On Sat, Feb 22, 2020 at 4:01 PM Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> 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
> - Bridge output type
> - I2C adapter for DDC access
>
> 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.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Tested-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> ---
> Changes since v6:
>
> - Don't check for NULL bridge in drm_bridge_hpd_enable() and
> drm_bridge_hpd_disable()
>
> Changes since v3:
>
> - Fix typos
>
> Changes since v2:
>
> - Add wrappers around the .detect(), .get_modes() and .get_edid()
> operations
> - Warn bridge drivers about valid usage of the connector argument to
> .get_modes() and .get_edid()
>
> Changes since v1:
>
> - Make .hpd_enable() and .hpd_disable() optional
> - Rename .lost_hotplug() to .hpd_notify()
> - Add ddc field to drm_bridge
> ---
> drivers/gpu/drm/drm_bridge.c | 201 ++++++++++++++++++++++++++++++++++-
> include/drm/drm_bridge.h | 192 ++++++++++++++++++++++++++++++++-
> 2 files changed, 391 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 5f55a9e17a7c..d236984a963e 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -82,6 +82,8 @@ 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);
> @@ -98,6 +100,8 @@ 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);
>
> @@ -228,7 +232,7 @@ void drm_bridge_detach(struct drm_bridge *bridge)
> * Bridge drivers expose operations through the &drm_bridge_funcs structure.
> * The DRM internals (atomic and CRTC helpers) use the helpers defined in
> * drm_bridge.c to call bridge operations. Those operations are divided in
> - * two big categories to support different parts of the bridge usage.
> + * three big categories to support different parts of the bridge usage.
> *
> * - The encoder-related operations support control of the bridges in the
> * chain, and are roughly counterparts to the &drm_encoder_helper_funcs
> @@ -258,6 +262,43 @@ void drm_bridge_detach(struct drm_bridge *bridge)
> * implement them shall thus also implement the atomic version of the
> * encoder-related operations. This feature is not supported by the legacy
> * CRTC helpers.
> + *
> + * - The connector-related operations support implementing a &drm_connector
> + * based on a chain of bridges. DRM bridges traditionally create a
> + * &drm_connector for bridges meant to be used at the end of the chain. This
> + * puts additional burden on bridge drivers, especially for bridges that may
> + * be used in the middle of a chain or at the end of it. Furthermore, it
> + * requires all operations of the &drm_connector to be handled by a single
> + * bridge, which doesn't always match the hardware architecture.
> + *
> + * To simplify bridge drivers and make the connector implementation more
> + * flexible, a new model allows bridges to unconditionally skip creation of
> + * &drm_connector and instead expose &drm_bridge_funcs operations to support
> + * an externally-implemented &drm_connector. Those operations are
> + * &drm_bridge_funcs.detect, &drm_bridge_funcs.get_modes,
> + * &drm_bridge_funcs.get_edid, &drm_bridge_funcs.hpd_notify,
> + * &drm_bridge_funcs.hpd_enable and &drm_bridge_funcs.hpd_disable. When
> + * implemented, display drivers shall create a &drm_connector instance for
> + * each chain of bridges, and implement those connector instances based on
> + * the bridge connector operations.
> + *
> + * Bridge drivers shall implement the connector-related operations for all
> + * the features that the bridge hardware support. For instance, if a bridge
> + * supports reading EDID, the &drm_bridge_funcs.get_edid shall be
> + * implemented. This however doesn't mean that the DDC lines are wired to the
> + * bridge on a particular platform, as they could also be connected to an I2C
> + * controller of the SoC. Support for the connector-related operations on the
> + * running platform is reported through the &drm_bridge.ops flags. Bridge
> + * drivers shall detect which operations they can support on the platform
> + * (usually this information is provided by ACPI or DT), and set the
> + * &drm_bridge.ops flags for all supported operations. A flag shall only be
> + * set if the corresponding &drm_bridge_funcs operation is implemented, but
> + * an implemented operation doesn't necessarily imply that the corresponding
> + * flag will be set. Display drivers shall use the &drm_bridge.ops flags to
> + * decide which bridge to delegate a connector operation to. This mechanism
> + * allows providing a single static const &drm_bridge_funcs instance in
> + * bridge drivers, improving security by storing function pointers in
> + * read-only memory.
Good enough that even dense me gets this now!
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> */
>
> /**
> @@ -957,6 +998,164 @@ int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
> }
> EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
>
> +/**
> + * drm_bridge_detect - check if anything is attached to the bridge output
> + * @bridge: bridge control structure
> + *
> + * If the bridge supports output detection, as reported by the
> + * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect for the
> + * bridge and return the connection status. Otherwise return
> + * connector_status_unknown.
> + *
> + * RETURNS:
> + * The detection status on success, or connector_status_unknown if the bridge
> + * doesn't support output detection.
