Hi Laurent,
I like the approach, current practice when almost every bridge should
optionally implement connector, or alternatively downstream bridge or
panel is very painful.
More comments inlined.
On 07.07.2019 20:18, Laurent Pinchart wrote:
> To support implementation of DRM connectors on top of DRM bridges
> instead of by bridges, the drm_bridge needs to expose new operations and
> data:
>
> - Output detection, hot-plug notification, mode retrieval and EDID
> retrieval operations
> - Bitmask of supported operations
Why do we need these bitmask at all? Why cannot we rely on presence of
operation's callback?
> - Bridge output type
>
> Add and document these.
>
> Three new bridge helper functions are also added to handle hot plug
> notification in a way that is as transparent as possible for the
> bridges.
Documentation of new opses does not explain how it should cooperate with
bridge chaining, I suppose they should be chained explicitly, am I
right? More comments about it later.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_bridge.c | 92 +++++++++++++++++++
> include/drm/drm_bridge.h | 170 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 261 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 519577f363e3..3c2a255df7af 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -70,6 +70,8 @@ static LIST_HEAD(bridge_list);
> */
> void drm_bridge_add(struct drm_bridge *bridge)
> {
> + mutex_init(&bridge->hpd_mutex);
> +
> mutex_lock(&bridge_lock);
> list_add_tail(&bridge->list, &bridge_list);
> mutex_unlock(&bridge_lock);
> @@ -86,6 +88,8 @@ void drm_bridge_remove(struct drm_bridge *bridge)
> mutex_lock(&bridge_lock);
> list_del_init(&bridge->list);
> mutex_unlock(&bridge_lock);
> +
> + mutex_destroy(&bridge->hpd_mutex);
> }
> EXPORT_SYMBOL(drm_bridge_remove);
>
> @@ -463,6 +467,94 @@ void drm_atomic_bridge_enable(struct drm_bridge *bridge,
> }
> EXPORT_SYMBOL(drm_atomic_bridge_enable);
>
> +/**
> + * drm_bridge_hpd_enable - enable hot plug detection for the bridge
> + * @bridge: bridge control structure
> + * @cb: hot-plug detection callback
> + * @data: data to be passed to the hot-plug detection callback
> + *
> + * Call &drm_bridge_funcs.hpd_enable and register the given @cb and @data as
> + * hot plug notification callback. From now on the @cb will be called with
> + * @data when an output status change is detected by the bridge, until hot plug
> + * notification gets disabled with drm_bridge_hpd_disable().
> + *
> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> + * bridge->ops. This function shall not be called when the flag is not set.
> + *
> + * Only one hot plug detection callback can be registered at a time, it is an
> + * error to call this function when hot plug detection is already enabled for
> + * the bridge.
> + */
To simplify architecture maybe would be better to enable hpd just on
bridge attach:
bridge->hpd_cb = cb;
bridge->hpd_data = data;
ret = drm_bridge_attach(...);
This way we could avoid adding new callbacks hpd_(enable|disable)
without big sacrifices.
One more thing: HPD in DisplayPort/HDMI beside signalling plug/unplug,
notifies about sink status change, how it translates to this cb?
> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> + void (*cb)(void *data,
> + enum drm_connector_status status),
> + void *data)
> +{
> + if (!bridge || !bridge->funcs->hpd_enable)
> + return;
> +
> + mutex_lock(&bridge->hpd_mutex);
> +
> + if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
> + goto unlock;
> +
> + bridge->hpd_cb = cb;
> + bridge->hpd_data = data;
> +
> + bridge->funcs->hpd_enable(bridge);
> +
> +unlock:
> + mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);
> +
> +/**
> + * drm_bridge_hpd_disable - disable hot plug detection for the bridge
> + * @bridge: bridge control structure
> + *
> + * Call &drm_bridge_funcs.hpd_disable and unregister the hot plug detection
> + * callback previously registered with drm_bridge_hpd_enable(). Once this
> + * function returns the callback will not be called by the bridge when an
> + * output status change occurs.
> + *
> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> + * bridge->ops. This function shall not be called when the flag is not set.
