Re: [PATCH] drm/i915: Fix pipe_bpp readout for BXT/GLK DSI

From: Imre Deak <imre.deak@intel.com>
To: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Fix pipe_bpp readout for BXT/GLK DSI
Date: Fri, 5 Apr 2019 19:23:35 +0300	[thread overview]
Message-ID: <20190405162335.GC13716@ideak-desk.fi.intel.com> (raw)
In-Reply-To: <20190405141349.11950-1-ville.syrjala@linux.intel.com>

On Fri, Apr 05, 2019 at 05:13:49PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The only bpc information in pipe registers for BXT/GLK DSI
> is the PIPEMISC dither bpc. Let's try to use that to read
> out pipe_bpp on these platforms. However, I'm not sure if
> this will be correctly populated by the GOP since bspec
> suggests it's only needed if dithering is actually enabled.
> If not I guess we'll have to go one step further and
> extract pipe_bpp from the DSI pixel format when dithering
> is disabled.
> 
> Cc: Hans de Goede <hdegoede@redhat.com>
> Fixes: ca0b04db14a5 ("drm/i915/dsi: Fix pipe_bpp for handling for 6 bpc pixel-formats")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

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

> ---
>  drivers/gpu/drm/i915/vlv_dsi.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/vlv_dsi.c b/drivers/gpu/drm/i915/vlv_dsi.c
> index 0a950c976bbb..6898541403a2 100644
> --- a/drivers/gpu/drm/i915/vlv_dsi.c
> +++ b/drivers/gpu/drm/i915/vlv_dsi.c
> @@ -256,6 +256,28 @@ static void band_gap_reset(struct drm_i915_private *dev_priv)
>  	mutex_unlock(&dev_priv->sb_lock);
>  }
>  
> +static int bdw_get_pipemisc_bpp(struct intel_crtc *crtc)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> +	u32 tmp;
> +
> +	tmp = I915_READ(PIPEMISC(crtc->pipe));
> +
> +	switch (tmp & PIPEMISC_DITHER_BPC_MASK) {
> +	case PIPEMISC_DITHER_6_BPC:
> +		return 18;
> +	case PIPEMISC_DITHER_8_BPC:
> +		return 24;
> +	case PIPEMISC_DITHER_10_BPC:
> +		return 30;
> +	case PIPEMISC_DITHER_12_BPC:
> +		return 36;
> +	default:
> +		MISSING_CASE(tmp);
> +		return 0;
> +	}
> +}
> +
>  static int intel_dsi_compute_config(struct intel_encoder *encoder,
>  				    struct intel_crtc_state *pipe_config,
>  				    struct drm_connector_state *conn_state)
> @@ -1082,6 +1104,8 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
>  	bpp = mipi_dsi_pixel_format_to_bpp(
>  			pixel_format_from_register_bits(fmt));
>  
> +	pipe_config->pipe_bpp = bdw_get_pipemisc_bpp(crtc);
> +
>  	/* Enable Frame time stamo based scanline reporting */
>  	adjusted_mode->private_flags |=
>  			I915_MODE_FLAG_GET_SCANLINE_FROM_TIMESTAMP;
> -- 
> 2.19.2
> 
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