On Wed, Nov 23, 2016 at 10:15 AM, Jani Nikula
<jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Wed, 23 Nov 2016, Sean Paul <seanpaul@xxxxxxxxxxxx> wrote:
>> On Wed, Nov 23, 2016 at 3:09 AM, Daniel Vetter <daniel@xxxxxxxx> wrote:
>>> On Tue, Nov 22, 2016 at 09:27:35PM -0500, Sean Paul wrote:
>>>> On Tue, Nov 22, 2016 at 8:30 PM, Manasi Navare
>>>> <manasi.d.navare@xxxxxxxxx> wrote:
>>>> > This is RFC patch for adding a connector link-status property
>>>> > and making it atomic by adding it to the drm_connector_state.
>>>> > This is to make sure its wired properly in drm_atomic_connector_set_property
>>>> > and drm_atomic_connector_get_property functions.
>>>> >
>>>>
>>>> Thanks for sending this. We ran into some re-training awkwardness
>>>> recently, and I
>>>> was hoping for such a patch.
>>>>
>>>> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
>>>> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
>>>> > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>>>> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>>>> > Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
>>>> > ---
>>>> > drivers/gpu/drm/drm_atomic.c | 5 ++++
>>>> > drivers/gpu/drm/drm_connector.c | 65 +++++++++++++++++++++++++++++++++++++++--
>>>> > include/drm/drm_connector.h | 12 +++++++-
>>>> > include/drm/drm_mode_config.h | 5 ++++
>>>> > include/uapi/drm/drm_mode.h | 4 +++
>>>> > 5 files changed, 88 insertions(+), 3 deletions(-)
>>>> >
>>>> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>>>> > index 89737e4..644d19f 100644
>>>> > --- a/drivers/gpu/drm/drm_atomic.c
>>>> > +++ b/drivers/gpu/drm/drm_atomic.c
>>>> > @@ -1087,6 +1087,9 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>>>> > * now?) atomic writes to DPMS property:
>>>> > */
>>>> > return -EINVAL;
>>>> > + } else if (property == config->link_status_property) {
>>>> > + state->link_status = val;
>>>
>>> I think we should have a check here to make sure userspace never tries to
>>> set this from "GOOD" to "BAD". "BAD" to "BAD" we need to allow, since with
>>> atomic userspace is supposed to be able to just restore everything to what
>>> it was.
>>>
>>> I don't think trying to set it to "BAD" should cause an error though, just
>>> silently keep the link status at "GOOG". So:
>>>
>>> /* Never downgrade from GOOD to BAD on userspace's request here,
>>> * only hw issues can do that. */
>>> if (state->link_status == GOOD)
>>> return 0;
>>
>> Can we return an error if the transition is invalid?
>>
>>> state->link_status = val;
>>> return 0;
>>>
>>>> > + return 0;
>>>> > } else if (connector->funcs->atomic_set_property) {
>>>> > return connector->funcs->atomic_set_property(connector,
>>>> > state, property, val);
>>>> > @@ -1135,6 +1138,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>>>> > *val = (state->crtc) ? state->crtc->base.id : 0;
>>>> > } else if (property == config->dpms_property) {
>>>> > *val = connector->dpms;
>>>> > + } else if (property == config->link_status_property) {
>>>> > + *val = state->link_status;
>>>> > } else if (connector->funcs->atomic_get_property) {
>>>> > return connector->funcs->atomic_get_property(connector,
>>>> > state, property, val);
>>>> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
>>>> > index 5a45262..4576c9f 100644
>>>> > --- a/drivers/gpu/drm/drm_connector.c
>>>> > +++ b/drivers/gpu/drm/drm_connector.c
>>>> > @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>>>> > drm_object_attach_property(&connector->base,
>>>> > config->dpms_property, 0);
>>>> >
>>>> > + drm_object_attach_property(&connector->base,
>>>> > + config->link_status_property,
>>>> > + 0);
>>>> > +
>>>> > if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>>>> > drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>>>> > }
>>>> > @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>>>> > };
>>>> > DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>>>> >
>>>> > +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
>>>> > + { DRM_MODE_LINK_STATUS_GOOD, "Good" },
>>>> > + { DRM_MODE_LINK_STATUS_BAD, "Bad" },
>>>> > +};
>>>> > +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
>>>> > +
>>>> > /**
>>>> > * drm_display_info_set_bus_formats - set the supported bus formats
>>>> > * @info: display info to store bus formats in
>>>> > @@ -616,7 +626,7 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>>>> > * path property the MST manager created. Userspace cannot change this
>>>> > * property.