> + */
> +void drm_bridge_hpd_disable(struct drm_bridge *bridge)
> +{
> + if (!bridge || !bridge->funcs->hpd_disable)
> + return;
> +
> + mutex_lock(&bridge->hpd_mutex);
> + bridge->funcs->hpd_disable(bridge);
> +
> + bridge->hpd_cb = NULL;
> + bridge->hpd_data = NULL;
> + mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
> +
> +/**
> + * drm_bridge_hpd_notify - notify hot plug detection events
> + * @bridge: bridge control structure
> + * @status: output connection status
> + *
> + * Bridge drivers shall call this function to report hot plug events when they
> + * detect a change in the output status, when hot plug detection has been
> + * enabled by the &drm_bridge_funcs.hpd_enable callback.
> + *
> + * This function shall be called in a context that can sleep.
> + */
> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> + enum drm_connector_status status)
> +{
> + mutex_lock(&bridge->hpd_mutex);
> + if (bridge->hpd_cb)
> + bridge->hpd_cb(bridge->hpd_data, status);
> + mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
> +
> #ifdef CONFIG_OF
> /**
> * of_drm_find_bridge - find the bridge corresponding to the device node in
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 08dc15f93ded..b9445aa5b1ef 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -23,8 +23,9 @@
> #ifndef __DRM_BRIDGE_H__
> #define __DRM_BRIDGE_H__
>
> -#include <linux/list.h>
> #include <linux/ctype.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> #include <drm/drm_mode_object.h>
> #include <drm/drm_modes.h>
>
> @@ -334,6 +335,110 @@ struct drm_bridge_funcs {
> */
> void (*atomic_post_disable)(struct drm_bridge *bridge,
> struct drm_atomic_state *state);
> +
> + /**
> + * @detect:
> + *
> + * Check if anything is attached to the bridge output.
> + *
> + * This callback is optional, if not implemented the bridge will be
> + * considered as always having a component attached to its output.
> + * Bridges that implement this callback shall set the
> + * DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
> + *
> + * RETURNS:
> + *
> + * drm_connector_status indicating the bridge output status.
> + */
> + enum drm_connector_status (*detect)(struct drm_bridge *bridge);
> +
> + /**
> + * @get_modes:
> + *
> + * Fill all modes currently valid for the sink into the &drm_connector
> + * with drm_mode_probed_add().
> + *
> + * The @get_modes callback is mostly intended to support non-probable
> + * displays such as many fixed panels. Bridges that support reading
> + * EDID shall leave @get_modes unimplemented and implement the
> + * &drm_bridge_funcs->get_edid callback instead.
> + *
> + * This callback is optional. Bridges that implement it shall set the
> + * DRM_BRIDGE_OP_MODES flag in their &drm_bridge->ops.
> + *
> + * RETURNS:
> + *
> + * The number of modes added by calling drm_mode_probed_add().
> + */
> + int (*get_modes)(struct drm_bridge *bridge,
> + struct drm_connector *connector);
> +
> + /**
> + * @get_edid:
> + *
> + * Read and parse the EDID data of the connected display.
> + *
> + * The @get_edid callback is the preferred way of reporting mode
> + * information for a display connected to the bridge output. Bridges
> + * that support readind EDID shall implement this callback and leave
> + * the @get_modes callback unimplemented.
> + *
> + * The caller of this operation shall first verify the output
> + * connection status and refrain from reading EDID from a disconnected
> + * output.
> + *
> + * This callback is optional. Bridges that implement it shall set the
> + * DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
> + *
> + * RETURNS:
> + *
> + * An edid structure newly allocated with kmalloc() (or similar) on
> + * success, or NULL otherwise. The caller is responsible for freeing
> + * the returned edid structure with kfree().
> + */
> + struct edid *(*get_edid)(struct drm_bridge *bridge,
> + struct drm_connector *connector);
It overlaps with get_modes, I guess presence of one ops should disallow
presence of another one?
I am not really convinced we need this op at all, cannot we just assign
some helper function to .get_modes cb, which will do the same?
Regards
Andrzej
> +
> + /**
> + * @lost_hotplug:
> + *
> + * Notify the bridge of display disconnection.
> + *
> + * This callback is optional, it may be implemented by bridges that
> + * need to be notified of display disconnection for internal reasons.
> + * One use case is to reset the internal state of CEC controllers for
> + * HDMI bridges.
