Re: [PATCH 1/3] drm/dp: make aux retries less chatty

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Mar 19, 2014 at 09:42:44AM -0400, Alex Deucher wrote:
> On Tue, Mar 18, 2014 at 3:44 AM, Jani Nikula
> <jani.nikula@linux.intel.com> wrote:
> > On Tue, 18 Mar 2014, Alex Deucher <alexdeucher@gmail.com> wrote:
> >> Switch to debug only to avoid flooding the logs.
> >> This mirrors the behavior in some other drivers.
> >
> > I'd rather think we should find out why the DP devices are replying with
> > repeated native or i2c-over-aux defers. This doesn't help; I'm not in
> > favour.
> 
> While I agree with you in theory, in practice this will generate a ton
> of regression bug reports since there will be new error messages in
> the kernel log on some systems even though the displays are working
> fine.  I'm only seeing this on certain cards, others are perfectly
> fine even with the same monitors and I don't have the bandwidth right
> now to debug this further.  In all cases the monitors are working
> correctly.

Yeah, as a stopgap I'm ok with this. I guess longer-term we might want to
cache parts of the DPCD in the helper and provide an invalidate function
which drivers can call on hotplug. With that the dp aux helper could be a
bit more intelligent with non-native syncs.

One of the things I want to push down a bit into helpers is the
branch/sink decoding and figuring out whether we have some legacy thing
where hotplug pins might be busted or which need massively longer delays.

Anyway Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Btw I've just
pulled in Jani's conversion for i915, so we should have a few big drivers
using all this with 3.15. I hope all the increased test coverage pays off
;-)

Cheers, Daniel

> 
> Alex
> 
> >
> > BR,
> > Jani.
> >
> >
> >>
> >> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> >> ---
> >>  drivers/gpu/drm/drm_dp_helper.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> >> index 35251af..74724aa 100644
> >> --- a/drivers/gpu/drm/drm_dp_helper.c
> >> +++ b/drivers/gpu/drm/drm_dp_helper.c
> >> @@ -402,7 +402,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
> >>               }
> >>       }
> >>
> >> -     DRM_ERROR("too many retries, giving up\n");
> >> +     DRM_DEBUG_KMS("too many retries, giving up\n");
> >>       return -EIO;
> >>  }
> >>
> >> @@ -656,7 +656,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> >>               }
> >>       }
> >>
> >> -     DRM_ERROR("too many retries, giving up\n");
> >> +     DRM_DEBUG_KMS("too many retries, giving up\n");
> >>       return -EREMOTEIO;
> >>  }
> >>
> >> --
> >> 1.8.3.1
> >>
> >> _______________________________________________
> >> dri-devel mailing list
> >> dri-devel@lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> > --
> > Jani Nikula, Intel Open Source Technology Center
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> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch