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

Imre Deak
2020-07-07T22:40:45Z

Sorry for the delay, the review as I promised:

On Tue, May 26, 2020 at 02:23:09PM -0400, Lyude Paul wrote:
> 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
^mode against?

Reviewed-by: Imre Deak <imre.deak@intel.com>

> + * 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
>
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