drm/probe_helper: Add drm_connector_helper_funcs.mode_valid_ctx

This is just an atomic version of mode_valid, which is intended to be
used for situations where a driver might need to check the atomic state
of objects other than the connector itself. One such example is with
MST, where the maximum possible bandwidth on a connector can change
dynamically irregardless of the display configuration.

Changes since v1:
* Use new drm logging functions
* Make some corrections in the mode_valid_ctx kdoc
* Return error codes or 0 from ->mode_valid_ctx() on fail, and store the
  drm_mode_status in an additional function parameter
Changes since v2:
* Don't accidentally assign ret to mode->status on success, or we'll
  squash legitimate mode validation results
* Don't forget to assign MODE_OK to status in drm_connector_mode_valid()
  if we have no callbacks
* Drop leftover hunk in drm_modes.h around enum drm_mode_status
Changes since v3:
* s/return ret/return 0/ in drm_mode_validate_pipeline()
* Minor cleanup in drm_connector_mode_valid()

Tested-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200713170746.254388-2-lyude@redhat.com

diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h b/drivers/gpu/drm/drm_crtc_helper_internal.h
index f0a66ef..25ce42e 100644 (file)
--- a/drivers/gpu/drm/drm_crtc_helper_internal.h
+++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
@@ -73,8 +73,11 @@ enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
                                         const struct drm_display_mode *mode);
 enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
                                            const struct drm_display_mode *mode);
-enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
-                                             struct drm_display_mode *mode);
+int
+drm_connector_mode_valid(struct drm_connector *connector,
+                        struct drm_display_mode *mode,
+                        struct drm_modeset_acquire_ctx *ctx,
+                        enum drm_mode_status *status);
 
 struct drm_encoder *
 drm_connector_get_single_encoder(struct drm_connector *connector);

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 26e997f..601a4f2 100644 (file)
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -86,17 +86,19 @@ drm_mode_validate_flag(const struct drm_display_mode *mode,
        return MODE_OK;
 }
 
-static enum drm_mode_status
+static int
 drm_mode_validate_pipeline(struct drm_display_mode *mode,
-                           struct drm_connector *connector)
+                          struct drm_connector *connector,
+                          struct drm_modeset_acquire_ctx *ctx,
+                          enum drm_mode_status *status)
 {
        struct drm_device *dev = connector->dev;
-       enum drm_mode_status ret = MODE_OK;
        struct drm_encoder *encoder;
+       int ret;
 
        /* Step 1: Validate against connector */
-       ret = drm_connector_mode_valid(connector, mode);
-       if (ret != MODE_OK)
+       ret = drm_connector_mode_valid(connector, mode, ctx, status);
+       if (ret || *status != MODE_OK)
                return ret;
 
        /* Step 2: Validate against encoders and crtcs */
@@ -104,8 +106,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
                struct drm_bridge *bridge;
                struct drm_crtc *crtc;
 
-               ret = drm_encoder_mode_valid(encoder, mode);
-               if (ret != MODE_OK) {
+               *status = drm_encoder_mode_valid(encoder, mode);
+               if (*status != MODE_OK) {
                        /* No point in continuing for crtc check as this encoder
                         * will not accept the mode anyway. If all encoders
                         * reject the mode then, at exit, ret will not be
@@ -114,8 +116,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
                }
 
                bridge = drm_bridge_chain_get_first_bridge(encoder);
-               ret = drm_bridge_chain_mode_valid(bridge, mode);
-               if (ret != MODE_OK) {
+               *status = drm_bridge_chain_mode_valid(bridge, mode);
+               if (*status != MODE_OK) {
                        /* There is also no point in continuing for crtc check
                         * here. */
                        continue;
@@ -125,17 +127,17 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
                        if (!drm_encoder_crtc_ok(encoder, crtc))
                                continue;
 
-                       ret = drm_crtc_mode_valid(crtc, mode);
-                       if (ret == MODE_OK) {
+                       *status = drm_crtc_mode_valid(crtc, mode);
+                       if (*status == MODE_OK) {
                                /* If we get to this point there is at least
                                 * one combination of encoder+crtc that works
                                 * for this mode. Lets return now. */
-                               return ret;
+                               return 0;
                        }
                }
        }
 
-       return ret;
+       return 0;
 }
 
 static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
@@ -196,16 +198,27 @@ enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
        return encoder_funcs->mode_valid(encoder, mode);
 }
 
-enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
-                                             struct drm_display_mode *mode)
+int
+drm_connector_mode_valid(struct drm_connector *connector,
+                        struct drm_display_mode *mode,
+                        struct drm_modeset_acquire_ctx *ctx,
+                        enum drm_mode_status *status)
 {
        const struct drm_connector_helper_funcs *connector_funcs =
                connector->helper_private;
+       int ret = 0;
+
+       if (!connector_funcs)
+               *status = MODE_OK;
+       else if (connector_funcs->mode_valid_ctx)
+               ret = connector_funcs->mode_valid_ctx(connector, mode, ctx,
+                                                     status);
+       else if (connector_funcs->mode_valid)
+               *status = connector_funcs->mode_valid(connector, mode);
+       else
+               *status = MODE_OK;
 
