In order to enable drivers to read their initial state from the
hardware, each KMS object needs a hook to fill a pre-allocated state
from the hardware registers.

Introduce the atomic_sro_readout_state hook in every KMS object funcs
vtable: drm_crtc_funcs, drm_plane_funcs, drm_connector_funcs,
drm_bridge_funcs, and drm_private_state_funcs.

Also introduce the drm_mode_config_funcs.atomic_sro_readout_state and
drm_mode_config_helper_funcs.atomic_sro_build_state hooks, which are the
top-level entry points for drivers and helpers respectively.

Finally, add drm_atomic_sro_can_readout() to verify that all objects on
a device implement the readout hook, and wire it into
drm_atomic_sro_device_can_readout().

Signed-off-by: Maxime Ripard <[email protected]>
---
 drivers/gpu/drm/drm_atomic_sro.c         | 59 ++++++++++++++++++++++++++++++++
 include/drm/drm_atomic.h                 | 25 ++++++++++++++
 include/drm/drm_bridge.h                 | 31 +++++++++++++++++
 include/drm/drm_connector.h              | 26 ++++++++++++++
 include/drm/drm_crtc.h                   | 26 ++++++++++++++
 include/drm/drm_mode_config.h            | 18 ++++++++++
 include/drm/drm_modeset_helper_vtables.h | 23 +++++++++++++
 include/drm/drm_plane.h                  | 26 ++++++++++++++
 8 files changed, 234 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_sro.c b/drivers/gpu/drm/drm_atomic_sro.c
index 28beba4de0ce..f90f7cda182b 100644
--- a/drivers/gpu/drm/drm_atomic_sro.c
+++ b/drivers/gpu/drm/drm_atomic_sro.c
@@ -4,10 +4,11 @@
 #include <drm/drm_atomic_sro.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_plane.h>
 #include <drm/drm_print.h>
 #include <linux/module.h>
 
 #include "drm_internal.h"
@@ -23,10 +24,62 @@ enum drm_atomic_readout_status {
 static unsigned int atomic_readout = DRM_ATOMIC_READOUT_ENABLED;
 module_param_unsafe(atomic_readout, uint, 0400);
 MODULE_PARM_DESC(atomic_readout,
                 "Enable Hardware State Readout (0 = disabled, 1 = enabled, 2 = 
ignore missing compares, 3 = ignore missing readouts and compares, default = 
1)");
 
+static bool drm_atomic_sro_can_readout(struct drm_device *dev)
+{
+       struct drm_crtc *crtc;
+       struct drm_plane *plane;
+       struct drm_connector *connector;
+       struct drm_private_obj *privobj;
+       struct drm_connector_list_iter conn_iter;
+
+       if (atomic_readout == DRM_ATOMIC_READOUT_SKIP_MISSING_READOUT)
+               return true;
+
+       if (!dev->mode_config.funcs->atomic_sro_readout_state)
+               return false;
+
+       drm_for_each_privobj(privobj, dev) {
+               if (!privobj->funcs->atomic_sro_readout_state) {
+                       drm_dbg_atomic(dev,
+                                      "Private object %s missing readout 
callback",
+                                      privobj->name);
+                       return false;
+               }
+       }
+
+       drm_for_each_plane(plane, dev) {
+               if (!plane->funcs->atomic_sro_readout_state) {
+                       drm_dbg_atomic(dev, "Plane %s missing readout callback",
+                                      plane->name);
+                       return false;
+               }
+       }
+
+       drm_for_each_crtc(crtc, dev) {
+               if (!crtc->funcs->atomic_sro_readout_state) {
+                       drm_dbg_atomic(dev, "CRTC %s missing readout callback",
+                                      crtc->name);
+                       return false;
+               }
+       }
+
+       drm_connector_list_iter_begin(dev, &conn_iter);
+       drm_for_each_connector_iter(connector, &conn_iter) {
+               if (!connector->funcs->atomic_sro_readout_state) {
+                       drm_dbg_atomic(dev, "Connector %s missing readout 
callback",
+                                      connector->name);
+                       return false;
+               }
+       }
+       drm_connector_list_iter_end(&conn_iter);
+
+       return true;
+}
+
 /**
  * drm_atomic_sro_device_can_readout - check if a device supports hardware 
state readout
  * @dev: DRM device to check
  *
  * Verifies that the device is an atomic driver, that readout is
@@ -37,16 +90,22 @@ MODULE_PARM_DESC(atomic_readout,
  * True if the device supports full hardware state readout, false
  * otherwise.
  */
 bool drm_atomic_sro_device_can_readout(struct drm_device *dev)
 {
+       bool ret;
+
        if (!drm_drv_uses_atomic_modeset(dev))
                return false;
 
        if (atomic_readout == DRM_ATOMIC_READOUT_DISABLED)
                return false;
 
