Re: [RFC PATCH 2/2] drm/i915/bxt: Adjusting the error in horizontal timings retrieval

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Apr 19, 2016 at 01:48:14PM +0530, Ramalingam C wrote:
> In BXT DSI there is no regs programmed with few horizontal timings
> in Pixels but txbyteclkhs.. So retrieval process adds some
> ROUND_UP ERRORS in the process of PIXELS<==>txbyteclkhs.
> 
> Actually here for the given adjusted_mode, we are calculating the
> value programmed to the port and then back to the horizontal timing
> param in pixels. This is the expected value at the end of get_config,
> including roundup errors. And if that is same as retrieved value
> from port, then retrieved (HW state) adjusted_mode's horizontal
> timings are corrected to match with SW state to nullify the errors.
> 
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>

I didn't check the details, but I think this is the fix we want. Still
needs in-depth review, and some testing on a few different dsi bxt
machines just to make sure I think, but on both patches:

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Cheers, Daniel
> ---
>  drivers/gpu/drm/i915/intel_dsi.c |   97 ++++++++++++++++++++++++++++++++++----
>  1 file changed, 88 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index e0259e6..8a1b872 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -46,6 +46,14 @@ static const struct {
>  	},
>  };
>  
> +/* return pixels in terms of txbyteclkhs */
> +static u16 txbyteclkhs(u16 pixels, int bpp, int lane_count,
> +		       u16 burst_mode_ratio)
> +{
> +	return DIV_ROUND_UP(DIV_ROUND_UP(pixels * bpp * burst_mode_ratio,
> +					 8 * 100), lane_count);
> +}
> +
>  /* return pixels equvalent to txbyteclkhs */
>  static u16 pixels_from_txbyteclkhs(u16 clk_hs, int bpp, int lane_count,
>  			u16 burst_mode_ratio)
> @@ -779,11 +787,19 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_display_mode *adjusted_mode =
>  					&pipe_config->base.adjusted_mode;
> +	struct drm_display_mode *adjusted_mode_sw;
> +	struct intel_crtc *intel_crtc;
>  	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
>  	unsigned int lane_count = intel_dsi->lane_count;
>  	unsigned int bpp, fmt;
>  	enum port port;
>  	u16 hactive, hfp, hsync, hbp, vfp, vsync, vbp;
> +	u16 hfp_sw, hsync_sw, hbp_sw;
> +	u16 crtc_htotal_sw, crtc_hsync_start_sw, crtc_hsync_end_sw,
> +				crtc_hblank_start_sw, crtc_hblank_end_sw;
> +
> +	intel_crtc = to_intel_crtc(encoder->base.crtc);
> +	adjusted_mode_sw = &intel_crtc->config->base.adjusted_mode;
>  
>  	/*
>  	 * Atleast one port is active as encoder->get_config called only if
> @@ -847,8 +863,79 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
>  	adjusted_mode->crtc_vsync_end = vsync + adjusted_mode->crtc_vsync_start;
>  	adjusted_mode->crtc_vblank_start = adjusted_mode->crtc_vdisplay;
>  	adjusted_mode->crtc_vblank_end = adjusted_mode->crtc_vtotal;
> -}
>  
> +	/*
> +	 * In BXT DSI there is no regs programmed with few horizontal timings
> +	 * in Pixels but txbyteclkhs.. So retrieval process adds some
> +	 * ROUND_UP ERRORS in the process of PIXELS<==>txbyteclkhs.
> +	 * Actually here for the given adjusted_mode, we are calculating the
> +	 * value programmed to the port and then back to the horizontal timing
