drm/i915/dmc: Reload pipe DMC state on TGL when enabling pipe A

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.

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.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250617170759.19552-6-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c b/drivers/gpu/drm/i915/display/intel_dmc.c
index d933f82ffbeed00983a5bbe39dd9b2924a76936e..4cbc19e97db7d35e62360cc4adb34c6f562df1e5 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dmc.c
+++ b/drivers/gpu/drm/i915/display/intel_dmc.c
@@ -600,6 +600,12 @@ 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);
@@ -607,6 +613,9 @@ 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));