[PATCH 5/9] drm/i915/dmc: Reload pipe DMC state on TGL when enabling pipe A

[Shankar, Uma]

> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, June 11, 2025 9:23 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: intel-xe at lists.freedesktop.org
> Subject: [PATCH 5/9] drm/i915/dmc: Reload pipe DMC state on TGL when
> enabling pipe A

I guess its applicable for all pipes and not just limited to A.

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On TGL/derivatives the entire pipe DMC state (program + MMIO) is lost when
> PG1 is disabled, and the main DMC does not restore any of it. Reload the state
> when enabling a pipe.

It is just the TGL or any other platforms affected ?
Current change looks fine though.

Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> The other option would be to not load the pipe DMC at all since it's only needed for
> "fast LACE" (which we don't use) on these platforms. But let's keep it around just
> in case we ever decide that "fast LACE" is something we want.

I agree, it's good to keep it.

> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dmc.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c
> b/drivers/gpu/drm/i915/display/intel_dmc.c
> index 331db28039db..fd99c4645260 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.c
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.c
> @@ -599,6 +599,12 @@ static void dmc_load_program(struct intel_display
> *display,
>  	}
>  }
> 
> +static bool need_pipedmc_load_program(struct intel_display *display) {
> +	/* On TGL/derivatives pipe DMC state is lost when PG1 is disabled */
> +	return DISPLAY_VER(display) == 12;
> +}
> +
>  void intel_dmc_enable_pipe(struct intel_display *display, enum pipe pipe)  {
>  	enum intel_dmc_id dmc_id = PIPE_TO_DMC_ID(pipe); @@ -606,6 +612,9
> @@ void intel_dmc_enable_pipe(struct intel_display *display, enum pipe pipe)
>  	if (!is_valid_dmc_id(dmc_id) || !has_dmc_id_fw(display, dmc_id))
>  		return;
> 
> +	if (need_pipedmc_load_program(display))
> +		dmc_load_program(display, dmc_id);
> +
>  	if (DISPLAY_VER(display) >= 20) {
>  		intel_de_write(display, PIPEDMC_INTERRUPT(pipe),
> pipedmc_interrupt_mask(display));
>  		intel_de_write(display, PIPEDMC_INTERRUPT_MASK(pipe),
> ~pipedmc_interrupt_mask(display));
> --
> 2.49.0