>>>> > * TILE:
>>>> > - * Connector tile group property to indicate how a set of DRM connector
>>>> > + * Connector tile group property to indicate how a set of DRM connector
>>>>
>>>> keyboard slip here
>>>>
>>>> > * compose together into one logical screen. This is used by both high-res
>>>> > * external screens (often only using a single cable, but exposing multiple
>>>> > * DP MST sinks), or high-res integrated panels (like dual-link DSI) which
>>>> > @@ -625,7 +635,14 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>>>> > * tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>>>> > * should update this value using drm_mode_connector_set_tile_property().
>>>> > * Userspace cannot change this property.
>>>> > - *
>>>> > + * link-status:
>>>> > + * Connector link-status property to indicate the status of link during
>>>> > + * the modeset. The default value of link-status is "GOOD". If something
>>>> > + * fails during modeset, the kernel driver can set this to "BAD", prune
>>>> > + * the mode list based on new link parameters and send a hotplug uevent
>>>> > + * to notify userspace to re-check the valid modes through GET_CONNECTOR
>>>> > + * IOCTL and redo a modeset. Drivers should update this value using
>>>> > + * drm_mode_connector_set_link_status_property().
>>>> > * Connectors also have one standardized atomic property:
>>>> > *
>>>> > * CRTC_ID:
>>>> > @@ -666,6 +683,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>>>> > return -ENOMEM;
>>>> > dev->mode_config.tile_property = prop;
>>>> >
>>>> > + prop = drm_property_create_enum(dev, DRM_MODE_PROP_ATOMIC, "link-status",
>>>> > + drm_link_status_enum_list,
>>>> > + ARRAY_SIZE(drm_link_status_enum_list));
>>>> > + if (!prop)
>>>> > + return -ENOMEM;
>>>> > + dev->mode_config.link_status_property = prop;
>>>> > +
>>>> > return 0;
>>>> > }
>>>> >
>>>> > @@ -995,6 +1019,43 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>>>> > }
>>>> > EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>>>> >
>>>> > +/**
>>>> > + * drm_mode_connector_set_link_status_property - Set link status property of a connector
>>>> > + * @connector: drm connector
>>>> > + * @link_status: new value of link status property (0: Good, 1: Bad)
>>>> > + *
>>>> > + * In usual working scenario, this link status property will always be set to
>>>> > + * "GOOD". If something fails during or after a mode set, the kernel driver should
>>>> > + * set this link status property to "BAD" and prune the mode list based on new
>>>>
>>>> Does the mode list really *need* to be pruned? In the case of needing
>>>> to re-train a DP link,
>>>> it seems like we should be able to set this BAD and keep the modelist
>>>> as-is (since the sink
>>>> hasn't changed)
>>>
>>> Well, if you prune it with the same constraints as before, no additional
>>> modes will be removed and the same list is there. Pruning here refers to
>>> the ->mode_valid step as done in e.g. drm_helper_probe_single_connector_modes.
>>>
>>> We might want to be a bit more explicit here perhaps? Have some good
>>> proposal text to insert?
>>
>> Ah, hmm, I hadn't equated this prune to the normal drm_connector
>> prune_invalid. I suppose the "based on new information" is what did
>> it. It seems like the mode_valid pruning will happen automagically
>> when userspace realizes the connection is BAD and asks for a new mode
>> list. So is it worth even mentioning pruning the mode list?
