> 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-e80ff8959...@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
