[PATCH RFC] drm: Add a new connector atomic property for link status
Sean Paul
seanpaul at chromium.org
Tue Nov 29 19:43:55 UTC 2016
On Tue, Nov 29, 2016 at 9:45 AM, Sean Paul <seanpaul at chromium.org> wrote:
> On Mon, Nov 28, 2016 at 7:59 PM, Manasi Navare
> <manasi.d.navare at intel.com> wrote:
>> On Wed, Nov 23, 2016 at 09:09:28AM +0100, Daniel Vetter 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 at intel.com> 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 at linux.intel.com>
>>> > > Cc: Daniel Vetter <daniel.vetter at intel.com>
>>> > > Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
>>> > > Cc: Chris Wilson <chris at chris-wilson.co.uk>
>>> > > Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
>>> > > ---
>>> > > 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;
>>> 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().
While I'm nitpicking documentation, I think this one needs work, too.
I'd prefer you just describe what the property conveys here instead of
getting into driver implementation specifics. So something like:
* link-status
* Connector link-status property to indicate the status of link. The
* default value is "GOOD". If something fails during, or after modeset,
* the driver may set this to "BAD" and issue a hotplug uevent. Drivers
* should update this value using
* drm_mode_connector_set_link_status_property()
Sean
>>> > > * 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?
>>> >
>>
>> Sean, do you have any recommendations on the text that can go in the kernel doc for
>> this property to clarify that it depends on the kernel implementation whether we want
>> to use this link-status property to do the retraining or not. Leaving it BAD and not doing
>> anything will be fine too.
>>
>
> I'd prefer something like:
>
> * In usual working scenario, this link status property will always be set to
> * "GOOD". If something fails during or after a mode set, the driver may
> * set this property to "BAD". The caller then needs to send a hotplug uevent
> * for userspace to re-check the valid modes through GET_CONNECTOR_IOCTL and
> * retry modeset.
> *
> * Note: Drivers can not rely on userspace to support this property and
> * issue a modeset. As such, they may choose to handle issues (like re-training
> * a link) without userspace's intervention.
>
>
> The difference being that we don't need to mention modes since that
> will be handled through the normal avenue and we don't necessarily
> want to remove any modes from the list.
>
> Sean
>
>
>> Manasi
>>> > > + * 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?
>>>
>>> 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
>>> > >
>>> > > _______________________________________________
>>> > > dri-devel mailing list
>>> > > dri-devel at lists.freedesktop.org
>>> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>> > _______________________________________________
>>> > dri-devel mailing list
>>> > dri-devel at lists.freedesktop.org
>>> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> http://blog.ffwll.ch
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