Re: [PATCH v5 03/15] drm/i915/alpm: alpm_init() for DP2.1

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Tue, 2026-08-25 at 11:15 +0530, Animesh Manna wrote:
> Initialize ALPM for DP2.1 and separate out ALPM mutex-init
> from alpm-init.
> 
> v2: Separate out mutex-init. [Jani]
> v3: Refactor further to avoid DISPLAY_VER check in multiple places.
> [Jani]
> V4: Cosmetic changes. [Suraj]
> 
> Cc: Jouni Högander <jouni.hogander@intel.com>
> Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_alpm.c | 13 +++++++++++++
>  drivers/gpu/drm/i915/display/intel_alpm.h |  1 +
>  drivers/gpu/drm/i915/display/intel_dp.c   |  8 ++++++--
>  3 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> b/drivers/gpu/drm/i915/display/intel_alpm.c
> index 542900e29a01..08ad77cd32f8 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> @@ -43,6 +43,19 @@ bool intel_alpm_is_alpm_aux_less(struct intel_dp
> *intel_dp,
>  		(crtc_state->has_lobf &&
> intel_alpm_aux_less_wake_supported(intel_dp));
>  }
>  
> +bool intel_alpm_source_supported(struct intel_connector *connector)
> +{
> +	struct intel_display *display = to_intel_display(connector);
> +
> +	if (!((connector->base.connector_type ==
> DRM_MODE_CONNECTOR_DisplayPort &&
> +	       DISPLAY_VER(display) >= 35) ||
> +	    (connector->base.connector_type ==
> DRM_MODE_CONNECTOR_eDP &&
> +	     DISPLAY_VER(display) >= 20)))

See drivers/gpu/drm/i915/display/intel_psr.c::_psr_init_dpcd. There
PSR2 is depending on sink ALPM support. Is correct version >= 9 or
maybe this helper should be just dropped.

> +		return false;
> +
> +	return true;
> +}
> +
>  void intel_alpm_init_dpcd(struct intel_dp *intel_dp)
>  {
>  	u8 dpcd;
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.h
> b/drivers/gpu/drm/i915/display/intel_alpm.h
> index fae68d557960..7280865ed5f0 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> @@ -15,6 +15,7 @@ struct intel_connector;
>  struct intel_atomic_state;
>  struct intel_crtc;
>  
> +bool intel_alpm_source_supported(struct intel_connector *connector);
>  void intel_alpm_init_dpcd(struct intel_dp *intel_dp);
>  void intel_alpm_init(struct intel_dp *intel_dp);
>  bool intel_alpm_compute_params(struct intel_dp *intel_dp,
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 77d516f0bd07..042c6e8b8e60 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6343,6 +6343,9 @@ intel_dp_detect(struct drm_connector
> *_connector,
>  	if (ret == 1)
>  		connector->base.epoch_counter++;
>  
> +	if (intel_alpm_source_supported(connector))
> +		intel_alpm_init_dpcd(intel_dp);

See my comment above. Sink DPCD capability could be read
unconditionally. If you want to keep this approach then you need to fix
intel_alpm_source_supported. Otherwise PSR2 breaks on display version <
20.

> +
>  	if (!intel_dp_is_edp(intel_dp))
>  		intel_psr_init_dpcd(intel_dp, connector);
>  
> @@ -6986,8 +6989,6 @@ static bool intel_edp_init_connector(struct
> intel_dp *intel_dp,
>  	 */
>  	intel_hpd_enable_detection(encoder);
>  
> -	intel_alpm_init(intel_dp);
> -
>  	/* Cache DPCD and EDID for edp. */
>  	has_dpcd = intel_edp_init_dpcd(intel_dp, connector);
>  
> @@ -7202,6 +7203,9 @@ intel_dp_init_connector(struct
> intel_digital_port *dig_port,
>  
>  	intel_psr_init(intel_dp);
>  
> +	if (intel_alpm_source_supported(connector))
> +		intel_alpm_init(intel_dp);

Same problem here. Another way could be to hide details into
intel_alpm_init and call intel_alpm_init unconditionally.

BR,
Jouni Högander

> +
>  	return true;
>  
>  fail: