drm: apple: Trigger set_digital_out_mode when minRR is changed

DCP requires a "mode change" to be triggered when changing the minRR
property of the IOMFBParameter_adaptive_sync parameter set. Additionally,
the setting of the parameter set must be fenced by a wait cookie, or DCP
will crash.

We cannot trigger a "full" modeset with iomfb_modeset as that function
has failure conditions. iomfb_flush must never fail. iomfb_modeset also
has a very large timeout.

Luckily for us, toggling VRR on and off does not actually trigger a full
modeset on the connected sink when calling set_digital_out_mode. It is
therefore safe to set the parameter and trigger set_digital_out_mode
directly from iomfb_flush. If this for some reason times out, just
fire a vblank and return gracefully.

Signed-off-by: James Calligeros <[email protected]>

Author: chadmed

drivers/gpu/drm/apple/dcp-internal.h

@@ -186,6 +186,8 @@ struct apple_dcp {
 	bool during_modeset;
 	bool valid_mode;
 	bool use_timestamps;
+	bool vrr_enabled;
+	s64 min_vrr;
 	struct dcp_set_digital_out_mode_req mode;
 
 	/* completion for active turning true */

drivers/gpu/drm/apple/iomfb_template.c

@@ -1251,6 +1251,11 @@ int DCP_FW_NAME(iomfb_modeset)(struct apple_dcp *dcp,
 	/* Keep track of suspected vrr modes */
 	dcp->use_timestamps = mode->vrr;
 
+	if (mode->vrr)
+		dcp->min_vrr = mode->min_vrr;
+	else
+		dcp->min_vrr = 0;
+
 	cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
 	if (!cookie) {
 		return -ENOMEM;
@@ -1263,11 +1268,8 @@ int DCP_FW_NAME(iomfb_modeset)(struct apple_dcp *dcp,
 
 	dcp->during_modeset = true;
 
-	if (mode->vrr)
-		dcp_set_adaptive_sync(dcp, mode->min_vrr, cookie);
-	else
-		dcp_set_digital_out_mode(dcp, false, &dcp->mode,
-					 complete_set_digital_out_mode, cookie);
+	dcp_set_digital_out_mode(dcp, false, &dcp->mode,
+				 complete_set_digital_out_mode, cookie);
 
 	/*
 	 * The DCP firmware has an internal timeout of ~8 seconds for
@@ -1434,6 +1436,39 @@ void DCP_FW_NAME(iomfb_flush)(struct apple_dcp *dcp, struct drm_crtc *crtc, stru
 		dcp->brightness.update = false;
 	}
 
+	/*
+	 * If VRR is requested, we need to set the minRR parameter
+	 * and then call set_digital_out_mode. This does *not* trigger
+	 * a full modeset.
+	 */
+	if (crtc_state->vrr_enabled != dcp->vrr_enabled) {
+		struct dcp_wait_cookie *cookie;
+		int timeout;
+
+		cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
+		if (!cookie) {
+			schedule_work(&dcp->vblank_wq);
+			return;
+		}
+
+		init_completion(&cookie->done);
+		kref_init(&cookie->refcount);
+		kref_get(&cookie->refcount);
+
+		dcp_set_adaptive_sync(dcp, crtc_state->vrr_enabled ? dcp->min_vrr : 0, cookie);
+
+		timeout = wait_for_completion_timeout(&cookie->done,
+						      msecs_to_jiffies(500));
+		if (!timeout) {
+			schedule_work(&dcp->vblank_wq);
+			return;
+		}
+
+		kref_put(&cookie->refcount, release_wait_cookie);
+
+		dcp->vrr_enabled = crtc_state->vrr_enabled;
+	}
+
 	if (crtc_state->color_mgmt_changed) {
 		struct iomfb_set_matrix_req mat = {
 			.location = 9,