register.
>  		 */
> @@ -1106,7 +1109,7 @@ static bool i915_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
>  	else
>  		position += vtotal - vbl_end;
>  
> -	if (IS_GEN(dev_priv, 2) || IS_G4X(dev_priv) || INTEL_GEN(dev_priv) >= 5) {
> +	if (use_scanline_counter) {
>  		*vpos = position;
>  		*hpos = 0;
>  	} else {
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 85b913ea6e80..90ba5436370e 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -630,9 +630,11 @@ struct intel_crtc_scaler_state {
>  };
>  
>  /* drm_mode->private_flags */
> -#define I915_MODE_FLAG_INHERITED 1
> +#define I915_MODE_FLAG_INHERITED (1<<0)
>  /* Flag to get scanline using frame time stamps */
>  #define I915_MODE_FLAG_GET_SCANLINE_FROM_TIMESTAMP (1<<1)
> +/* Flag to use the scanline counter instead of the pixel counter */
> +#define I915_MODE_FLAG_USE_SCANLINE_COUNTER (1<<2)
>  
>  struct intel_pipe_wm {
>  	struct intel_wm_level wm[5];
> diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
> index 78be08e2971b..751b88dde18e 100644
> --- a/drivers/gpu/drm/i915/intel_tv.c
> +++ b/drivers/gpu/drm/i915/intel_tv.c
> @@ -1150,6 +1150,11 @@ intel_tv_get_config(struct intel_encoder *encoder,
>  				 ypos, mode.vdisplay - ysize - ypos);
>  
>  	adjusted_mode->crtc_clock = mode.clock;
> +
> +	/* pixel counter doesn't work on i965gm TV output */
> +	if (IS_I965GM(dev_priv))
> +		adjusted_mode->private_flags |=
> +			I915_MODE_FLAG_USE_SCANLINE_COUNTER;
>  }
>  
>  static int
> @@ -1295,6 +1300,11 @@ intel_tv_compute_config(struct intel_encoder *encoder,
>  	drm_mode_set_crtcinfo(adjusted_mode, 0);
>  	adjusted_mode->name[0] = '\0';
>  
> +	/* pixel counter doesn't work on i965gm TV output */
> +	if (IS_I965GM(dev_priv))
> +		adjusted_mode->private_flags |=
> +			I915_MODE_FLAG_USE_SCANLINE_COUNTER;
> +
>  	return 0;
>  }
>  
> -- 
> 2.19.2
> 
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