>>
>>>>
>>>> > + * information. The caller then needs to send a hotplug uevent for userspace to
>>>> > + * re-check the valid modes through GET_CONNECTOR_IOCTL and retry modeset.
>>>>
>>>> extra space
>>>>
>>>> > + *
>>>> > + * Note that a lot of existing userspace do not handle this property.
>>>> > + * Drivers can therefore not rely on userspace to fix up everything and
>>>> > + * should try to handle issues (like just re-training a link) without
>>>> > + * userspace's intervention. This should only be used when the current mode
>>>> > + * fails and userspace must select a different display mode.
>>>>
>>>> Hmm, I suppose this answers my last question. It's too bad we can't
>>>> rely on this, since we'll
>>>> just end up with each driver rolling their own re-training logic on
>>>> top of possibly supporting
>>>> this (but probably not, since it's really just overhead). Perhaps this
>>>> is an overly pessimistic
>>>> view?
>>>
>>> You can forgo any re-training of course, that should work too. It's just
>>> that DP spec and everyone else seem to recommend to at least do some
>>> minimal effort (or maybe even upfront link training) here. But totally not
>>> doing anything if the link is bad should be ok too (and probably really
>>> simple to implement for drivers, maybe even with a dp_hpd_handler() helper
>>> function which checks link status and set link-status to bad&fires off the
>>> uevent if needed.
>>>
>>> Again, do you have some sample prose to add here to clarify this?
>>>
>>
>> I don't think it's merely a matter of clarifying the comment, tbh.
>> Without relying on userspace to fix us, there's not much point in
>> exposing the property in the first place.
>>
>> As a driver author, I need to decide whether I want re-training to
>> work properly. If I do, I need to handroll it in my driver since I
>> can't rely on userspace, at which point, implementing the property
>> isn't meaningful. If I don't care about it being bulletproof, I can
>> expose the property and let userspace fix me if they know how.
>>
>> So I'd prefer to have the helper be a hybrid between this patch and
>> the previous one that did a full modeset under the covers (perhaps
>> with a client cap or similar to let us know which path to trust). That
>> way I can call the helper from my driver and know that I'm going to be
>> re-trained either way.
>
> If your driver is able to handle everything in kernel, then do so by all
> means. If it can't, defer to userspace, which may or may not fix stuff,
> depending on whether it looks at the property. If the userspace doesn't
> do anything, things will be just as good or bad as they are currently,
> before this property.
>
> This allows the drivers to choose how much they can/want to do in
> kernel, and what they defer to userspace.
>
Just because I can, doesn't mean I want to :)
Take the CDN DP driver in rockchip for example (posted yesterday).
There's a worker in the driver that is responsible for handling
hpd/extcon events from the USB-C port. Ideally, this worker should
just be a thin shell around a kms uevent that lets userspace know
there's been a change. Unfortunately since we need to make re-training
work (/me grumbles about productization) seamlessly, we need to add a
bunch of goo into the worker to handle re-training. Since we need to
handle re-training there and in modeset, we need to properly
synchronize things. So we end up with a bunch of code that doesn't
*really* need to be there.
So is the correct path forward to add GOOD/BAD connection handling to
Chrome/drm_hwc and rip re-training out of the various kernel drivers?
Sean
> BR,
> Jani.
>
>
>
>>
>> Sean
>>
>>
>>> Thanks for taking a look at this.
>>>
>>> Cheers, Daniel
>>>
>>>> > + * The DRM driver can chose to not modify property and keep link status
>>>> > + * as "GOOD" always to keep the user experience same as it currently is.
>>>> > + *
>>>> > + * The reason for adding this property is to handle link training failures, but
>>>> > + * it is not limited to DP or link training. For example, if we implement
>>>> > + * asynchronous setcrtc, this property can be used to report any failures in that.
