Re: [PATCH v2 1/3] drm/i915: Skip register reads in i915_get_crtc_scanoutpos()

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Sep 23, 2013 at 02:48:50PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> We have all the information we need in the mode structure, so going and
> reading it from the hardware is pointless, and slower.
> 
> We never populated ->get_vblank_timestamp() in the UMS case, and as that
> is the only way we'd ever call ->get_scanout_position(), we can
> completely ignore UMS in i915_get_crtc_scanoutpos().
> 
> Also reorganize intel_irq_init() a bit to clarify the KMS vs. UMS
> situation.
> 
> v2: Drop UMS code
> 
> Cc: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_irq.c | 43 ++++++++++++++++-------------------------
>  1 file changed, 17 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index b356dc1..058f099 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -570,24 +570,29 @@ static u32 gm45_get_vblank_counter(struct drm_device *dev, int pipe)
>  static int i915_get_crtc_scanoutpos(struct drm_device *dev, int pipe,
>  			     int *vpos, int *hpos)
>  {
> -	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
> -	u32 vbl = 0, position = 0;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> +	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> +	const struct drm_display_mode *mode = &intel_crtc->config.adjusted_mode;
> +	u32 position;
>  	int vbl_start, vbl_end, htotal, vtotal;
>  	bool in_vbl = true;
>  	int ret = 0;
> -	enum transcoder cpu_transcoder = intel_pipe_to_cpu_transcoder(dev_priv,
> -								      pipe);

Hooray, this rips out the racy pipe_to_cpu_transcoder deref, so I'm all in
favour \o/ Of course I still have that ugly itme on my todo about "fix the
locking for kms vblank stuff" ;-)

Mario, can you please take a look at these patches and ack them? I'd like
to slurp them in for -next.
-Daniel

>  
> -	if (!i915_pipe_enabled(dev, pipe)) {
> +	if (!intel_crtc->active) {
>  		DRM_DEBUG_DRIVER("trying to get scanoutpos for disabled "
>  				 "pipe %c\n", pipe_name(pipe));
>  		return 0;
>  	}
>  
> -	/* Get vtotal. */
> -	vtotal = 1 + ((I915_READ(VTOTAL(cpu_transcoder)) >> 16) & 0x1fff);
> +	htotal = mode->crtc_htotal;
> +	vtotal = mode->crtc_vtotal;
> +	vbl_start = mode->crtc_vblank_start;
> +	vbl_end = mode->crtc_vblank_end;
>  
> -	if (INTEL_INFO(dev)->gen >= 4) {
> +	ret |= DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_ACCURATE;
> +
> +	if (IS_G4X(dev) || INTEL_INFO(dev)->gen >= 5) {
>  		/* No obvious pixelcount register. Only query vertical
>  		 * scanout position from Display scan line register.
>  		 */
> @@ -605,29 +610,16 @@ static int i915_get_crtc_scanoutpos(struct drm_device *dev, int pipe,
>  		 */
>  		position = (I915_READ(PIPEFRAMEPIXEL(pipe)) & PIPE_PIXEL_MASK) >> PIPE_PIXEL_SHIFT;
>  
> -		htotal = 1 + ((I915_READ(HTOTAL(cpu_transcoder)) >> 16) & 0x1fff);
>  		*vpos = position / htotal;
>  		*hpos = position - (*vpos * htotal);
>  	}
>  
> -	/* Query vblank area. */
> -	vbl = I915_READ(VBLANK(cpu_transcoder));
> -
> -	/* Test position against vblank region. */
> -	vbl_start = vbl & 0x1fff;
> -	vbl_end = (vbl >> 16) & 0x1fff;
> -
> -	if ((*vpos < vbl_start) || (*vpos > vbl_end))
> -		in_vbl = false;
> +	in_vbl = *vpos >= vbl_start && *vpos < vbl_end;
>  
>  	/* Inside "upper part" of vblank area? Apply corrective offset: */
>  	if (in_vbl && (*vpos >= vbl_start))
>  		*vpos = *vpos - vtotal;
>  
> -	/* Readouts valid? */
> -	if (vbl > 0)
> -		ret |= DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_ACCURATE;
> -
>  	/* In vblank? */
>  	if (in_vbl)
>  		ret |= DRM_SCANOUTPOS_INVBL;
> @@ -3148,11 +3140,10 @@ void intel_irq_init(struct drm_device *dev)
>  		dev->driver->get_vblank_counter = gm45_get_vblank_counter;
>  	}
>  
> -	if (drm_core_check_feature(dev, DRIVER_MODESET))
> +	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
>  		dev->driver->get_vblank_timestamp = i915_get_vblank_timestamp;
> -	else
> -		dev->driver->get_vblank_timestamp = NULL;
> -	dev->driver->get_scanout_position = i915_get_crtc_scanoutpos;
> +		dev->driver->get_scanout_position = i915_get_crtc_scanoutpos;
> +	}
>  
>  	if (IS_VALLEYVIEW(dev)) {
>  		dev->driver->irq_handler = valleyview_irq_handler;
> -- 
> 1.8.1.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch