[PATCH RFC] drm: Add a new connector atomic property for link status
Sean Paul
seanpaul at chromium.org
Wed Nov 23 14:40:29 UTC 2016
On Wed, Nov 23, 2016 at 3:09 AM, Daniel Vetter <daniel at ffwll.ch> 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;
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.
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
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