Re: [PATCH v5 4/8] drm/i915/lobf: Update lobf if any change in dependent parameters

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

On Mon, 2025-03-03 at 14:05 +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]
> 
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_alpm.c | 18 ++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_alpm.h |  1 +
>  drivers/gpu/drm/i915/display/intel_ddi.c  |  1 +
>  3 files changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> b/drivers/gpu/drm/i915/display/intel_alpm.c
> index c2862888466f..f4586c76a7b7 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> @@ -312,6 +312,24 @@ void intel_alpm_lobf_compute_config(struct
> intel_dp *intel_dp,
>  		(first_sdp_position + waketime_in_lines);
>  }
>  
> +void intel_alpm_lobf_update(const struct intel_crtc_state
> *crtc_state)
> +{
> +	struct intel_display *display =
> to_intel_display(crtc_state);
> +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> +	u32 alpm_ctl;
> +
> +	if (DISPLAY_VER(display) < 20)
> +		return;
> +
> +	if (!crtc_state->has_lobf) {
> +		alpm_ctl = intel_de_read(display, ALPM_CTL(display,
> cpu_transcoder));
> +		if (alpm_ctl & ALPM_CTL_LOBF_ENABLE) {
> +			alpm_ctl &= ~ALPM_CTL_LOBF_ENABLE;
> +			intel_de_write(display, ALPM_CTL(display,
> cpu_transcoder), alpm_ctl);
> +		}

Why can't you do this in alpm_post_plane_update? Disable it there if
old_crtc_state->has_lobf && !new_crtc_state->has_lobf?

BR,

Jouni Högander

> +	}
> +}
> +
>  static void lnl_alpm_configure(struct intel_dp *intel_dp,
>  			       const struct intel_crtc_state
> *crtc_state)
>  {
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.h
> b/drivers/gpu/drm/i915/display/intel_alpm.h
> index 91f51fb24f98..c6efd25c2062 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> @@ -23,6 +23,7 @@ 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_lobf_update(const struct intel_crtc_state
> *crtc_state);
>  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_ddi.c
> b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 9b504dcfb446..b6186e1cf804 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3620,6 +3620,7 @@ static void intel_ddi_update_pipe_dp(struct
> intel_atomic_state *state,
>  	intel_ddi_set_dp_msa(crtc_state, conn_state);
>  
>  	intel_dp_set_infoframes(encoder, true, crtc_state,
> conn_state);
> +	intel_alpm_lobf_update(crtc_state);
>  
>  	intel_backlight_update(state, encoder, crtc_state,
> conn_state);
>  	drm_connector_update_privacy_screen(conn_state);