Re: [PATCH] drm/bridge_connector: enable HPD by default if supported

[Tomi Valkeinen]

Hi,

On 23/02/2022 19:02, Kieran Bingham wrote:
> Quoting Laurent Pinchart (2022-02-23 16:25:28)
> > Hello,
> >
> > On Wed, Feb 23, 2022 at 04:17:22PM +0000, Kieran Bingham wrote:
> > > Quoting Laurent Pinchart (2021-12-29 23:44:29)
> > > > On Sat, Dec 25, 2021 at 09:31:51AM +0300, Nikita Yushchenko wrote:
> > > > > Hotplug events reported by bridge drivers over drm_bridge_hpd_notify()
> > > > > get ignored unless somebody calls drm_bridge_hpd_enable(). When the
> > > > > connector for the bridge is bridge_connector, such a call is done from
> > > > > drm_bridge_connector_enable_hpd().
> > > > >
> > > > > However drm_bridge_connector_enable_hpd() is never called on init paths,
> > > > > documentation suggests that it is intended for suspend/resume paths.
> > > >
> > > > Hmmmm... I'm in two minds about this. The problem description is
> > > > correct, but I wonder if HPD should be enabled unconditionally here, or
> > > > if this should be left to display drivers to control.
> > > > drivers/gpu/drm/imx/dcss/dcss-kms.c enables HPD manually at init time,
> > > > other drivers don't.
> > > >
> > > > It feels like this should be under control of the display controller
> > > > driver, but I can't think of a use case for not enabling HPD at init
> > > > time. Any second opinion from anyone ?
> > >
> > > This patch solves an issue I have where I have recently enabled HPD on
> > > the SN65DSI86, but without this, I do not get calls to my .hpd_enable or
> > > .hpd_disable hooks that I have added to the ti_sn_bridge_funcs.
> > >
> > > So it needs to be enabled somewhere, and this seems reasonable to me?
> > > It's not directly related to the display controller - as it's a factor
> > > of the bridge?
> > >
> > > On Falcon-V3U with HPD additions to SN65DSI86:
> > > Tested-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> >
> > If you think this is right, then
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> I do, and at the very least it works for me, and fixes Nikita's issue so
> to me that's enough for:

So who disables the HPD now?

Is the drm_bridge_connector_enable_hpd & 
drm_bridge_connector_disable_hpd documentation now wrong as they talk 
about suspend/resume handlers?

 Tomi