linux-kernel - [PATCH 09/29] drm/modeset: Create atomic

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Message-Id: <20250902-drm-state-readout-v1-9-14ad5315da3f@kernel.org>
Date: Tue, 02 Sep 2025 10:32:37 +0200
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>, 
 Jyri Sarha <jyri.sarha@....fi>, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Devarsh Thakkar <devarsht@...com>, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, Maxime Ripard <mripard@...nel.org>
Subject: [PATCH 09/29] drm/modeset: Create atomic_reset hook

Since we're about to integrate some infrastructure to implement hardware
state readout, we need a way to differentiate between drivers wanting to
start from a pristine state, with the classic reset sequence, and
drivers that want to pickup their initial state from reading out the
hardware state.

To do so we can create an optional reset hook in
drm_mode_config_helper_funcs that will default to the classic reset
implementation, and can be setup to a helper we will provide in a later
patch to read the hardware state.

Signed-off-by: Maxime Ripard <mripard@...nel.org>
---
 drivers/gpu/drm/drm_mode_config.c        | 32 +++++++++++++++++++++++---------
 include/drm/drm_modeset_helper_vtables.h | 13 +++++++++++++
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 25f376869b3a41d47bbe72b0df3e35cad142f3e6..82180760032d3490d63fe83136465d2c26551d08 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -27,10 +27,11 @@
 #include <drm/drm_encoder.h>
 #include <drm/drm_file.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_mode_config.h>
+#include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_print.h>
 #include <linux/dma-resv.h>
 
 #include "drm_crtc_internal.h"
 #include "drm_internal.h"
@@ -179,19 +180,11 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
 	drm_connector_list_iter_end(&conn_iter);
 
 	return ret;
 }
 
-/**
- * drm_mode_config_reset - call ->reset callbacks
- * @dev: drm device
- *
- * This functions calls all the crtc's, encoder's and connector's ->reset
- * callback. Drivers can use this in e.g. their driver load or resume code to
- * reset hardware and software state.
- */
-void drm_mode_config_reset(struct drm_device *dev)
+static void drm_mode_config_reset_pristine(struct drm_device *dev)
 {
 	struct drm_crtc *crtc;
 	struct drm_plane *plane;
 	struct drm_encoder *encoder;
 	struct drm_connector *connector;
@@ -213,10 +206,31 @@ void drm_mode_config_reset(struct drm_device *dev)
 	drm_for_each_connector_iter(connector, &conn_iter)
 		if (connector->funcs->reset)
 			connector->funcs->reset(connector);
 	drm_connector_list_iter_end(&conn_iter);
 }
+
+/**
+ * drm_mode_config_reset - call ->reset callbacks
+ * @dev: drm device
+ *
+ * This functions calls all the crtc's, encoder's and connector's ->reset
+ * callback. Drivers can use this in e.g. their driver load or resume code to
+ * reset hardware and software state.
+ */
+void drm_mode_config_reset(struct drm_device *dev)
+{
+	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
+		const struct drm_mode_config_helper_funcs *funcs =
+			dev->mode_config.helper_private;
+
+		if (funcs && funcs->atomic_reset)
+			return funcs->atomic_reset(dev);
+	}
+
+	return drm_mode_config_reset_pristine(dev);
+}
 EXPORT_SYMBOL(drm_mode_config_reset);
 
 /*
  * Global properties
  */
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index ce7c7aeac887bb8438d73710f16071c97a851839..6d22a7676d6bf49fb78af4d0706bd91005cef186 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -1561,8 +1561,21 @@ struct drm_mode_config_helper_funcs {
 	 * how one should implement this.
 	 *
 	 * This hook is optional.
 	 */
 	int (*atomic_commit_setup)(struct drm_atomic_state *state);
+
+	/**
+	 * @atomic_reset:
+	 *
+	 * This hook is used to create the initial @drm_atomic_state.
+	 * It's used by drm_mode_config_reset().
+	 *
+	 * The default implementation will create an empty one, but
+	 * drivers can provide an alternative implementation to, for
+	 * example, read the initial state from hardware to implement
+	 * flicker-free and / or faster boot.
+	 */
+	void (*atomic_reset)(struct drm_device *dev);
 };
 
 #endif

-- 
2.50.1