Re: [PATCH] drm/i915: Implement display w/a #1143

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Jan 19, 2018 at 06:45:49PM +0000, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Apparently SKL/KBL need some manual help to get the
> programmed HDMI vswing to stick. Implement the relevant
> workaround (display w/a #1143).
> 
> Note that the relevant chicken bits live in a transcoder register
> even though the bits affect a specific DDI port rather than a
> specific transcoder. Hence we must pick the correct transcoder
> register instance based on the port rather than based on the
> cpu_transcoder.
> 
> Also note that for completeness I included support for DDI A/E
> in the code even though we never have HDMI on those ports.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h  |  8 ++++++--
>  drivers/gpu/drm/i915/intel_ddi.c | 42 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 10e1269ad6af..2e6d0dc01dc7 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7012,8 +7012,12 @@ enum {
>  #define CHICKEN_TRANS_A         0x420c0
>  #define CHICKEN_TRANS_B         0x420c4
>  #define CHICKEN_TRANS(trans) _MMIO_TRANS(trans, CHICKEN_TRANS_A, CHICKEN_TRANS_B)
> -#define PSR2_VSC_ENABLE_PROG_HEADER    (1<<12)
> -#define PSR2_ADD_VERTICAL_LINE_COUNT   (1<<15)
> +#define  DDI_TRAINING_OVERRIDE_ENABLE	(1<<19)
> +#define  DDI_TRAINING_OVERRIDE_VALUE	(1<<18)
> +#define  DDIE_TRAINING_OVERRIDE_ENABLE	(1<<17) /* CHICKEN_TRANS_A only */
> +#define  DDIE_TRAINING_OVERRIDE_VALUE	(1<<16) /* CHICKEN_TRANS_A only */

Wa on Bspec doesnt mention port E, although it makes sense to have...
maybe a WARN_ON if DDIE but not TRANS_A then?!

> +#define  PSR2_ADD_VERTICAL_LINE_COUNT   (1<<15)
> +#define  PSR2_VSC_ENABLE_PROG_HEADER    (1<<12)
>  
>  #define DISP_ARB_CTL	_MMIO(0x45000)
>  #define  DISP_FBC_MEMORY_WAKE		(1<<31)
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 6260a882fbe4..7b1ab003279f 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2433,6 +2433,48 @@ static void intel_enable_ddi_hdmi(struct intel_encoder *encoder,
>  					  crtc_state->hdmi_high_tmds_clock_ratio,
>  					  crtc_state->hdmi_scrambling);
>  
> +	/* Display WA #1143: skl,kbl */
> +	if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) {

on KBL, but not on CFL?! Strange... Art?

> +		/*
> +		 * For some reason these chicken bits have been
> +		 * stuffed into a transcoder register, event though
> +		 * the bits affect a specific DDI port rather than
> +		 * a specific transcoder.
> +		 */
> +		static const enum transcoder port_to_transcoder[] = {
> +			[PORT_A] = TRANSCODER_EDP,
> +			[PORT_B] = TRANSCODER_A,
> +			[PORT_C] = TRANSCODER_B,
> +			[PORT_D] = TRANSCODER_C,
> +			[PORT_E] = TRANSCODER_A,
> +		};
> +		enum transcoder transcoder = port_to_transcoder[port];
> +		u32 val;
> +
> +		val = I915_READ(CHICKEN_TRANS(transcoder));
> +
> +		if (port == PORT_E)
> +			val |= DDIE_TRAINING_OVERRIDE_ENABLE |
> +				DDIE_TRAINING_OVERRIDE_VALUE;
> +		else
> +			val |= DDI_TRAINING_OVERRIDE_ENABLE |
> +				DDI_TRAINING_OVERRIDE_VALUE;
> +
> +		I915_WRITE(CHICKEN_TRANS(transcoder), val);
> +		POSTING_READ(CHICKEN_TRANS(transcoder));
> +
> +		udelay(1);
> +
> +		if (port == PORT_E)
> +			val &= ~(DDIE_TRAINING_OVERRIDE_ENABLE |
> +				 DDIE_TRAINING_OVERRIDE_VALUE);
> +		else
> +			val &= ~(DDI_TRAINING_OVERRIDE_ENABLE |
> +				 DDI_TRAINING_OVERRIDE_VALUE);
> +
> +		I915_WRITE(CHICKEN_TRANS(transcoder), val);
> +	}
> +
>  	/* In HDMI/DVI mode, the port width, and swing/emphasis values
>  	 * are ignored so nothing special needs to be done besides
>  	 * enabling the port.
> -- 
> 2.13.6
> 
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