On Mon, Sep 11, 2023 at 2:15 PM Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> wrote: > > On 06/09/2023 16:38, Heikki Krogerus wrote: > > On Wed, Sep 06, 2023 at 03:48:35PM +0300, Dmitry Baryshkov wrote: > >> On Wed, 6 Sept 2023 at 15:44, Heikki Krogerus > >> <heikki.krogerus@xxxxxxxxxxxxxxx> wrote: > >>> > >>> On Tue, Sep 05, 2023 at 01:56:59PM +0300, Dmitry Baryshkov wrote: > >>>> Hi Heikki, > >>>> > >>>> On Tue, 5 Sept 2023 at 11:50, Heikki Krogerus > >>>> <heikki.krogerus@xxxxxxxxxxxxxxx> wrote: > >>>>> > >>>>> Hi Dmitry, > >>>>> > >>>>> On Mon, Sep 04, 2023 at 12:41:39AM +0300, Dmitry Baryshkov wrote: > >>>>>> The kdev->fwnode pointer is never set in drm_sysfs_connector_add(), so > >>>>>> dev_fwnode() checks never succeed, making the respective commit NOP. > >>>>> > >>>>> That's not true. The dev->fwnode is assigned when the device is > >>>>> created on ACPI platforms automatically. If the drm_connector fwnode > >>>>> member is assigned before the device is registered, then that fwnode > >>>>> is assigned also to the device - see drm_connector_acpi_find_companion(). > >>>>> > >>>>> But please note that even if drm_connector does not have anything in > >>>>> its fwnode member, the device may still be assigned fwnode, just based > >>>>> on some other logic (maybe in drivers/acpi/acpi_video.c?). > >>>>> > >>>>>> And if drm_sysfs_connector_add() is modified to set kdev->fwnode, it > >>>>>> breaks drivers already using components (as it was pointed at [1]), > >>>>>> resulting in a deadlock. Lockdep trace is provided below. > >>>>>> > >>>>>> Granted these two issues, it seems impractical to fix this commit in any > >>>>>> sane way. Revert it instead. > >>>>> > >>>>> I think there is already user space stuff that relies on these links, > >>>>> so I'm not sure you can just remove them like that. If the component > >>>>> framework is not the correct tool here, then I think you need to > >>>>> suggest some other way of creating them. > >>>> > >>>> The issue (that was pointed out during review) is that having a > >>>> component code in the framework code can lead to lockups. With the > >>>> patch #2 in place (which is the only logical way to set kdev->fwnode > >>>> for non-ACPI systems) probing of drivers which use components and set > >>>> drm_connector::fwnode breaks immediately. > >>>> > >>>> Can we move the component part to the respective drivers? With the > >>>> patch 2 in place, connector->fwnode will be copied to the created > >>>> kdev's fwnode pointer. > >>>> > >>>> Another option might be to make this drm_sysfs component registration optional. > >>> > >>> You don't need to use the component framework at all if there is > >>> a better way of determining the connection between the DP and its > >>> Type-C connector (I'm assuming that that's what this series is about). > >>> You just need the symlinks, not the component. > >> > >> The problem is that right now this component registration has become > >> mandatory. And if I set the kdev->fwnode manually (like in the patch > >> 2), the kernel hangs inside the component code. > >> That's why I proposed to move the components to the place where they > >> are really necessary, e.g. i915 and amd drivers. > > > > So why can't we replace the component with the method you are > > proposing in this series of finding out the Type-C port also with > > i915, AMD, or whatever driver and platform (that's the only thing that > > component is used for)? > > The drm/msm driver uses drm_bridge for the pipeline (including the last > DP entry) and the drm_bridge_connector to create the connector. I think > that enabling i915 and AMD drivers to use drm_bridge fells out of scope > for this series. > > > > Determining the connection between a DP and its Type-C connector is > > starting to get really important, so ideally we have a common solution > > for that. > > Yes. This is what we have been discussing with Simon for quite some time > on #dri-devel. > > Unfortunately I think the solution that got merged was pretty much > hastened in instead of being well-thought. For example, it is also not > always possible to provide the drm_connector / typec_connector links (as > you can see from the patch7. Sometimes we can only express that this is > a Type-C DP connector, but we can not easily point it to the particular > USB-C port. > > So, I'm not sure, how can we proceed here. Currently merged patch breaks > drm/msm if we even try to use it by setting kdef->fwnode to > drm_connector->fwnode. The pointed out `drivers/usb/typec/port-mapper.c` > is an ACPI-only thing, which is not expected to work in a non-ACPI cases. In these cases we revert and try again next cycle BR, -R > > -- > With best wishes > Dmitry >
