[PATCH 1/2] drm/probe_helper: Add drm_connector_helper_funcs.mode_valid_ctx

Lyude Paul
2020-05-26T18:23:30Z

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.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Tested-by: Lee Shawn C <shawn.c.lee@intel.com>
---
drivers/gpu/drm/drm_crtc_helper_internal.h | 6 +-
drivers/gpu/drm/drm_probe_helper.c | 65 ++++++++++++++--------
include/drm/drm_modeset_helper_vtables.h | 41 ++++++++++++++
3 files changed, 88 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h b/drivers/gpu/drm/drm_crtc_helper_internal.h
index f0a66ef47e5ad..ca767cba6094d 100644
--- a/drivers/gpu/drm/drm_crtc_helper_internal.h
+++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
@@ -73,8 +73,10 @@ 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);
+enum drm_mode_status
+drm_connector_mode_valid(struct drm_connector *connector,
+ struct drm_display_mode *mode,
+ struct drm_modeset_acquire_ctx *ctx);

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 466dfbba82564..3132784736841 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -86,16 +86,17 @@ 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)
{
struct drm_device *dev = connector->dev;
- enum drm_mode_status ret = MODE_OK;
struct drm_encoder *encoder;
+ int ret = MODE_OK;

/* Step 1: Validate against connector */
- ret = drm_connector_mode_valid(connector, mode);
+ ret = drm_connector_mode_valid(connector, mode, ctx);
if (ret != MODE_OK)
return ret;

@@ -196,16 +197,23 @@ 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)
{
const struct drm_connector_helper_funcs *connector_funcs =
connector->helper_private;

- if (!connector_funcs || !connector_funcs->mode_valid)
+ if (!connector_funcs)
return MODE_OK;

- return connector_funcs->mode_valid(connector, mode);
+ if (connector_funcs->mode_valid_ctx)
+ return connector_funcs->mode_valid_ctx(connector, mode, ctx);
+ else if (connector_funcs->mode_valid)
+ return connector_funcs->mode_valid(connector, mode);
+ else
+ return MODE_OK;
}

#define DRM_OUTPUT_POLL_PERIOD (10*HZ)
@@ -375,8 +383,9 @@ 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 +516,34 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
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);
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ } else if (WARN_ON_ONCE(ret < 0)) {
+ mode->status = MODE_BAD;
+ } else {
+ mode->status = ret;
+ }

- 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 421a30f084631..8f020c3424b2b 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -968,6 +968,47 @@ 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_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 a mode uses 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:
+ *
+ * Either &drm_mode_status.MODE_OK, one of the failure reasons in
+ * &enum drm_mode_status, or -EDEADLK if a deadlock would have
+ * occurred and we need to backoff.
+ *
+ */
+ int (*mode_valid_ctx)(struct drm_connector *connector,
+ struct drm_display_mode *mode,
+ struct drm_modeset_acquire_ctx *ctx);
+
/**
* @best_encoder:
*
--
2.26.2