+       ret = drm_atomic_sro_can_readout(dev);
+       if (!ret)
+               return false;
+
        return true;
 }
 EXPORT_SYMBOL(drm_atomic_sro_device_can_readout);
 
 struct __drm_atomic_sro_plane {
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 47b2fe2b039e..657f5f4c223f 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -296,10 +296,35 @@ struct drm_private_state_funcs {
         * Frees the private object state created with @atomic_duplicate_state.
         */
        void (*atomic_destroy_state)(struct drm_private_obj *obj,
                                     struct drm_private_state *state);
 
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * Initializes @obj_state to reflect the current hardware state
+        * of the private object.
+        *
+        * It is meant to be used by drivers that want to implement
+        * flicker-free boot (also called fastboot by i915) and allows
+        * to initialize the atomic state from the hardware state left
+        * by the firmware.
+        *
+        * It is used at initialization time, so drivers must make sure
+        * that the power state is sensible when accessing the hardware.
+        *
+        * This hook is mandatory for drivers implementing SRO, but can
+        * be left unassigned otherwise.
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+       int (*atomic_sro_readout_state)(struct drm_private_obj *obj,
+                                       struct drm_atomic_sro_state *state,
+                                       struct drm_private_state *obj_state);
+
        /**
         * @atomic_print_state:
         *
         * If driver subclasses &struct drm_private_state, it should implement
         * this optional hook for printing additional driver specific state.
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index d14c50460e94..9f15c9087e58 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -373,10 +373,41 @@ struct drm_bridge_funcs {
         * The @atomic_post_disable callback is optional.
         */
        void (*atomic_post_disable)(struct drm_bridge *bridge,
                                    struct drm_atomic_commit *state);
 
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * Initializes @bridge_state to reflect the current hardware
+        * state of the bridge.
+        *
+        * It is meant to be used by drivers that want to implement
+        * flicker-free boot (also called fastboot by i915) and allows
+        * to initialize the atomic state from the hardware state left
+        * by the firmware.
+        *
+        * It is used at initialization time, so drivers must make sure
+        * that the power state is sensible when accessing the hardware.
+        *
+        * The @crtc_state and @conn_state parameters point to the CRTC
+        * and connector states for the pipeline this bridge is part
+        * of.
+        *
+        * This hook is mandatory for drivers implementing SRO, but can
+        * be left unassigned otherwise.
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+       int (*atomic_sro_readout_state)(struct drm_bridge *bridge,
+                                       struct drm_atomic_sro_state *state,
+                                       struct drm_bridge_state *bridge_state,
+                                       struct drm_crtc_state *crtc_state,
+                                       struct drm_connector_state *conn_state);
+
        /**
         * @atomic_duplicate_state:
         *
         * Duplicate the current bridge state object (which is guaranteed to be
         * non-NULL).
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 4317166562cf..7e2fda565f63 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -32,10 +32,11 @@
 #include <drm/drm_util.h>
 #include <drm/drm_property.h>
 
 #include <uapi/drm/drm_mode.h>
 
+struct drm_atomic_sro_state;
 struct drm_connector_helper_funcs;
 struct drm_modeset_acquire_ctx;
 struct drm_device;
 struct drm_crtc;
 struct drm_display_mode;
@@ -1660,10 +1661,35 @@ struct drm_connector_funcs {
         * A new, pristine, connector state instance or an error pointer
         * on failure.
         */
        struct drm_connector_state *(*atomic_create_state)(struct drm_connector 
*connector);
 
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * Initializes @conn_state to reflect the current hardware
+        * state of the connector.
+        *
+        * It is meant to be used by drivers that want to implement
+        * flicker-free boot (also called fastboot by i915) and allows
+        * to initialize the atomic state from the hardware state left
+        * by the firmware.
+        *
+        * It is used at initialization time, so drivers must make sure
+        * that the power state is sensible when accessing the hardware.
+        *
+        * This hook is mandatory for drivers implementing SRO, but can
+        * be left unassigned otherwise.
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+       int (*atomic_sro_readout_state)(struct drm_connector *connector,
+                                       struct drm_atomic_sro_state *state,
+                                       struct drm_connector_state *conn_state);
+
        /**
         * @atomic_duplicate_state:
         *
         * Duplicate the current atomic state for this connector and return it.
         * The core and helpers guarantee that any atomic state duplicated with
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 152349f973e3..fde0e5f87665 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -33,10 +33,11 @@
 #include <drm/drm_device.h>
 #include <drm/drm_plane.h>
 #include <drm/drm_debugfs_crc.h>
 #include <drm/drm_mode_config.h>
 
+struct drm_atomic_sro_state;
 struct drm_connector;
 struct drm_device;
 struct drm_framebuffer;
 struct drm_mode_set;
 struct drm_file;
@@ -652,10 +653,35 @@ struct drm_crtc_funcs {
         * A new, pristine, CRTC state instance or an error pointer
         * on failure.
         */
        struct drm_crtc_state *(*atomic_create_state)(struct drm_crtc *crtc);
 
