drm/vc4: kms: Improve logging

When debugging, finding out what muxing decisions were made and what the
actual core clock rate is is always useful, so let's add some more
messages.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20220328153659.2382206-7-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_kms.c

@@ -439,6 +439,9 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
 		 * requirements.
 		 */
 		clk_set_min_rate(hvs->core_clk, new_hvs_state->core_clock_rate);
+
+		drm_dbg(dev, "Core clock actual rate: %lu Hz\n",
+			clk_get_rate(hvs->core_clk));
 	}
 }
 
@@ -822,9 +825,18 @@ static int vc4_pv_muxing_atomic_check(struct drm_device *dev,
 		unsigned int matching_channels;
 		unsigned int channel;
 
+		drm_dbg(dev, "%s: Trying to find a channel.\n", crtc->name);
+
 		/* Nothing to do here, let's skip it */
-		if (old_crtc_state->enable == new_crtc_state->enable)
+		if (old_crtc_state->enable == new_crtc_state->enable) {
+			if (new_crtc_state->enable)
+				drm_dbg(dev, "%s: Already enabled, reusing channel %d.\n",
+					crtc->name, new_vc4_crtc_state->assigned_channel);
+			else
+				drm_dbg(dev, "%s: Disabled, ignoring.\n", crtc->name);
+
 			continue;
+		}
 
 		/* Muxing will need to be modified, mark it as such */
 		new_vc4_crtc_state->update_muxing = true;
@@ -832,6 +844,10 @@ static int vc4_pv_muxing_atomic_check(struct drm_device *dev,
 		/* If we're disabling our CRTC, we put back our channel */
 		if (!new_crtc_state->enable) {
 			channel = old_vc4_crtc_state->assigned_channel;
+
+			drm_dbg(dev, "%s: Disabling, Freeing channel %d\n",
+				crtc->name, channel);
+
 			hvs_new_state->fifo_state[channel].in_use = false;
 			new_vc4_crtc_state->assigned_channel = VC4_HVS_CHANNEL_DISABLED;
 			continue;
@@ -866,6 +882,8 @@ static int vc4_pv_muxing_atomic_check(struct drm_device *dev,
 			return -EINVAL;
 
 		channel = ffs(matching_channels) - 1;
+
+		drm_dbg(dev, "Assigned HVS channel %d to CRTC %s\n", channel, crtc->name);
 		new_vc4_crtc_state->assigned_channel = channel;
 		unassigned_channels &= ~BIT(channel);
 		hvs_new_state->fifo_state[channel].in_use = true;