>>>> > + */
>>>> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
>>>> > + uint64_t link_status)
>>>> > +{
>>>> > + struct drm_device *dev = connector->dev;
>>>> > +
>>>> > + /* Make sure the mutex is grabbed */
>>>> > + lockdep_assert_held(&dev->mode_config.mutex);
>>>> > + connector->link_status = link_status;
>>>> > + drm_object_property_set_value(&connector->base,
>>>> > + dev->mode_config.link_status_property,
>>>> > + link_status);
>>>> > +}
>>>> > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
>>>> > +
>>>> > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>>>> > struct drm_property *property,
>>>> > uint64_t value)
>>>> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
>>>> > index 34f9741..3d513ab 100644
>>>> > --- a/include/drm/drm_connector.h
>>>> > +++ b/include/drm/drm_connector.h
>>>> > @@ -213,6 +213,9 @@ struct drm_connector_state {
>>>> >
>>>> > struct drm_encoder *best_encoder;
>>>> >
>>>> > + /* Connector Link status */
>>>> > + unsigned int link_status;
>>>> > +
>>>> > struct drm_atomic_state *state;
>>>> > };
>>>> >
>>>> > @@ -695,6 +698,12 @@ struct drm_connector {
>>>> > uint8_t num_h_tile, num_v_tile;
>>>> > uint8_t tile_h_loc, tile_v_loc;
>>>> > uint16_t tile_h_size, tile_v_size;
>>>> > +
>>>> > + /* Connector Link status
>>>> > + * 0: If the link is Good
>>>> > + * 1: If the link is Bad
>>>> > + */
>>>> > + int link_status;
>>>> > };
>>>> >
>>>> > #define obj_to_connector(x) container_of(x, struct drm_connector, base)
>>>> > @@ -767,12 +776,13 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
>>>> > int drm_mode_create_scaling_mode_property(struct drm_device *dev);
>>>> > int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
>>>> > int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
>>>> > -
>>>>
>>>> lost a line here
>>>>
>>>> > int drm_mode_connector_set_path_property(struct drm_connector *connector,
>>>> > const char *path);
>>>> > int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>>>> > int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>>>> > const struct edid *edid);
>>>> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
>>>> > + uint64_t link_status);
>>>> >
>>>> > /**
>>>> > * struct drm_tile_group - Tile group metadata
>>>> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
>>>> > index bf9991b..86faee4 100644
>>>> > --- a/include/drm/drm_mode_config.h
>>>> > +++ b/include/drm/drm_mode_config.h
>>>> > @@ -431,6 +431,11 @@ struct drm_mode_config {
>>>> > */
>>>> > struct drm_property *tile_property;
>>>> > /**
>>>> > + * @link_status_property: Default connector property for link status
>>>> > + * of a connector
>>>> > + */
>>>> > + struct drm_property *link_status_property;
>>>> > + /**
>>>> > * @plane_type_property: Default plane property to differentiate
>>>> > * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>>>> > */
>>>> > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>>>> > index 728790b..309c478 100644
>>>> > --- a/include/uapi/drm/drm_mode.h
>>>> > +++ b/include/uapi/drm/drm_mode.h
>>>> > @@ -123,6 +123,10 @@
>>>> > #define DRM_MODE_DIRTY_ON 1
>>>> > #define DRM_MODE_DIRTY_ANNOTATE 2
>>>> >
>>>> > +/* Link Status options */
>>>> > +#define DRM_MODE_LINK_STATUS_GOOD 0
>>>> > +#define DRM_MODE_LINK_STATUS_BAD 1
>>>> > +
>>>> > struct drm_mode_modeinfo {
>>>> > __u32 clock;
>>>> > __u16 hdisplay;
>>>> > --
>>>> > 1.9.1
>>>> >
>>>> > _______________________________________________
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>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> http://blog.ffwll.ch
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Jani Nikula, Intel Open Source Technology Center
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