[PATCH 09/60] drm/bridge: Add connector-related bridge operations and data
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Sat Aug 10 22:43:13 UTC 2019
Hi Andrzej,
On Fri, Aug 09, 2019 at 01:55:53PM +0200, Andrzej Hajda wrote:
> On 08.08.2019 21:32, Laurent Pinchart wrote:
> > On Tue, Jul 16, 2019 at 03:57:21PM +0200, Andrzej Hajda wrote:
> >> On 16.07.2019 11:00, Daniel Vetter wrote:
> >>> On Fri, Jul 12, 2019 at 11:01:38AM +0200, Andrzej Hajda wrote:
> >>>> On 11.07.2019 17:50, Daniel Vetter wrote:
> >>>>> On Thu, Jul 11, 2019 at 05:12:26PM +0200, Andrzej Hajda wrote:
> >>>>>> On 11.07.2019 15:18, Daniel Vetter wrote:
> >>>>>>> On Thu, Jul 11, 2019 at 02:41:01PM +0200, Andrzej Hajda wrote:
> >>>>>>>> On 11.07.2019 09:35, Daniel Vetter wrote:
> >>>>>>>>> On Wed, Jul 10, 2019 at 02:12:14PM +0200, Andrzej Hajda wrote:
> >>>>>>>>>> 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.
> >>>>>>>>>
> >>>>>>>>> Yeah I think this looks mostly reasonable. Some api design comments on top
> >>>>>>>>> of Andrzej', with the fair warning that I didn't bother to read up on how
> >>>>>>>>> it's all used in the end. I probably should go and do that, at least to
> >>>>>>>>> get a feeling for what your hpd_cb usually does.
> >>>>>>>>>
> >>>>>>>>>> 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?
> >>>>>>>>>
> >>>>>>>>> Yeah also not a huge fan of these bitmasks. Smells like
> >>>>>>>>>
> >>>>>>>>> DRIVER_GEM|DRIVER_MODESET, and I personally really hate those. Easy to
> >>>>>>>>> add, generally good excuse to not have to think through the design between
> >>>>>>>>> different parts of drivers - "just" add another flag.
> >>>>>>>>>
> >>>>>>>>>>> - 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 at ideasonboard.com>
> >>>>>>>>>>> ---
> >>>>>>>>>>> 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(...);
> >>>>>>>>>
> >>>>>>>>> Yeah I like this more. The other problem here is, what if you need more
> >>>>>>>>> than 1 callback registers on the same bridge hdp signal?
> >>>>>>>>>
> >>>>>>>>>> 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);
> >>>>>>>>>
> >>>>>>>>> So this isn't quite what I had in mind. Instead something like this:
> >>>>>>>>>
> >>>>>>>>> /* iterates over all bridges in the chain containing @bridge */
> >>>>>>>>> for_each_bridge(tmp_bridge, bridge) {
> >>>>>>>>> if (tmp_bridge == bridge)
> >>>>>>>>> continue;
> >>>>>>>>> if (bridge->hpd_notify);
> >>>>>>>>> bridge->hpd_notify(tmp_bridge, bridge, status);
> >>>>>>>>> }
> >>>>>>>>>
> >>>>>>>>> encoder = encoder_for_bridge(bridge);
> >>>>>>>>> if (encoder->helper_private->bridge_hpd_notify)
> >>>>>>>>> encoder->helper_private->bridge_hpd_notify(encoder, bridge, status);
> >>>>>>>>>
> >>>>>>>>> dev = bridge->dev
> >>>>>>>>> if (dev->mode_config.helper_private->bridge_hpd_notify)
> >>>>>>>>> dev->mode_config.helper_private->bridge_hpd_notify(dev, bridge, status)
> >>>>>>>>>
> >>>>>>>>> No register callback needed, no locking needed, everyone gets exactly the
> >>>>>>>>> hpd they want/need.
> >>>>>>>>
> >>>>>>>> As I understand you want to notify every member of the pipeline.
> >>>>>>>>
> >>>>>>>> I think it should be enough to notify only the source, and then source
> >>>>>>>> should decide if/when the hpd should be propagated upstream.
