[PATCH RFC] drm: Add a new connector atomic property for link status
Sean Paul
seanpaul at chromium.org
Wed Nov 23 16:09:16 UTC 2016
On Wed, Nov 23, 2016 at 10:52 AM, Jani Nikula
<jani.nikula at linux.intel.com> wrote:
> On Wed, 23 Nov 2016, Sean Paul <seanpaul at chromium.org> wrote:
>> On Wed, Nov 23, 2016 at 10:15 AM, Jani Nikula
>> <jani.nikula at linux.intel.com> wrote:
>>> On Wed, 23 Nov 2016, Sean Paul <seanpaul at chromium.org> wrote:
>>>> 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.
>>>
>>> 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 :)
>
> And just because I want to, doesn't mean I can! ;)
>
Truth. Many people have tried and failed :-D
>> 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
>
> I think so.
>
>> and rip re-training out of the various kernel drivers?
>
> IMO if it works, don't change it, at least not in a rush. It also
> depends on the hardware and the driver; the amount of code required may
> be vastly different for various drivers.
>
> Personally, I think in the long run letting userspace help here leads to
> a simpler design and more efficient happy day scenario handling, and
> userspace knows what's going on.
>
Agreed on this.
I wish there were an easier way for drivers to do the right thing, but
I suppose we can struggle on until userspace supports this :/
Sean
> BR,
> Jani.
>
>>
>> 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
>>>>>> >
>>>>>> > _______________________________________________
>>>>>> > 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
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel at lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>> --
>>> Jani Nikula, Intel Open Source Technology Center
>
> --
> Jani Nikula, Intel Open Source Technology Center
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