[Intel-gfx] [PATCH 3/3] drm/i915: set the LPT FDI RX polarity reversal bit when needed

[Daniel Vetter]

On Sun, Dec 09, 2012 at 07:37:40PM -0200, Paulo Zanoni wrote:
> Hi
> 
> 2012/12/8 Damien Lespiau <damien.lespiau at intel.com>:
> > On Sat, Dec 1, 2012 at 2:04 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> >>
> >> If we fail to set the bit when needed we get some nice FDI link
> >> training failures (AKA "black screen on VGA output").
> >>
> >> While we don't really know how to properly choose whether we need to
> >> set the bit or not (VBT?), just read the initial value set by the BIOS
> >> and store it for later usage.
> >>
> >> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> >
> > Sad that we did not catch that before. It's not just the polarity
> > (support for exchanging the - and + wires on a differential pair), but
> > also the FDI lane reversal (0 becomes 3, 1 becomes 2) setting that we
> > need to preserve. There's a fused bit for the DMI lane reversal and
> > FDI defaults to following that DMI lane reversal configuration, but we
> > also have a bit to override that behaviour in the FDI RX register, we
> > need to preserve this bit  as well.
> 
> They're different problems and require different patches. This one
> fixes the "FDI RX polarity" problem, not "lane reversal".

Picked up for -fixes (together with patch 1), thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch