[PATCH v9 06/10] drm/i915/lobf: Update lobf if any change in dependent parameters

[Hogander, Jouni]

On Thu, 2025-04-17 at 15:11 +0530, Animesh Manna wrote:
> For every commit the dependent condition for LOBF is checked
> and accordingly update has_lobf flag which will be used
> to update the ALPM_CTL register during commit.
> 
> v1: Initial version.
> v2: Avoid reading h/w register without has_lobf check. [Jani]
> v3: Update LOBF in post plane update instead of separate function.
> [Jouni]
> v4:
> - Add lobf disable print. [Jouni]
> - Simplify condition check for enabling/disabling lobf. [Jouni]
> v5: Disable LOBF in pre_plane_update(). [Jouni]
> 
> Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_alpm.c    | 43
> +++++++++++++++++++-
>  drivers/gpu/drm/i915/display/intel_alpm.h    |  2 +
>  drivers/gpu/drm/i915/display/intel_display.c |  1 +
>  3 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> b/drivers/gpu/drm/i915/display/intel_alpm.c
> index 01949b90c0c3..3fbe8eca1301 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> @@ -376,15 +376,56 @@ void intel_alpm_configure(struct intel_dp
> *intel_dp,
>  	intel_dp->alpm_parameters.transcoder = crtc_state-
> >cpu_transcoder;
>  }
>  
> +void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
> +				 struct intel_crtc *crtc)
> +{
> +	struct intel_display *display = to_intel_display(state);
> +	const struct intel_crtc_state *crtc_state =
> +		intel_atomic_get_new_crtc_state(state, crtc);
> +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> +	struct intel_encoder *encoder;
> +	u32 alpm_ctl;
> +
> +	if (DISPLAY_VER(display) < 20)
> +		return;
> +
> +	if (crtc_state->has_lobf)
> +		return;
> +
> +	for_each_intel_encoder_mask(display->drm, encoder,
> +				    crtc_state->uapi.encoder_mask) {
> +		struct intel_dp *intel_dp;
> +
> +		if (!intel_encoder_is_dp(encoder))
> +			continue;
> +
> +		intel_dp = enc_to_intel_dp(encoder);
> +
> +		if (!intel_dp_is_edp(intel_dp))
> +			continue;
> +
> +		alpm_ctl = intel_de_read(display, ALPM_CTL(display,
> cpu_transcoder));

How about if instead of reading you would rely on old_crtc_state-
>has_lobf as is done in intel_alpm_post_plane_update ? I think you can
write 0 into ALPM_CTL. Parameters are anyways written in
intel_alpm_post_plane_update when ALPM is enable for LOBF or PSR.

BR,

Jouni Högander
> +
> +		if (alpm_ctl & ALPM_CTL_LOBF_ENABLE) {
> +			alpm_ctl &= ~ALPM_CTL_LOBF_ENABLE;
> +			intel_de_write(display, ALPM_CTL(display,
> cpu_transcoder), alpm_ctl);
> +			drm_dbg_kms(display->drm, "Link off between
> frames (LOBF) disabled\n");
> +		}
> +	}
> +}
> +
>  void intel_alpm_post_plane_update(struct intel_atomic_state *state,
>  				  struct intel_crtc *crtc)
>  {
>  	struct intel_display *display = to_intel_display(state);
>  	const struct intel_crtc_state *crtc_state =
>  		intel_atomic_get_new_crtc_state(state, crtc);
> +	const struct intel_crtc_state *old_crtc_state =
> +		intel_atomic_get_old_crtc_state(state, crtc);
>  	struct intel_encoder *encoder;
>  
> -	if (!crtc_state->has_lobf && !crtc_state->has_psr)
> +	if ((!crtc_state->has_lobf ||
> +	     crtc_state->has_lobf == old_crtc_state->has_lobf) &&
> !crtc_state->has_psr)
>  		return;
>  
>  	for_each_intel_encoder_mask(display->drm, encoder,
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.h
> b/drivers/gpu/drm/i915/display/intel_alpm.h
> index 91f51fb24f98..77bae022a0ea 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> @@ -23,6 +23,8 @@ void intel_alpm_lobf_compute_config(struct intel_dp
> *intel_dp,
>  				    struct drm_connector_state
> *conn_state);
>  void intel_alpm_configure(struct intel_dp *intel_dp,
>  			  const struct intel_crtc_state
> *crtc_state);
> +void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
> +				 struct intel_crtc *crtc);
>  void intel_alpm_post_plane_update(struct intel_atomic_state *state,
>  				  struct intel_crtc *crtc);
>  void intel_alpm_lobf_debugfs_add(struct intel_connector *connector);
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index 96a95bc9d5bf..f91401ebdd1a 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -1177,6 +1177,7 @@ static void intel_pre_plane_update(struct
> intel_atomic_state *state,
>  		intel_atomic_get_new_crtc_state(state, crtc);
>  	enum pipe pipe = crtc->pipe;
>  
> +	intel_alpm_pre_plane_update(state, crtc);
>  	intel_psr_pre_plane_update(state, crtc);
>  
>  	if (intel_crtc_vrr_disabling(state, crtc)) {