RE: [PATCHv3] drm/i915/dp: On DPCD init wake the DPRx for eDP

> Subject: RE: [PATCHv3] drm/i915/dp: On DPCD init wake the DPRx for eDP
> 
> 
> -----Original Message-----
> From: Murthy, Arun R <[email protected]>
> Sent: 25 February 2026 11:41
> To: [email protected]; [email protected]
> Cc: Deak, Imre <[email protected]>; Kandpal, Suraj
> <[email protected]>; Nikula, Jani <[email protected]>;
> [email protected]; Murthy, Arun R <[email protected]>
> Subject: [PATCHv3] drm/i915/dp: On DPCD init wake the DPRx for eDP
> 
> Its observed that on AUX_CH failure, even if the retry is increased to 1000, it
> does not succeed. Either the command might be wrong or sink in an
> unknown/sleep state can cause this. So try waking the sink device.
> Before reading the DPCD caps wake the sink for eDP.
> 
> v2: Use poll_timeout_us (Jani N)
>     Add the reason, why this change is required (Ville)
> v3: Wake sink only for eDP
>     Remove the dpcd probe set to true/false in wake_sink (Imre)
> 
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/4391
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16654
> Signed-off-by: Arun R Murthy <[email protected]>

I think this reply messed up something in patchwork have a look. Moreover its not building anymore.

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 34 +++++++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_dp.h |  1 +
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 025e906b63a9..38ea4aad74de 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4705,6 +4705,38 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
>  	intel_edp_set_data_override_rates(intel_dp);
>  }
> 
> +/* Spec says to try for 3 times, its doubled to add the software overhead */
> +#define AUX_CH_WAKE_RETRY	6
> +
> +void intel_dp_wake_sink(struct intel_dp *intel_dp) {

Should this be renamed to intel_edp_wake_sink now that its used only for eDP
Also I think this function can be made static now.

> +	u8 value = 0;
> +	int ret = 0;
> +
> +	/*
> +	 * Wake the sink device
> +	 * Spec DP2.1 section 2.3.1.2 if AUX CH is powered down by writing
> 0x02
> +	 * to DP_SET_POWER dpcd reg, 1ms time would be required to wake it
> up
> +	 */
> +	ret = poll_timeout_us(ret = drm_dp_dpcd_readb(&intel_dp->aux,
> DP_SET_POWER, &value),

So we have recently switched from using drm_dp_dpcd_read/writeb to drm_dp_dpcd_read/write_byte I think you can have a look at usage and
Replace it with that function here.
Check https://lore.kernel.org/r/20250324-drm-rework-dpcd-access-v4-1-e80ff89593df@oss.qualcomm.com to see what that was required.

Regards,
Suraj Kandpal

> +			      ret > 0,
> +			      1000, AUX_CH_WAKE_RETRY * 1000, true);
> +
> +	/*
> +	 * If sink is in D3 then it may not respond to the AUX tx so
> +	 * wake it up to D3_AUX_ON state
> +	 * If the above poll_timeout_us fails, try waking the sink.
> +	 */
> +	if (value == DP_SET_POWER_D3 || ret < 0) {
> +		/* After setting to D0 need a min of 1ms to wake(Spec DP2.1
> sec 2.3.1.2) */
> +		drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER,
> +				   DP_SET_POWER_D0);
> +		fsleep(1000);
> +		drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER,
> +				   DP_SET_POWER_D3_AUX_ON);
> +	}
> +}
> +
>  static bool
>  intel_edp_init_dpcd(struct intel_dp *intel_dp, struct intel_connector
> *connector)  { @@ -4713,6 +4745,8 @@ intel_edp_init_dpcd(struct intel_dp
> *intel_dp, struct intel_connector *connector
>  	/* this function is meant to be called only once */
>  	drm_WARN_ON(display->drm, intel_dp->dpcd[DP_DPCD_REV] != 0);
> 
> +	intel_dp_wake_sink(intel_dp);
> +
>  	if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd) != 0)
>  		return false;
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> b/drivers/gpu/drm/i915/display/intel_dp.h
> index b0bbd5981f57..3f16077c0cc7 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -232,6 +232,7 @@ bool intel_dp_dotclk_valid(struct intel_display
> *display,  bool intel_dp_joiner_candidate_valid(struct intel_connector
> *connector,
>  				     int hdisplay,
>  				     int num_joined_pipes);
> +void intel_dp_wake_sink(struct intel_dp *intel_dp);
> 
>  #define for_each_joiner_candidate(__connector, __mode,
> __num_joined_pipes) \
>  	for ((__num_joined_pipes) = 1; (__num_joined_pipes) <=
> (I915_MAX_PIPES); (__num_joined_pipes)++) \
> --
> 2.25.1