[Intel-gfx] [PATCH] drm/i915: Reset GMBUS controller after NAK

[Steven Newbury]

----- Original message -----
> On Thu, 31 Mar 2011 16:16:27 +0100, Steven Newbury
> <steve at snewbury.org.uk> wrote:
> > ----- Original message -----
> > > On Wed, 30 Mar 2011 17:07:11 +0100
> > > Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > > 
> > > > Once a NAK has been asserted by the slave, we need to reset the
> > > > GMBUS controller in order to continue. This is done by asserting
> > > > the Software Clear Interrupt bit and then clearing it again to
> > > > restore operations.
> > > > 
> > > > If we don't clear the NAK, then all future GMBUS xfers will fail,
> > > > including DDC probes and EDID retrieval.
> > > > 
> > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35781
> > > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > > ---
> > > 
> > > This one fixes the issue I was seeing on my HP test machine; LVDS DDC
> > > probing seems to work ok once this fix is applied.
> > > 
> > > -- 
> > Could this be related to my inability to successfully probe the ch7036
> > with the ChromeOS Chrontel driver? Is it worth me testing it again
> > with this patch applied? (I'm currently waiting to hear back from
> > Zotac, my board supplier)
> 
> Hmm. Depends, but unlikely. I would have thought the nm10_gpio driver
> you were using used it's only bitbanging on the GPIO lines rather than
> GMBUS. If in doubt, disable the use of GMBUS by 
> 
The GPIO is only used for HDMI hotplug detection, chip communication goes via i2c, or at least would if I could get it working... :-(