RE: [PATCH 2/4] drm/dp_mst: Don't cache EDIDs for physical ports

["Lin, Wayne" <Wayne.Lin@amd.com>]

[AMD Official Use Only - Internal Distribution Only]

> -----Original Message-----
> From: Imre Deak <imre.deak@intel.com>
> Sent: Tuesday, February 2, 2021 7:22 PM
> To: Lin, Wayne <Wayne.Lin@amd.com>
> Cc: dri-devel@lists.freedesktop.org; Lyude Paul <lyude@redhat.com>
> Subject: Re: [PATCH 2/4] drm/dp_mst: Don't cache EDIDs for physical ports
>
> On Tue, Feb 02, 2021 at 03:38:16AM +0000, Lin, Wayne wrote:
> > [AMD Public Use]
> >
> > > -----Original Message-----
> > > From: Imre Deak <imre.deak@intel.com>
> > > Sent: Monday, February 1, 2021 8:02 PM
> > > To: dri-devel@lists.freedesktop.org
> > > Cc: Lin, Wayne <Wayne.Lin@amd.com>; Lyude Paul <lyude@redhat.com>
> > > Subject: [PATCH 2/4] drm/dp_mst: Don't cache EDIDs for physical
> > > ports
> > >
> > > Caching EDIDs for physical ports prevents updating the EDID if a
> > > port gets reconnected via a Connection Status Notification message, fix this.
> > >
> > > Fixes: db1a07956968 ("drm/dp_mst: Handle SST-only branch device
> > > case")
> > > Cc: Wayne Lin <Wayne.Lin@amd.com>
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > ---
> > >  drivers/gpu/drm/drm_dp_mst_topology.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > index deb7995f42fa..309afe61afdd 100644
> > > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > > @@ -2302,7 +2302,8 @@ drm_dp_mst_port_add_connector(struct
> > > drm_dp_mst_branch *mstb,  }
> > >
> > >  if (port->pdt != DP_PEER_DEVICE_NONE &&
> > > -    drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
> > > +    drm_dp_mst_is_end_device(port->pdt, port->mcs) &&
> > > +    port->port_num >= DP_MST_LOGICAL_PORT_0) {
> > Hi Imre Deak,
> >
> > Thanks for the patch!
> > Just curious that you mean we don't want to fetch the EDID of the sst
> > monitor like below case?
> >
> >     Src->MST device ->SST monitor
>
> The intention of the mst cached_edid logic is to cache the EDID for logical ports where the EDID cannot change anyway. The EDID on
> physical ports is fetched during connector probing just as for any other connector.
>
> > I thought we still need to get the EDID even the monitor is connected
> > to the physical output port of mst device.
>
> For sinks attached to phyisical ports we get the EDID whenever probing the corresponding connector.
>
> > Maybe what we should fix here is why the EDID is not get updated once
> > reconnected via CSN message?
>
> This patch fixes the problem that we stopped updating the EDID for physical connectors. After this change it will get updated when
> probing such connectors.
>
Appreciate for the explanation.
Thanks!
> > Thanks!
> > >  port->cached_edid = drm_get_edid(port->connector,
> > >   &port->aux.ddc);
> > >  drm_connector_set_tile_property(port->connector);
> > > --
> > > 2.25.1
> > Regards,
> > Wayne Lin
Regards,
Wayne Lin
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