Re: [Intel-gfx] [PATCH 2/2] drm/i915/display: Implement Wa_16013835468

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Thu, Feb 10, 2022 at 10:52:23AM -0800, José Roberto de Souza wrote:
> PSR2 workaround required when mode has delayed vblank.
> 
> BSpec: 52890
> BSpec: 49421
> Cc: Jouni Högander <jouni.hogander@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>


I think we better implement it in a more generic way.
BSpec 71580 formulates this workaround more precisely:

"
If any low power watermark is disabled because the package C state 
has too much latency for the size of Vblank and PSR1 or PSR2 is enabled, 
set the register bit for this pipe (listing below) to 1 to disable a 
PSR optimization to override to the maximum watermark. 
Clear the bit if the size of Vblank does not require low power watermarks to be disabled 
or PSR* is disabled."


Pipe A 0x46430 bit 23

Pipe B 0x46430 bit 24

Pipe C 0x46430 bit 25

Pipe D 0x46430 bit 31


TRANS_SET_CONTEXT_LATENCY is used to delay the vblank"


Almost we must ensure that one:

Vblank time >= MAX(framestart delay + package C state latency + watermark 0 time + pipe scaler pre-fill time + DSC pre-fill time, 
                   PSR2 vblank time, SDP vblank time)

Line time >= PSR2 line time

I'm currently working on the latter one. I have suggestion that one I finish 
with calculations required for this formula, I can provide some api for this
patch in order to check if PSR can be enabled and workaround has to be applied.

Stan


> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 40 ++++++++++++++++++++++--
>  drivers/gpu/drm/i915/i915_reg.h          | 13 +++++---
>  2 files changed, 46 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 72bd8d3261e0c..2e0b092f4b6be 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1063,7 +1063,23 @@ static void intel_psr_activate(struct intel_dp *intel_dp)
>  	intel_dp->psr.active = true;
>  }
>  
> -static void intel_psr_enable_source(struct intel_dp *intel_dp)
> +static u32 wa_16013835468_bit_get(struct intel_dp *intel_dp)
> +{
> +	switch (intel_dp->psr.pipe) {
> +	case PIPE_A:
> +		return LATENCY_REPORTING_REMOVED_PIPE_A;
> +	case PIPE_B:
> +		return LATENCY_REPORTING_REMOVED_PIPE_B;
> +	case PIPE_C:
> +		return LATENCY_REPORTING_REMOVED_PIPE_C;
> +	default:
> +		MISSING_CASE(intel_dp->psr.pipe);
> +		return 0;
> +	}
> +}
> +
> +static void intel_psr_enable_source(struct intel_dp *intel_dp,
> +				    const struct intel_crtc_state *crtc_state)
>  {
>  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
>  	enum transcoder cpu_transcoder = intel_dp->psr.transcoder;
> @@ -1133,6 +1149,20 @@ static void intel_psr_enable_source(struct intel_dp *intel_dp)
>  		if (IS_ALDERLAKE_P(dev_priv))
>  			intel_de_rmw(dev_priv, CLKGATE_DIS_MISC, 0,
>  				     CLKGATE_DIS_MISC_DMASC_GATING_DIS);
> +
> +		/* Wa_16013835468:tgl[b0+], dg1 */
> +		if (IS_TGL_DISPLAY_STEP(dev_priv, STEP_B0, STEP_FOREVER) ||
> +		    IS_DG1(dev_priv)) {
> +			u16 vtotal, vblank;
> +
> +			vtotal = crtc_state->uapi.adjusted_mode.crtc_vtotal -
> +				 crtc_state->uapi.adjusted_mode.crtc_vdisplay;
> +			vblank = crtc_state->uapi.adjusted_mode.crtc_vblank_end -
> +				 crtc_state->uapi.adjusted_mode.crtc_vblank_start;
> +			if (vblank > vtotal)
> +				intel_de_rmw(dev_priv, GEN8_CHICKEN_DCPR_1, 0,
> +					     wa_16013835468_bit_get(intel_dp));
> +		}
>  	}
>  }
>  
> @@ -1198,7 +1228,7 @@ static void intel_psr_enable_locked(struct intel_dp *intel_dp,
>  	intel_write_dp_vsc_sdp(encoder, crtc_state, &crtc_state->psr_vsc);
>  	intel_snps_phy_update_psr_power_state(dev_priv, phy, true);
>  	intel_psr_enable_sink(intel_dp);
> -	intel_psr_enable_source(intel_dp);
> +	intel_psr_enable_source(intel_dp, crtc_state);
>  	intel_dp->psr.enabled = true;
>  	intel_dp->psr.paused = false;
>  
> @@ -1297,6 +1327,12 @@ static void intel_psr_disable_locked(struct intel_dp *intel_dp)
>  		if (IS_ALDERLAKE_P(dev_priv))
>  			intel_de_rmw(dev_priv, CLKGATE_DIS_MISC,
>  				     CLKGATE_DIS_MISC_DMASC_GATING_DIS, 0);
> +
> +		/* Wa_16013835468:tgl[b0+], dg1 */
> +		if (IS_TGL_DISPLAY_STEP(dev_priv, STEP_B0, STEP_FOREVER) ||
> +		    IS_DG1(dev_priv))
> +			intel_de_rmw(dev_priv, GEN8_CHICKEN_DCPR_1,
> +				     wa_16013835468_bit_get(intel_dp), 0);
>  	}
>  
>  	intel_snps_phy_update_psr_power_state(dev_priv, phy, false);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 87c92314ee269..1cd4056400b63 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -6040,11 +6040,14 @@
>  #define HSW_NDE_RSTWRN_OPT	_MMIO(0x46408)
>  #define  RESET_PCH_HANDSHAKE_ENABLE	(1 << 4)
>  
> -#define GEN8_CHICKEN_DCPR_1		_MMIO(0x46430)
> -#define   SKL_SELECT_ALTERNATE_DC_EXIT	REG_BIT(30)
> -#define   ICL_DELAY_PMRSP		REG_BIT(22)
> -#define   DISABLE_FLR_SRC		REG_BIT(15)
> -#define   MASK_WAKEMEM			REG_BIT(13)
> +#define GEN8_CHICKEN_DCPR_1			_MMIO(0x46430)
> +#define   SKL_SELECT_ALTERNATE_DC_EXIT		REG_BIT(30)
> +#define   LATENCY_REPORTING_REMOVED_PIPE_C	REG_BIT(25)
> +#define   LATENCY_REPORTING_REMOVED_PIPE_B	REG_BIT(24)
> +#define   LATENCY_REPORTING_REMOVED_PIPE_A	REG_BIT(23)
> +#define   ICL_DELAY_PMRSP			REG_BIT(22)
> +#define   DISABLE_FLR_SRC			REG_BIT(15)
> +#define   MASK_WAKEMEM				REG_BIT(13)
>  
>  #define GEN11_CHICKEN_DCPR_2			_MMIO(0x46434)
>  #define   DCPR_MASK_MAXLATENCY_MEMUP_CLR	REG_BIT(27)
> -- 
> 2.35.1
>