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * Initializes @crtc_state to reflect the current hardware
+        * state of the CRTC.
+        *
+        * It is meant to be used by drivers that want to implement
+        * flicker-free boot (also called fastboot by i915) and allows
+        * to initialize the atomic state from the hardware state left
+        * by the firmware.
+        *
+        * It is used at initialization time, so drivers must make sure
+        * that the power state is sensible when accessing the hardware.
+        *
+        * This hook is mandatory for drivers implementing SRO, but can
+        * be left unassigned otherwise.
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+       int (*atomic_sro_readout_state)(struct drm_crtc *crtc,
+                                       struct drm_atomic_sro_state *state,
+                                       struct drm_crtc_state *crtc_state);
+
        /**
         * @atomic_duplicate_state:
         *
         * Duplicate the current atomic state for this CRTC and return it.
         * The core and helpers guarantee that any atomic state duplicated with
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index d8f5b7e9673e..14eab7b126ea 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -319,10 +319,28 @@ struct drm_mode_config_funcs {
         *
         * Subclassing of &drm_atomic_commit is deprecated in favour of using
         * &drm_private_state and &drm_private_obj.
         */
        void (*atomic_state_free)(struct drm_atomic_commit *state);
+
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * This optional hook is called at initialization time to read
+        * out the hardware state and initialize the DRM objects' atomic
+        * states from it.
+        *
+        * When implemented, the framework will prefer hardware state
+        * readout over creating pristine default states, enabling the
+        * first modeset to be skipped if the firmware already set up
+        * the display (flicker-free boot).
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+        int (*atomic_sro_readout_state)(struct drm_device *dev);
 };
 
 /**
  * struct drm_mode_config - Mode configuration control structure
  * @min_width: minimum fb pixel width on this device
diff --git a/include/drm/drm_modeset_helper_vtables.h 
b/include/drm/drm_modeset_helper_vtables.h
index ca6268945c28..697d90c9e66d 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -1550,8 +1550,31 @@ struct drm_mode_config_helper_funcs {
         * how one should implement this.
         *
         * This hook is optional.
         */
        int (*atomic_commit_setup)(struct drm_atomic_commit *state);
+
+       /**
+        * @atomic_sro_build_state:
+        *
+        * Builds a &struct drm_atomic_sro_state from the current
+        * hardware state by calling the atomic_sro_readout_state hooks
+        * on every KMS object.
+        *
+        * This hook is called both at initialization time, to create
+        * the initial state from what the firmware programmed, and
+        * after blocking commits, to read back the hardware state and
+        * compare it to what was committed.
+        *
+        * The default implementation is
+        * drm_atomic_helper_sro_build_state().
+        *
+        * RETURNS:
+        *
+        * A &struct drm_atomic_sro_state on success, an error pointer
+        * otherwise.
+        */
+       struct drm_atomic_sro_state *
+       (*atomic_sro_build_state)(struct drm_device *dev);
 };
 
 #endif
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 2c5a5a70a71b..d841fee3a9cd 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -30,10 +30,11 @@
 #include <drm/drm_color_mgmt.h>
 #include <drm/drm_rect.h>
 #include <drm/drm_modeset_lock.h>
 #include <drm/drm_util.h>
 
+struct drm_atomic_sro_state;
 struct drm_crtc;
 struct drm_plane_size_hint;
 struct drm_printer;
 struct drm_modeset_acquire_ctx;
 
@@ -402,10 +403,35 @@ struct drm_plane_funcs {
         * A new, pristine, plane state instance or an error pointer
         * on failure.
         */
        struct drm_plane_state *(*atomic_create_state)(struct drm_plane *plane);
 
+       /**
+        * @atomic_sro_readout_state:
+        *
+        * Initializes @plane_state to reflect the current hardware
+        * state of the plane.
+        *
+        * It is meant to be used by drivers that want to implement
+        * flicker-free boot (also called fastboot by i915) and allows
+        * to initialize the atomic state from the hardware state left
+        * by the firmware.
+        *
+        * It is used at initialization time, so drivers must make sure
+        * that the power state is sensible when accessing the hardware.
+        *
+        * This hook is mandatory for drivers implementing SRO, but can
+        * be left unassigned otherwise.
+        *
+        * RETURNS:
+        *
+        * 0 on success, a negative error code otherwise.
+        */
+       int (*atomic_sro_readout_state)(struct drm_plane *plane,
+                                       struct drm_atomic_sro_state *state,
+                                       struct drm_plane_state *plane_state);
+
        /**
         * @atomic_duplicate_state:
         *
         * Duplicate the current atomic state for this plane and return it.
         * The core and helpers guarantee that any atomic state duplicated with

-- 
2.54.0

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