[Intel-gfx] [PATCH v2 1/2] drm/i915/glk: Apply cdclk workaround for DP audio

[Paulo Zanoni]

Em Ter, 2017-03-07 às 16:12 -0800, Dhinakaran Pandiyan escreveu:
> Implement the DP-Audio cdclk restriction for GLK, similar to what is
> implemented for BDW and other GEN9 platforms. The max. pixel clock
> adjustment for GLK, however factors in the 2 pixels per clock output
> that
> GLK generates.
> 
> Separating min. cdclk and max. pixel_rate would be nicer, but let's
> defer that to future and fix the GLK bug for now.

Looks correct to me.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

No cc:stable seems to be required due to GLK still being alpha_support.

> 
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_cdclk.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_cdclk.c
> b/drivers/gpu/drm/i915/intel_cdclk.c
> index de5ce6b..e8c1181 100644
> --- a/drivers/gpu/drm/i915/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> @@ -1442,16 +1442,21 @@ static int
> bdw_adjust_min_pipe_pixel_rate(struct intel_crtc_state *crtc_state,
>  	if (IS_BROADWELL(dev_priv) && crtc_state->ips_enabled)
>  		pixel_rate = DIV_ROUND_UP(pixel_rate * 100, 95);
>  
> -	/* BSpec says "Do not use DisplayPort with CDCLK less than
> -	 * 432 MHz, audio enabled, port width x4, and link rate
> -	 * HBR2 (5.4 GHz), or else there may be audio corruption or
> -	 * screen corruption."
> +	/* BSpec says "Do not use DisplayPort with CDCLK less than
> 432 MHz,
> +	 * audio enabled, port width x4, and link rate HBR2 (5.4
> GHz), or else
> +	 * there may be audio corruption or screen corruption." This
> cdclk
> +	 * restriction for GLK is 316.8 MHz and since GLK can output
> two
> +	 * pixels per clock, the pixel rate becomes 2 * 316.8 MHz.
>  	 */
>  	if (intel_crtc_has_dp_encoder(crtc_state) &&
>  	    crtc_state->has_audio &&
>  	    crtc_state->port_clock >= 540000 &&
> -	    crtc_state->lane_count == 4)
> -		pixel_rate = max(432000, pixel_rate);
> +	    crtc_state->lane_count == 4) {
> +		if (IS_GEMINILAKE(dev_priv))
> +			pixel_rate = max(2 * 316800, pixel_rate);
> +		else
> +			pixel_rate = max(432000, pixel_rate);
> +	}
>  
>  	return pixel_rate;
>  }