[Intel-gfx] [PATCH] drm/i915: Fix the HDMI hot plug disconnection failure (v4)

[Guang Bai]

On Wed, 2 Jan 2019 17:29:46 +0800
Chris Chiu <chiu at endlessm.com> wrote:

> Happy New Year.
> Sorry for bothering you guys again, I don't really want to make myself
> a nuisance.
> Is there any better idea for fixing this issue?
I've already back ported this change into the kernel 4.18.17 and sent
it to our customer for integration test - So far so good.
Thanks,
-Guang
> 
> Chris
> 
> On Mon, Dec 3, 2018 at 6:38 PM Chris Chiu <chiu at endlessm.com> wrote:
> >
> > On Fri, Nov 30, 2018 at 1:15 AM Guang Bai <guang.bai at intel.com>
> > wrote:  
> > >
> > > On Thu, 29 Nov 2018 10:17:49 +0200
> > > Jani Nikula <jani.nikula at intel.com> wrote:
> > >  
> > > > On Wed, 28 Nov 2018, Guang Bai <guang.bai at intel.com> wrote:  
> > > > > On some GEN9 platforms, slowly unplugging (wiggling) the HDMI
> > > > > cable makes the kernel to believe the HDMI display is still
> > > > > connected. This is because the HDMI DDC lines are
> > > > > disconnected a little bit later after the hot-plug interrupt
> > > > > triggered thus an immediate edid fetch can be made. This
> > > > > problem has been identified by more than one customer
> > > > > recently. Use digital port live states to authorize the edid
> > > > > read at HDMI detection point will ensure most of the display
> > > > > related software states updated and rest of them will be
> > > > > renewed accordingly when the port is connected.
> > > > >
> > > > > v2: Fix the formatting issue
> > > > > v3: Use digital port states to authorize the edid read
> > > > > v4: Add comments on issue histories and rationale of the fix
> > > > > (Chris W)  
> > > >
> > > > You're not answering Chris Wilson's question.
> > > >
> > > > Why do you think the problems we've historically had with live
> > > > status are no longer a problem? We've tried and reverted live
> > > > status checks at least twice before because of regressions. Why
> > > > do you think this time there won't be regressions? Why do you
> > > > think this patch makes forward progress?  
> > > Jani,
> > > I'm still new to kernel developments compared with all of you
> > > working in this area for many years - Haven't got any feedbacks
> > > on how exactly the HDMI live statue *not* fit for HDMI hot-plug
> > > related port status checking, neither had time to track all
> > > upstream bugzilla, plus not working directly with Intel OTC teams
> > > - What are those failing cases/regressions you mentioned above?
> > > - what were the kernel versions related with those developments?
> > > - Given the fact i915 architecture and implementation are
> > > constantly evolving - Should we re-visit those issues with
> > > current kernel implementation?
> > > - Fundamentally, do you think the edid fetch is still *valid*
> > > when the HDMI is unplugged (status either from PCH or DE)? Or
> > > other platform configurations may present more complexities such
> > > as kvm switches are used along with HDMI?
> > > Again, if you could provide me more historical issue details, I'd
> > > like to have some reviews/re-investigation for those cases with
> > > current 4.20 kernel.
> > > Thanks,
> > > -Guang  
> >
> > Hi Jani,
> >     I don't know the history and what kind of painful regression
> > that you had run into. Could you maybe provide a test plan or some
> > test cases for the regression verification? I can follow steps to
> > try to verify whether if the patch can work on all cases.
> >
> > Chris
> >  
> > > >
> > > > I've *repeatedly* said from the beginning that I am very
> > > > sceptical of using live status because we've been burned by it
> > > > so many times before. I don't much care to repeat this anymore.
> > > >
> > > >
> > > > BR,
> > > > Jani.
> > > >
> > > >  
> > > > >
> > > > > Cc: Jani Nikula <jani.nikula at intel.com>
> > > > > Cc: Chris Chiu <chiu at endlessm.com>
> > > > > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > > > > Signed-off-by: Guang Bai <guang.bai at intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/i915/intel_hdmi.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> > > > > b/drivers/gpu/drm/i915/intel_hdmi.c index e2c6a2b..8cf7c78
> > > > > 100644 --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > > > > @@ -1929,7 +1929,7 @@ intel_hdmi_detect(struct drm_connector
> > > > > *connector, bool force)
> > > > >     intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
> > > > >
> > > > > -   if (IS_ICELAKE(dev_priv) &&
> > > > > +   if ((IS_ICELAKE(dev_priv) || IS_GEN9_BC(dev_priv)) &&
> > > > >         !intel_digital_port_connected(encoder))
> > > > >             goto out;  
> > > >  
> > >