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

["Vodapalli, Ravi Kumar" <ravi.kumar.vodapalli@intel.com>]

On 12/13/2024 11:33 AM, 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 and giving the
> same amount of wait requested by sink device.
> Spec: DP v2.1 Section 3.6.12.3
>
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_ddi.c      |  2 +
>   .../drm/i915/display/intel_dp_link_training.c | 46 +++++++++++++++++++
>   .../drm/i915/display/intel_dp_link_training.h |  1 +
>   3 files changed, 49 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 4f9c50996446..d092c3ba0ccf 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -2624,6 +2624,8 @@ 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 ea9b4730a176..d0f0da78794e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -134,6 +134,52 @@ 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)
> +{
> +	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;

Returning from function without return type, better to declare int in 
place of void and return the error  value.

int intel_dp_lttpr_wake_timeout_setup(struct intel_dp *intel_dp)


Regards,
Ravi Kumar V
> +		}
> +
> +		val = (val < sizeof(timeout_mapping) && timeout_mapping[val]) ?
> +			timeout_mapping[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;
> +
> +		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);