> >>>>>>>>
> >>>>>>>> It looks more generic for me.
> >>>>>>>
> >>>>>>> I'm not parsing ... do you think my idea is more generic and useful, or
> >>>>>>> the one from Laurent? Kinda confused here.
> >>>>>>
> >>>>>> Regarding general idea:
> >>>>>>
> >>>>>> 1. Laurent's approach is to notify only consumer, I guess usually video
> >>>>>> source.
> >>>>>>
> >>>>>> 2. Your is to notify all other bridges and encoder.
> >>>>>>
> >>>>>> And I prefer 1st approach, why:
> >>>>>>
> >>>>>> - the source can decide if/when and to who propagate the signal,
> >>>>>>
> >>>>>> - is more generic, for example if bridge send signal to two
> >>>>>> monitors/panels, it can delay hpd propagation till both sinks are present,
> >>>>>
> >>>>> With Laurent's approach the bridge cannot send the hpd to more than one
> >>>>> consumer. There's only 1 callback. So you're example doesn't work.
> >>>>
> >>>> If there will be two consumers, there will be two bridge attachments,
> >>>> thus there will be two notifications, it should work.
> >>>
> >>> 2 consumers, 1 producer. There's only _one_ callback in the producer. The
> >>> callback is registered on the produce bridge, not on the consumer bridge
> >>> (or I'm totallly misreading what Laurent does here).
> >>
> >> I have assumed that if devices exposes two hardware sink interfaces it
> >> will expose two separate bridges - of course it will not work with
> >> "bridge chaining" thing, but this is a different story.
> >
> > Daniel is right that the current implementation only allows one
> > consumer. This is however not a limitation of the API, but of its
> > implementation, as I only needed a single consumer. The helpers in this
> > series ensure that neither the consumer nor the producer poke in the
> > drm_bridge structure to call back to the HPD handler:
> >
> > - The consumer calls drm_bridge_hpd_enable() and
> > drm_bridge_hpd_disable(), which could offer a reference-counted
> > behaviour if desired without changes to the consumer.
> >
> > - The producer gets configured by .hpd_enable() and .hpd_disable(),
> > which could also easily accommodate reference-counting in the drm
> > bridge core without changes to the producer.
> >
> > - The producer notifies HPD with drm_bridge_hpd_notify(), which could
> > easily be extended to support multiple consumers without changes to
> > the producer.
> >
> > This is actually my second version of the HPD mechanism. The first
> > version was never posted, poked into drm_bridge, and required the
> > producer to be aware of the callbacks. After discussing this privately
> > with Daniel, I came up with the implementation in this series that,
> > while not supporting multiple consumers now, makes it easy to extend
> > later without minimal effort.
> >
> > Daniel's proposed implementation above looks reasonable to me, provided
> > we can iterate over the bridges in an order that don't depend on the
> > position of the producer in the chain (should be easy to solve by
> > starting at the encoder for instance). It however looks a bit like a
> > midlayer to me :-) That's why I have a similar implementation in the
> > connector-bridge helper, which could be extended to call
> > encoder->helper_private->bridge_hpd_notify() and
> > dev->mode_config.helper_private->bridge_hpd_notify() instead of
> > hardcoding drm_kms_helper_hotplug_event(). Moving the code to
> > drm_bridge_hpd_notify() would on the other hand set the notification
> > sequence towards the encoder and driver in stone. Daniel, do you think
> > that would be better ?
> >
> > I would like to remind everybody that this series isn't the last I will
> > ever submit, and I plan to do more work on drm_bridge and drm_panel. I'm
> > open to suggestions, and can address problems on top of these patches,
> > provided obviously that this series doesn't go in the wrong direction.
> > I'm of course also willing to rework this series, but given the amount
> > of work we have in the drm_bridge realm, I can't fix everything in one
> > go :-)
> >
> >>>>>> - it resembles hardware wires :)
> >>>>>
> >>>>> This isn't for the hw wires afaiui. The hw hpd terminates in the source
> >>>>> bridge, which then calls drm_bridge_hpd_notify() to inform anyone else
> >>>>> interested in that hpd singal. This includes:
> >>>>> - Other bridges, e.g. if they provide CEC support.
