drm/vc4: Add logging and comments

The HVS core clock isn't really obvious, so let's add a bunch more
comments and some logging for easier debugging.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20220225143534.405820-12-maxime@cerno.tech

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index bffd81d..4d01697 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -390,8 +390,15 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
                                                500000000,
                                                new_hvs_state->core_clock_rate);
 
+               drm_dbg(dev, "Raising the core clock at %lu Hz\n", core_rate);
+
+               /*
+                * Do a temporary request on the core clock during the
+                * modeset.
+                */
                clk_set_min_rate(hvs->core_clk, core_rate);
        }
+
        drm_atomic_helper_commit_modeset_disables(dev, state);
 
        vc4_ctm_commit(vc4, state);
@@ -417,6 +424,10 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
                drm_dbg(dev, "Running the core clock at %lu Hz\n",
                        new_hvs_state->core_clock_rate);
 
+               /*
+                * Request a clock rate based on the current HVS
+                * requirements.
+                */
                clk_set_min_rate(hvs->core_clk, new_hvs_state->core_clock_rate);
        }
 }