> +	 * param in pixels. This is the expected value, including roundup errors
> +	 * And if that is same as retrieved value from port, then
> +	 * (HW state) adjusted_mode's horizontal timings are corrected to
> +	 * match with SW state to nullify the errors.
> +	 */
> +	/* Calculating the value programmed to the Port register */
> +	hfp_sw = adjusted_mode_sw->crtc_hsync_start -
> +					adjusted_mode_sw->crtc_hdisplay;
> +	hsync_sw = adjusted_mode_sw->crtc_hsync_end -
> +					adjusted_mode_sw->crtc_hsync_start;
> +	hbp_sw = adjusted_mode_sw->crtc_htotal -
> +					adjusted_mode_sw->crtc_hsync_end;
> +
> +	if (intel_dsi->dual_link) {
> +		hfp_sw /= 2;
> +		hsync_sw /= 2;
> +		hbp_sw /= 2;
> +	}
> +
> +	hfp_sw = txbyteclkhs(hfp_sw, bpp, lane_count,
> +						intel_dsi->burst_mode_ratio);
> +	hsync_sw = txbyteclkhs(hsync_sw, bpp, lane_count,
> +			    intel_dsi->burst_mode_ratio);
> +	hbp_sw = txbyteclkhs(hbp_sw, bpp, lane_count,
> +						intel_dsi->burst_mode_ratio);
> +
> +	/* Reverse calculating the adjusted mode parameters from port reg vals*/
> +	hfp_sw = pixels_from_txbyteclkhs(hfp_sw, bpp, lane_count,
> +						intel_dsi->burst_mode_ratio);
> +	hsync_sw = pixels_from_txbyteclkhs(hsync_sw, bpp, lane_count,
> +						intel_dsi->burst_mode_ratio);
> +	hbp_sw = pixels_from_txbyteclkhs(hbp_sw, bpp, lane_count,
> +						intel_dsi->burst_mode_ratio);
> +
> +	if (intel_dsi->dual_link) {
> +		hfp_sw *= 2;
> +		hsync_sw *= 2;
> +		hbp_sw *= 2;
> +	}
> +
> +	crtc_htotal_sw = adjusted_mode_sw->crtc_hdisplay + hfp_sw +
> +							hsync_sw + hbp_sw;
> +	crtc_hsync_start_sw = hfp_sw + adjusted_mode_sw->crtc_hdisplay;
> +	crtc_hsync_end_sw = hsync_sw + crtc_hsync_start_sw;
> +	crtc_hblank_start_sw = adjusted_mode_sw->crtc_hdisplay;
> +	crtc_hblank_end_sw = crtc_htotal_sw;
> +
> +	if (adjusted_mode->crtc_htotal == crtc_htotal_sw)
> +		adjusted_mode->crtc_htotal = adjusted_mode_sw->crtc_htotal;
> +
> +	if (adjusted_mode->crtc_hsync_start == crtc_hsync_start_sw)
> +		adjusted_mode->crtc_hsync_start =
> +					adjusted_mode_sw->crtc_hsync_start;
> +
> +	if (adjusted_mode->crtc_hsync_end == crtc_hsync_end_sw)
> +		adjusted_mode->crtc_hsync_end =
> +					adjusted_mode_sw->crtc_hsync_end;
> +
> +	if (adjusted_mode->crtc_hblank_start == crtc_hblank_start_sw)
> +		adjusted_mode->crtc_hblank_start =
> +					adjusted_mode_sw->crtc_hblank_start;
> +
> +	if (adjusted_mode->crtc_hblank_end == crtc_hblank_end_sw)
> +		adjusted_mode->crtc_hblank_end =
> +					adjusted_mode_sw->crtc_hblank_end;
> +}
>  
>  static void intel_dsi_get_config(struct intel_encoder *encoder,
>  				 struct intel_crtc_state *pipe_config)
> @@ -917,14 +1004,6 @@ static u16 txclkesc(u32 divider, unsigned int us)
>  	}
>  }
>  
> -/* return pixels in terms of txbyteclkhs */
> -static u16 txbyteclkhs(u16 pixels, int bpp, int lane_count,
> -		       u16 burst_mode_ratio)
> -{
> -	return DIV_ROUND_UP(DIV_ROUND_UP(pixels * bpp * burst_mode_ratio,
> -					 8 * 100), lane_count);
> -}
> -
>  static void set_dsi_timings(struct drm_encoder *encoder,
>  			    const struct drm_display_mode *adjusted_mode)
>  {
> -- 
> 1.7.9.5

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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