> >>>>> - Other bridges, maybe they need to re-run the HDCP state engine
> >>>>> - Overall driver, so it can update the modes/connector status and send the
> >>>>> uevent to the driver.
> >>>>> - Overall display pipeline for this specific bridge, maybe you need to
> >>>>> shut down/re-enable the pipe because $reasons.
> >>>>>
> >>>>> That's at least my understanding from lots of chats with Laurent about
> >>>>> what he wants to do here.
> >
> > That's correct, and that's what I was trying to implement :-) The
> > notification, in this patch series, goes from the producer bridge to a
> > central place (namely the connector, with a helper implementation
> > available as part of this series, but custom implementations in display
> > drivers are fine if needed) that then dispatches the notification to all
> > bridges (through the .lost_hotplug() operation, which we could replace
> > by an .hpd_notify() operation) for the first two purposes listed above,
> > and then to the overall driver. The only thing I don't support yet is
> > dispatching to the display pipeline (item 4 in the list above) as I had
> > no need for that, and didn't want to develop an API with no user. This
> > would however not be difficult to do when needed, the need is taken into
> > account in the proposed implementation.
> >
> >>>> I do not know the full picture, but the solution where particular bridge
> >>>> notifies everything unconditionally seems to me much less flexible.
> >>>>
> >>>> If HPD signals is received by the consumer, if there are no obstacles it
> >>>> can propagate it further, upstream bridge/encoder or to drm core - it
> >>>> will mimic your scenario.
> >>>>
> >>>> But there are also other scenarios where bridge does not want to
> >>>> propagate signal, because for example:
> >>>>
> >>>> - it wants to wait for other sinks to wake up,
> >>>>
> >>> The other sink can just do that in their hpd callback.
> >>>
> >>>> - it propagates HPD signal via hardware wire,
> >>> Again, the other sink can just not listen to sw hpd in that case, and use
> >>> the wire/hw hpd interrupt.
> >>>
> >> If it should ignore HPD, why it should receive it at all - it is
> >> unnecessary noise. And I am afraid with more complicated pipelines it
> >> will be impossible for particular component (bridge/encoder/whatever) to
> >> distinguish if HPD notification which came from non-directly connected
> >> component should be ignored or not.
> >>
> >>>> - first it wants to verify if the sink is valid/compatible/authorized
> >>>> device.
> >>>
> >>> Now you lost me. Why would someone glue incompatible IP into a SoC or
> >>> board?
> >>
> >> Bridge can have external connectors, and the user can connect there
> >> anything.
> >>
> >>>> In general HPD is input signal for notify of state changes on particular
> >>>> bus, in case of typical video bridge on its output video bus.
> >>>>
> >>>> In case of bridges they have also input video buses, and they can send
> >>>> HPD signal via this bus, but this is indeed different HPD signal, even
> >>>> if for most cases they looks similar.
> >>>
> >>> Ah, I think this is a problem we will eventually have. But it's not
> >>> something we're currently solving here at all I think.
> >>
> >> Currently sii8620 device in tm2 sends hpd signal upstream via hardware
> >> line, so this is not something from far future. And I guess with HPD
> >> broadcasting it could be racy/error prone, for example EDID reading can
> >> fail due to bridge being not ready (ddc of sii8620 is connected to i2c
> >> controller via hw wires also).
> >>
> >>>>>> And regarding implementation:
> >>>>>>
> >>>>>> 1. Laurent proposes to register callback drm_bridge_hpd_enable.
> >>>>>>
> >>>>>> 2. You propose to add ops hpd_notify in bridges and encoders.
> >>>>>>
> >>>>>> Your proposition is more straightforward, but if we want to notify only
> >>>>>> source we should locate it by parsing notification chain (what about
> >>>>>> unchained bridges), or store pointer somewhere during attachment.
> >>>>>>
> >>>>>> It still leaves us with this ugly dualism - source is encoder or bridge,
> >>>>>> similarly to sink as bridge or panel, but fixing it can be done later.