> + */
> + void (*lost_hotplug)(struct drm_bridge *bridge);
> +
> + /**
> + * @hpd_enable:
> + *
> + * Enable hot plug detection. From now on the bridge shall call
> + * drm_bridge_hpd_notify() each time a change is detected in the output
> + * connection status, until hot plug detection gets disabled with
> + * @hpd_disable.
> + *
> + * This callback is optional and shall only be implemented by bridges
> + * that support hot-plug notification without polling. Bridges that
> + * implement it shall also implement the @hpd_disable callback and set
> + * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> + */
> + void (*hpd_enable)(struct drm_bridge *bridge);
> +
> + /**
> + * @hpd_disable:
> + *
> + * Disable hot plug detection. Once this function returns the bridge
> + * shall not call drm_bridge_hpd_notify() when a change in the output
> + * connection status occurs.
> + *
> + * This callback is optional and shall only be implemented by bridges
> + * that support hot-plug notification without polling. Bridges that
> + * implement it shall also implement the @hpd_enable callback and set
> + * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> + */
> + void (*hpd_disable)(struct drm_bridge *bridge);
> };
>
> /**
> @@ -372,6 +477,38 @@ struct drm_bridge_timings {
> bool dual_link;
> };
>
> +/**
> + * enum drm_bridge_ops - Bitmask of operations supported by the bridge
> + */
> +enum drm_bridge_ops {
> + /**
> + * @DRM_BRIDGE_OP_DETECT: The bridge can detect displays connected to
> + * its output. Bridges that set this flag shall implement the
> + * &drm_bridge_funcs->detect callback.
> + */
> + DRM_BRIDGE_OP_DETECT = BIT(0),
> + /**
> + * @DRM_BRIDGE_OP_EDID: The bridge can retrieve the EDID of the display
> + * connected to its output. Bridges that set this flag shall implement
> + * the &drm_bridge_funcs->get_edid callback.
> + */
> + DRM_BRIDGE_OP_EDID = BIT(1),
> + /**
> + * @DRM_BRIDGE_OP_HPD: The bridge can detect hot-plug and hot-unplug
> + * without requiring polling. Bridges that set this flag shall
> + * implement the &drm_bridge_funcs->hpd_enable and
> + * &drm_bridge_funcs->disable_hpd_cb callbacks.
> + */
> + DRM_BRIDGE_OP_HPD = BIT(2),
> + /**
> + * @DRM_BRIDGE_OP_MODES: The bridge can retrieving the modes supported
> + * by the display at its output. This does not include readind EDID
> + * which is separately covered by @DRM_BRIDGE_OP_EDID. Bridges that set
> + * this flag shall implement the &drm_bridge_funcs->get_modes callback.
> + */
> + DRM_BRIDGE_OP_MODES = BIT(3),
> +};
> +
> /**
> * struct drm_bridge - central DRM bridge control structure
> */
> @@ -398,6 +535,29 @@ struct drm_bridge {
> const struct drm_bridge_funcs *funcs;
> /** @driver_private: pointer to the bridge driver's internal context */
> void *driver_private;
> + /** @ops: bitmask of operations supported by the bridge */
> + enum drm_bridge_ops ops;
> + /**
> + * @type: Type of the connection at the bridge output
> + * (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this
> + * identifies the type of connected display.
> + */
> + int type;
> + /** private: */
> + /**
> + * @hpd_mutex: Protects the @hpd_cb and @hpd_data fields.
> + */
> + struct mutex hpd_mutex;
> + /**
> + * @hpd_cb: Hot plug detection callback, registered with
> + * drm_bridge_hpd_enable().
> + */
> + void (*hpd_cb)(void *data, enum drm_connector_status status);
> + /**
> + * @hpd_data: Private data passed to the Hot plug detection callback
> + * @hpd_cb.
> + */
> + void *hpd_data;
> };
>
> void drm_bridge_add(struct drm_bridge *bridge);
> @@ -428,6 +588,14 @@ void drm_atomic_bridge_pre_enable(struct drm_bridge *bridge,
> void drm_atomic_bridge_enable(struct drm_bridge *bridge,
> struct drm_atomic_state *state);
>
> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> + void (*cb)(void *data,
> + enum drm_connector_status status),
> + void *data);
> +void drm_bridge_hpd_disable(struct drm_bridge *bridge);
> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> + enum drm_connector_status status);
> +
> #ifdef CONFIG_DRM_PANEL_BRIDGE
> struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
> u32 connector_type);
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