> + */
> +enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge)
> +{
> + if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
> + return connector_status_unknown;
> +
> + return bridge->funcs->detect(bridge);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_detect);
> +
> +/**
> + * drm_bridge_get_modes - fill all modes currently valid for the sink into the
> + * @connector
> + * @bridge: bridge control structure
> + * @connector: the connector to fill with modes
> + *
> + * If the bridge supports output modes retrieval, as reported by the
> + * DRM_BRIDGE_OP_MODES bridge ops flag, call &drm_bridge_funcs.get_modes to
> + * fill the connector with all valid modes and return the number of modes
> + * added. Otherwise return 0.
> + *
> + * RETURNS:
> + * The number of modes added to the connector.
> + */
> +int drm_bridge_get_modes(struct drm_bridge *bridge,
> + struct drm_connector *connector)
> +{
> + if (!(bridge->ops & DRM_BRIDGE_OP_MODES))
> + return 0;
> +
> + return bridge->funcs->get_modes(bridge, connector);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
> +
> +/**
> + * drm_bridge_get_edid - get the EDID data of the connected display
> + * @bridge: bridge control structure
> + * @connector: the connector to read EDID for
> + *
> + * If the bridge supports output EDID retrieval, as reported by the
> + * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
> + * get the EDID and return it. Otherwise return ERR_PTR(-ENOTSUPP).
> + *
> + * RETURNS:
> + * The retrieved EDID on success, or an error pointer otherwise.
> + */
> +struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
> + struct drm_connector *connector)
> +{
> + if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
> + return ERR_PTR(-ENOTSUPP);
> +
> + return bridge->funcs->get_edid(bridge, connector);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_get_edid);
> +
> +/**
> + * 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 if implemented 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.
> + */
> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> + void (*cb)(void *data,
> + enum drm_connector_status status),
> + void *data)
> +{
> + if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
> + 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;
> +
> + if (bridge->funcs->hpd_enable)
> + 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 if implemented 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->ops & DRM_BRIDGE_OP_HPD))
> + return;
> +
> + mutex_lock(&bridge->hpd_mutex);
> + if (bridge->funcs->hpd_disable)
> + 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 drm_bridge_hpd_enable().
> + *
> + * 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 38de129d5947..9d5d750973e9 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_atomic.h>
> #include <drm/drm_encoder.h>
> @@ -33,7 +34,10 @@
>
> struct drm_bridge;
> struct drm_bridge_timings;
> +struct drm_connector;
> struct drm_panel;
> +struct edid;
> +struct i2c_adapter;
>
> /**
> * struct drm_bridge_funcs - drm_bridge control functions
> @@ -497,6 +501,119 @@ struct drm_bridge_funcs {
> * giving the reason of the failure otherwise.
> */
> struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
> +
> + /**
> + * @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-probeable
> + * 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.
> + *
> + * The connector parameter shall be used for the sole purpose of
> + * filling modes, and shall not be stored internally by bridge drivers
> + * for future usage.
> + *
> + * 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 reading 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.
> + *
> + * The connector parameter shall be used for the sole purpose of EDID
> + * retrieval and parsing, and shall not be stored internally by bridge
> + * drivers for future usage.
> + *
> + * 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);
> +
> + /**
> + * @hpd_notify:
> + *
> + * Notify the bridge of hot plug detection.
> + *
> + * This callback is optional, it may be implemented by bridges that
> + * need to be notified of display connection or disconnection for
> + * internal reasons. One use case is to reset the internal state of CEC
> + * controllers for HDMI bridges.
> + */
> + void (*hpd_notify)(struct drm_bridge *bridge,
> + enum drm_connector_status status);
> +
> + /**
> + * @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);
> };
>
> /**
> @@ -535,6 +652,39 @@ 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->hpd_disable callbacks if they support enabling
> + * and disabling hot-plug detection dynamically.
> + */
> + DRM_BRIDGE_OP_HPD = BIT(2),
> + /**
> + * @DRM_BRIDGE_OP_MODES: The bridge can retrieve the modes supported
> + * by the display at its output. This does not include reading 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
> */
> @@ -563,6 +713,33 @@ 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;
> + /**
> + * @ddc: Associated I2C adapter for DDC access, if any.
> + */
> + struct i2c_adapter *ddc;
> + /** 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;
> };
>
> static inline struct drm_bridge *
> @@ -669,6 +846,19 @@ drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
> u32 output_fmt,
> unsigned int *num_input_fmts);
>
> +enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge);
> +int drm_bridge_get_modes(struct drm_bridge *bridge,
> + struct drm_connector *connector);
> +struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
> + struct drm_connector *connector);
> +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);
> struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
> --
> Regards,
>
> Laurent Pinchart
>
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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