Re: [PATCH 1/7] drm: Renaming DP training vswing pre emph defines

Thierry Reding
2014-08-27T13:09:05Z

[-- Attachment #1.1: Type: text/plain, Size: 1415 bytes --]

On Wed, Aug 27, 2014 at 08:51:35AM +0100, Damien Lespiau wrote:
> On Wed, Aug 27, 2014 at 08:47:54AM +0100, Damien Lespiau wrote:
> > > An alternative would be to provide a second set of defines for eDP 1.4
> > > where the name implies the meaning and then use them as appropriate.
> >
> > We went through the idea as well and:
> >
> > I actually think the nominal voltage swing and pre-emph values are quite
> > misleading. The hw is free to implement a wildly different set of voltage
> > swing/pre-emph values.
> >
> > eDP 1.4 changes those nominal values as described in the cover letter,
> > but there again, the actual hw implementation can choose fairly
> > different values than the nominal ones.
> >
> > Also, the DP 1.2 spec documents this field as (see address 103h):
> >
> > TRAINING_LANE0_SET : Link Training Control_Lane0
> > Bits 1:0 = VOLTAGE SWING SET
> > 00 –Voltage swing level 0
> > 01 –Voltage swing level 1
> > 10 –Voltage swing level 2
> > 11 –Voltage swing level 3
> >
> > So, in that sense, we're closer to the latest spec with those LEVEL_X
> > defines.
>
> I forgot to mention here that if we have separate defines for eDP 1.4,
> then we lose the possibility to share training code with big DP and eDP
> 1.3, not something desirable.

Yeah, I'd like to see the training sequences extracted into common
helpers.

Thierry

[-- Attachment #1.2: Type: application/pgp-signature, Size: 819 bytes --]

[-- Attachment #2: Type: text/plain, Size: 159 bytes --]

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org