linux-kernel - [PATCH v5 08/16] drm/bridge: Add helper to reset bridge pipeline

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Message-Id: <20250304-bridge-connector-v5-8-aacf461d2157@kernel.org>
Date: Tue, 04 Mar 2025 12:10:51 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
 Simona Vetter <simona@...ll.ch>, Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Douglas Anderson <dianders@...omium.org>
Cc: Herve Codina <herve.codina@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona.vetter@...ll.ch>
Subject: [PATCH v5 08/16] drm/bridge: Add helper to reset bridge pipeline

Let's provide an helper to make it easier for bridge drivers to
power-cycle their bridge.

In order to avoid a circular dependency between that new helper and
drm_atomic_helper_reset_crtc(), this new helper will be in a
drm_bridge_helper.c file to follow the pattern we have for other
objects.

Co-developed-by: Simona Vetter <simona.vetter@...ll.ch>
Signed-off-by: Maxime Ripard <mripard@...nel.org>
---
 drivers/gpu/drm/Makefile            |  1 +
 drivers/gpu/drm/drm_bridge_helper.c | 55 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_bridge_helper.h     | 12 ++++++++
 3 files changed, 68 insertions(+)

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 4cd054188faf0b3dec442efd99ae52604541bce1..5a332f7d3ecccb6e5e1fb9fb811eab7aa5a84a21 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -131,10 +131,11 @@ obj-$(CONFIG_DRM_TTM_HELPER) += drm_ttm_helper.o
 #
 
 drm_kms_helper-y := \
 	drm_atomic_helper.o \
 	drm_atomic_state_helper.o \
+	drm_bridge_helper.o \
 	drm_crtc_helper.o \
 	drm_damage_helper.o \
 	drm_flip_work.o \
 	drm_format_helper.o \
 	drm_gem_atomic_helper.o \
diff --git a/drivers/gpu/drm/drm_bridge_helper.c b/drivers/gpu/drm/drm_bridge_helper.c
new file mode 100644
index 0000000000000000000000000000000000000000..521df9d5dcb3fef842a95cdb2865a8b8d09b0fbe
--- /dev/null
+++ b/drivers/gpu/drm/drm_bridge_helper.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_bridge_helper.h>
+#include <drm/drm_modeset_lock.h>
+
+/**
+ * drm_bridge_helper_reset_crtc - Reset the pipeline feeding a bridge
+ * @bridge: DRM bridge to reset
+ * @ctx: lock acquisition context
+ *
+ * Reset a @bridge pipeline. It will power-cycle all active components
+ * between the CRTC and connector that bridge is connected to.
+ *
+ * Returns:
+ *
+ * 0 on success or a negative error code on failure. If the error
+ * returned is EDEADLK, the whole atomic sequence must be restarted.
+ */
+int drm_bridge_helper_reset_crtc(struct drm_bridge *bridge,
+				 struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_connector *connector;
+	struct drm_encoder *encoder = bridge->encoder;
+	struct drm_device *dev = encoder->dev;
+	struct drm_crtc *crtc;
+	int ret;
+
+	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
+	if (ret)
+		return ret;
+
+	connector = drm_atomic_get_connector_for_encoder(encoder, ctx);
+	if (IS_ERR(connector)) {
+		ret = PTR_ERR(connector);
+		goto out;
+	}
+
+	if (!connector->state) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	crtc = connector->state->crtc;
+	ret = drm_atomic_helper_reset_crtc(crtc, ctx);
+	if (ret)
+		goto out;
+
+out:
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(drm_bridge_helper_reset_crtc);
diff --git a/include/drm/drm_bridge_helper.h b/include/drm/drm_bridge_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..6c35b479ec2a84aa43283351a6f18e49a9f9c177
--- /dev/null
+++ b/include/drm/drm_bridge_helper.h
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#ifndef __DRM_BRIDGE_HELPER_H_
+#define __DRM_BRIDGE_HELPER_H_
+
+struct drm_bridge;
+struct drm_modeset_acquire_ctx;
+
+int drm_bridge_helper_reset_crtc(struct drm_bridge *bridge,
+				 struct drm_modeset_acquire_ctx *ctx);
+
+#endif // __DRM_BRIDGE_HELPER_H_

-- 
2.48.1