[PATCH 2/2] drm/i915/lttpr: Enable Extended Wake Timeout

[Dmitry Baryshkov]

On Fri, Jan 17, 2025 at 11:18:50AM +0530, Suraj Kandpal wrote:
> Usually retimers take around 30 to 40ms to exit all devices from
> sleep state. Extended wake timeout request helps to give additional
> time by reading the DPCD register through which sink requests the
> minimal amount of time required to wake the sink up.
> Source  device shall keep retying  the AUX tansaction till the extended
> timeout that is being granted for LTTPRs from the sink device
> 
> --v2
> -Grant the requested time only if greater than 1ms [Arun]
> -Reframe commit message [Arun]
> 
> Spec: DP v2.1 Section 3.6.12.3
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c      |  2 +
>  .../drm/i915/display/intel_dp_link_training.c | 49 +++++++++++++++++++
>  .../drm/i915/display/intel_dp_link_training.h |  1 +
>  3 files changed, 52 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index acb986bc1f33..96cabe618678 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -2645,6 +2645,8 @@ static void mtl_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  	if (!is_mst)
>  		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
>  
> +	intel_dp_lttpr_wake_timeout_setup(intel_dp);
> +
>  	intel_dp_configure_protocol_converter(intel_dp, crtc_state);
>  	if (!is_mst)
>  		intel_dp_sink_enable_decompression(state,
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index 8b1977cfec50..c113b0be259e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -135,6 +135,55 @@ static bool intel_dp_lttpr_transparent_mode_enabled(struct intel_dp *intel_dp)
>  		DP_PHY_REPEATER_MODE_TRANSPARENT;
>  }
>  
> +void intel_dp_lttpr_wake_timeout_setup(struct intel_dp *intel_dp)

Please move this function to drivers/gpu/drm/display/drm_dp_helper.c
Except for the intel_dp_lttpr_transparent_mode_enabled() call there is
nothing Intel-specific there.

> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +	u8 val = 1;
> +	int ret;
> +
> +	if (intel_dp_lttpr_transparent_mode_enabled(intel_dp)) {
> +		static const u8 timeout_mapping[] = {
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_1_MS] = 1,
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_20_MS] = 20,
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_40_MS] = 40,
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_20_MS] = 20,
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_80_MS] = 80,
> +			[DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_100_MS] = 100,
> +		};
> +
> +		ret = drm_dp_dpcd_readb(&intel_dp->aux,
> +					DP_EXTENDED_DPRX_SLEEP_WAKE_TIMEOUT_REQUEST, &val);
> +		if (ret != 1) {
> +			drm_dbg_kms(display->drm,
> +				    "Failed to read Extended sleep wake timeout request\n");
> +			return;
> +		}
> +
> +		val = (val < sizeof(timeout_mapping) && timeout_mapping[val]) ?
> +			timeout_mapping[val] : 1;
> +
> +		if (val > 1)
> +			drm_dp_dpcd_writeb(&intel_dp->aux,
> +					   DP_EXTENDED_DPRX_SLEEP_WAKE_TIMEOUT_GRANT,
> +					   DP_DPRX_SLEEP_WAKE_TIMEOUT_PERIOD_GRANTED);
> +	} else {
> +		ret = drm_dp_dpcd_readb(&intel_dp->aux,
> +					DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT, &val);
> +		if (ret != 1) {
> +			drm_dbg_kms(display->drm,
> +				    "Failed to read Extended sleep wake timeout request\n");
> +			return;
> +		}
> +
> +		val = (val & DP_EXTENDED_WAKE_TIMEOUT_REQUEST_MASK) ?
> +			(val & DP_EXTENDED_WAKE_TIMEOUT_REQUEST_MASK) * 10 : 1;
> +
> +		if (val > 1)
> +			drm_dp_dpcd_writeb(&intel_dp->aux, DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT,
> +					   DP_EXTENDED_WAKE_TIMEOUT_GRANT);
> +	}
> +}
> +
>  /*
>   * Read the LTTPR common capabilities and switch the LTTPR PHYs to
>   * non-transparent mode if this is supported. Preserve the
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.h b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> index 2066b9146762..cd4e0d6db6ed 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> @@ -15,6 +15,7 @@ struct intel_dp;
>  
>  int intel_dp_read_dprx_caps(struct intel_dp *intel_dp, u8 dpcd[DP_RECEIVER_CAP_SIZE]);
>  int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp);
> +void intel_dp_lttpr_wake_timeout_setup(struct intel_dp *intel_dp);
>  
>  void intel_dp_link_training_set_mode(struct intel_dp *intel_dp,
>  				     int link_rate, bool is_vrr);
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry