Re: [coreboot] question on libgfxinit DP port number

[Nico Huber]

Hi Iru,

On 18.07.2017 09:28, Iru Cai wrote:
> Hi,
>
> I found the mainboard DP port doesn't have output before kernel starts in
> hp/2570p (https://review.coreboot.org/c/20489/). After I added DP3 and
> HDMI3 in port list, the DP port had output, and cbmem log said it's DP3.
> However, xrandr says this port is DP2. What is the problem?

libgfxinit only knows about physical ports (i.e. how they are ordered*
in the datasheet). Linux ignores ports that aren't strapped to be active
(or are disabled by VBT) and renumbers the ports to fill the holes.

Nico

* The numbering is not perfect. As historically VGA was the first port
  (port A in datasheets), digital ports are counted from B, so DP1 is
  port B, DP2 is port C, etc.

question on libgfxinit DP port number

[Iru Cai]

Thanks, Nico

On 2017年07月18日 16:20, Nico Huber wrote:
> Hi Iru,
>
> On 18.07.2017 09:28, Iru Cai wrote:
> > Hi,
> >
> > I found the mainboard DP port doesn't have output before kernel starts in
> > hp/2570p (https://review.coreboot.org/c/20489/). After I added DP3 and
> > HDMI3 in port list, the DP port had output, and cbmem log said it's DP3.
> > However, xrandr says this port is DP2. What is the problem?
>
> libgfxinit only knows about physical ports (i.e. how they are ordered*
> in the datasheet). Linux ignores ports that aren't strapped to be active
> (or are disabled by VBT) and renumbers the ports to fill the holes.
>
> Nico
> The numbering is not perfect. As historically VGA was the first port
> (port A in datasheets), digital ports are counted from B, so DP1 is
> port B, DP2 is port C, etc.

Now I found /sys/class/drm_dp_aux_dev/drm_dp_aux{0,1} (Linux 4.4) and
`cat /sys/class/drm_dp_aux_dev/*/name` gives me:
  DPDDC-B
  DPDDC-D

So should the ports be DP1 and DP3?

Iru

question on libgfxinit DP port number

[Nico Huber]

On 18.07.2017 11:05, Iru Cai wrote:
> Thanks, Nico
>
> On 2017年07月18日 16:20, Nico Huber wrote:
> > Hi Iru,
> >
> > On 18.07.2017 09:28, Iru Cai wrote:
> > > Hi,
> > >
> > > I found the mainboard DP port doesn't have output before kernel starts in
> > > hp/2570p (https://review.coreboot.org/c/20489/). After I added DP3 and
> > > HDMI3 in port list, the DP port had output, and cbmem log said it's DP3.
> > > However, xrandr says this port is DP2. What is the problem?
> >
> > libgfxinit only knows about physical ports (i.e. how they are ordered*
> > in the datasheet). Linux ignores ports that aren't strapped to be active
> > (or are disabled by VBT) and renumbers the ports to fill the holes.
> >
> > Nico
> > The numbering is not perfect. As historically VGA was the first port
> > (port A in datasheets), digital ports are counted from B, so DP1 is
> > port B, DP2 is port C, etc.
>
> Now I found /sys/class/drm_dp_aux_dev/drm_dp_aux{0,1} (Linux 4.4) and
> `cat /sys/class/drm_dp_aux_dev/*/name` gives me:
>   DPDDC-B
>   DPDDC-D
>
> So should the ports be DP1 and DP3?

Yes, likely (if mainboard and/or Linux aren't super weird and twist this
too).

Nico