> >>>>>
> >>>>> Uh I think we're not talking about the same thing really. My understanding
> >>>>> is that this callback is if someone (outside of this bridge) is interested
> >>>>> in a hpd signal _from_ this bridge. Which means you can only ever have 1
> >>>>> listener.
> >>>>
> >>>> Do we have real life examples?
> >>>>
> >>>> I want to distinguish two situations:
> >>>>
> >>>> - another device wants to know if input bus of the bridge has changed state,
> >>>>
> >>>> - another device wants to know if output bus of the bridge has changed
> >>>> state.
> >>>
> >>> Uh, that's what drm_bridge_state is for (if it ever happens). That's how
> >>> bridges can exchange state and information about each another. hpd is
> >>> about the physical world, i.e. "is there a cable plugged into the port
> >>> I'm driving?". We're not going to use fake hpd to update bridge state and
> >>> fun stuff like that, we have the atomic_check machinery for this.
> >>
> >> My question was if we have real examples that upstream device requires
> >> knowledge about state of output line of the bridge?
> >>
> >> To be more precise, we have following display pipeline:
> >>
> >> A-->B-->C
> >>
> >> And C sends HPD to B (ie signal that state of line between B and C
> >> changed). Does A really wants to know this information? or it should
> >> just need to know if state of line A-->B changed?
> >
> > There's one real life example, where A is an HDMI encoder, B is an HDMI
> > ESD protector and level shifter, and C is the physical HDMI connector.
> > When the HDMI cable is unplugged, the CEC controller part of A needs to
> > be notified in order to reset the CEC state machine. One could however
> > argue that in that case the A-B link state changes too, but the
> > important part is that HPD detection is not performed by A, while A
> > needs to be informed of lost hotplug.
>
> I have no full picture but I guess in this case C sends HPD to B using
> hardware wire, and then B sends HPD to A also via wire, so I wouldn't
> say that B does not participate in HPD transmission/forwarding,
No, in this case A doesn't receive any hardware HPD signal, it requires
HPD notification through software.
> some shifters with 'advanced power saving' can even perform wake-up of
> upstream pin logic after receiving HPD on downstream, so HPD sent from B
> to A is indeed different than HPD sent from C to B.
>
> Btw, with the above logic of propagation of HPD callback (proposed by
> Daniel) I guess it will work this way:
>
> - A will receive HPD signal via HW,
>
> - then B and C will receive HPD callback via framework.
>
> Am I right?
It's the other way around.
In this case the HPD signal from the connector (C) is routed to an input
of the ESD chip (B). The ESD chip outputs a shifted HPD hardware signal
connected to a GPIO of the SoC. The driver for (B) thus registers a GPIO
IRQ and receive the hardware HPD notification. The driver for the HDMI
encoder (A) needs to receive HPD notification in software, through the
framework.
> >>>>> You seem to have some other idea here.
> >>>>>
> >>>>>>>>>>> + 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?
> >>>>>>>>>
> >>>>>>>>> Plan B): ditch ->get_edid, require that the driver has ->get_modes in that
> >>>>>>>>> case, and require that if it has an edid it must fill out connector->info
> >>>>>>>>> and connector->edid correctly.
> >>>>>>>>>
> >>>>>>>>> Btw if a hpd happens, who's responible for making sure the edid/mode list
> >>>>>>>>> in the connector is up-to-date? With your current callback design that's
> >>>>>>>>> up to the callback, which doesn't feel great. Maybe drm_bridge_hpd_notify
> >>>>>>>>> should guarantee that it'll first walk the connectors to update status and
> >>>>>>>>> edid/mode list for the final drm_connector. And then instead of just
> >>>>>>>>> passing the simple "status", it'll pass the connector, with everything
> >>>>>>>>> correctly updated.
> >>>>>>>>>
> >>>>>>>>> Otherwise everyone interested in that hpd signal will go and re-fetch the
> >>>>>>>>> edid, which is not so awesome :-)
> >>>>>>>>>
> >>>>>>>>>>> +
> >>>>>>>>>>> + /**
> >>>>>>>>>>> + * @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);
--
Regards,
Laurent Pinchart
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