Re: [PATCH v2 3/9] drm/i915: Enable default_phase in GCP when possible

From: "Konduru, Chandra" <chandra.konduru@intel.com>
To: "ville.syrjala@linux.intel.com" <ville.syrjala@linux.intel.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH v2 3/9] drm/i915: Enable default_phase in GCP	when possible
Date: Mon, 1 Jun 2015 21:49:53 +0000	[thread overview]
Message-ID: <76A9B330A4D78C4D99CB292C4CC06C0E36FEEE4D@fmsmsx101.amr.corp.intel.com> (raw)
In-Reply-To: <1430834787-10255-4-git-send-email-ville.syrjala@linux.intel.com>

> -----Original Message-----
> From: Intel-gfx [mailto:intel-gfx-bounces@lists.freedesktop.org] On Behalf Of
> ville.syrjala@linux.intel.com
> Sent: Tuesday, May 05, 2015 7:06 AM
> To: intel-gfx@lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH v2 3/9] drm/i915: Enable default_phase in GCP when
> possible
> 
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> When the video timings are suitably aligned so that all different periods start at
> phase 0 (ie. none of the periods start mid-pixel) we can inform the sink about
> this. Supposedly the sink can then optimize certain things. Obviously this is only
> relevant when outputting >8bpc data since otherwise there are no mid-pixel
> phases.
> 
> v2: Rebased due to crtc->config changes
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 48
> +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> b/drivers/gpu/drm/i915/intel_hdmi.c
> index 87c4905..2e98e33 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -560,6 +560,49 @@ static bool hdmi_sink_is_deep_color(struct
> drm_encoder *encoder)
>  	return false;
>  }
> 
> +/*
> + * Determine if default_phase=1 can be indicated in the GCP infoframe.
> + *
> + * From HDMI specification 1.4a:
> + * - The first pixel of each Video Data Period shall always have a
> +pixel packing phase of 0
> + * - The first pixel following each Video Data Period shall have a
> +pixel packing phase of 0
> + * - The PP bits shall be constant for all GCPs and will be equal to
> +the last packing phase
> + * - The first pixel following every transition of HSYNC or VSYNC shall have a
> pixel packing
> + *   phase of 0
> + */
> +static bool gcp_default_phase_possible(int pipe_bpp,
> +				       const struct drm_display_mode *mode) {
> +	unsigned int pixels_per_group;
> +
> +	switch (pipe_bpp) {
> +	case 30:
> +		/* 4 pixels in 5 clocks */
> +		pixels_per_group = 4;
> +		break;
> +	case 36:
> +		/* 2 pixels in 3 clocks */
> +		pixels_per_group = 2;
> +		break;
> +	case 48:
> +		/* 1 pixel in 2 clocks */
> +		pixels_per_group = 1;
> +		break;
> +	default:
> +		/* phase information not relevant for 8bpc */
> +		return false;
> +	}
> +
> +	return mode->crtc_hdisplay % pixels_per_group == 0 &&
> +		mode->crtc_htotal % pixels_per_group == 0 &&
> +		mode->crtc_hblank_start % pixels_per_group == 0 &&
> +		mode->crtc_hblank_end % pixels_per_group == 0 &&
> +		mode->crtc_hsync_start % pixels_per_group == 0 &&
> +		mode->crtc_hsync_end % pixels_per_group == 0 &&

For hsync, bspec says Hsync is an even number.
Isn't it above check should be something like (hsync_end - hsync_start) % 2 == 0?
And similarly for front & back porches, right? 

> +		((mode->flags & DRM_MODE_FLAG_INTERLACE) == 0 ||
> +		 mode->crtc_htotal/2 % pixels_per_group == 0); }
> +
>  static bool intel_hdmi_set_gcp_infoframe(struct drm_encoder *encoder)  {
>  	struct drm_i915_private *dev_priv = encoder->dev->dev_private; @@ -
> 579,6 +622,11 @@ static bool intel_hdmi_set_gcp_infoframe(struct
> drm_encoder *encoder)
>  	if (hdmi_sink_is_deep_color(encoder))
>  		val |= GCP_COLOR_INDICATION;
> 
> +	/* Enable default_phase whenever the display mode is suitably aligned
> */
> +	if (gcp_default_phase_possible(crtc->config->pipe_bpp,
> +				       &crtc->config->base.adjusted_mode))
> +		val |= GCP_DEFAULT_PHASE_ENABLE;
> +
>  	I915_WRITE(reg, val);
> 
>  	return val != 0;
> --
> 2.0.5
> 
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