-       if (!connector_funcs || !connector_funcs->mode_valid)
-               return MODE_OK;
-
-       return connector_funcs->mode_valid(connector, mode);
+       return ret;
 }
 
 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
@@ -375,8 +388,9 @@ EXPORT_SYMBOL(drm_helper_probe_detect);
  *      (if specified)
  *    - drm_mode_validate_flag() checks the modes against basic connector
  *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
- *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
- *      driver and/or sink specific checks
+ *    - the optional &drm_connector_helper_funcs.mode_valid or
+ *      &drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver
+ *      and/or sink specific checks
  *    - the optional &drm_crtc_helper_funcs.mode_valid,
  *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
  *      helpers can perform driver and/or source specific checks which are also
@@ -507,22 +521,39 @@ retry:
                mode_flags |= DRM_MODE_FLAG_3D_MASK;
 
        list_for_each_entry(mode, &connector->modes, head) {
-               if (mode->status == MODE_OK)
-                       mode->status = drm_mode_validate_driver(dev, mode);
+               if (mode->status != MODE_OK)
+                       continue;
+
+               mode->status = drm_mode_validate_driver(dev, mode);
+               if (mode->status != MODE_OK)
+                       continue;
 
-               if (mode->status == MODE_OK)
-                       mode->status = drm_mode_validate_size(mode, maxX, maxY);
+               mode->status = drm_mode_validate_size(mode, maxX, maxY);
+               if (mode->status != MODE_OK)
+                       continue;
 
-               if (mode->status == MODE_OK)
-                       mode->status = drm_mode_validate_flag(mode, mode_flags);
+               mode->status = drm_mode_validate_flag(mode, mode_flags);
+               if (mode->status != MODE_OK)
+                       continue;
 
-               if (mode->status == MODE_OK)
-                       mode->status = drm_mode_validate_pipeline(mode,
-                                                                 connector);
+               ret = drm_mode_validate_pipeline(mode, connector, &ctx,
+                                                &mode->status);
+               if (ret) {
+                       drm_dbg_kms(dev,
+                                   "drm_mode_validate_pipeline failed: %d\n",
+                                   ret);
+
+                       if (drm_WARN_ON_ONCE(dev, ret != -EDEADLK)) {
+                               mode->status = MODE_ERROR;
+                       } else {
+                               drm_modeset_backoff(&ctx);
+                               goto retry;
+                       }
+               }
 
-               if (mode->status == MODE_OK)
-                       mode->status = drm_mode_validate_ycbcr420(mode,
-                                                                 connector);
+               if (mode->status != MODE_OK)
+                       continue;
+               mode->status = drm_mode_validate_ycbcr420(mode, connector);
        }
 
 prune:

diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 421a30f..4efec30 100644 (file)
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -968,6 +968,48 @@ struct drm_connector_helper_funcs {
         */
        enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
                                           struct drm_display_mode *mode);
+
+       /**
+        * @mode_valid_ctx:
+        *
+        * Callback to validate a mode for a connector, irrespective of the
+        * specific display configuration.
+        *
+        * This callback is used by the probe helpers to filter the mode list
+        * (which is usually derived from the EDID data block from the sink).
+        * See e.g. drm_helper_probe_single_connector_modes().
+        *
+        * This function is optional, and is the atomic version of
+        * &drm_connector_helper_funcs.mode_valid.
+        *
+        * To allow for accessing the atomic state of modesetting objects, the
+        * helper libraries always call this with ctx set to a valid context,
+        * and &drm_mode_config.connection_mutex will always be locked with
+        * the ctx parameter set to @ctx. This allows for taking additional
+        * locks as required.
+        *
+        * Even though additional locks may be acquired, this callback is
+        * still expected not to take any constraints into account which would
+        * be influenced by the currently set display state - such constraints
+        * should be handled in the driver's atomic check. For example, if a
+        * connector shares display bandwidth with other connectors then it
+        * would be ok to validate the minimum bandwidth requirement of a mode
+        * against the maximum possible bandwidth of the connector. But it
+        * wouldn't be ok to take the current bandwidth usage of other
+        * connectors into account, as this would change depending on the
+        * display state.
+        *
+        * Returns:
+        * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
+        * the &enum drm_mode_status value to @status, or a negative error
+        * code otherwise.
+        *
+        */
+       int (*mode_valid_ctx)(struct drm_connector *connector,
+                             struct drm_display_mode *mode,
+                             struct drm_modeset_acquire_ctx *ctx,
+                             enum drm_mode_status *status);
+
        /**
         * @best_encoder:
         *