Bug 45881

Created attachment 77361 [details]
Dmesg output

Can you attach an 'xrandr --verbose' for the working 3.4 setup?

Created attachment 77371 [details]
Output of xrandr --verbose using 3.4.8 kernel

Do you also want me to attach the output of 'xrandr --verbose' for the 3.5 kernel?

(In reply to comment #4)
> Do you also want me to attach the output of 'xrandr --verbose' for the 3.5
> kernel?

No, I was curious as to what the EDID should be. :)

Already reported here: https://lkml.org/lkml/2012/7/25/77

I've volunteered Jani to implement the workaround for it. Unfortunately he's not yet on kernel bugzilla, I'll yell at him a bit.

the patch suggested in the mailing list's thread solves the problem for me.

(In reply to comment #6)
> I've volunteered Jani to implement the workaround for it. Unfortunately he's
> not yet on kernel bugzilla, I'll yell at him a bit.

Yessir! I'm here now.

(In reply to comment #7)
> the patch suggested in the mailing list's thread solves the problem for me.

Please try the polished version posted in the list, and let use have your tested-by. Thanks.

I'll try to test it as soon as possible, but I'm not sure I'll be able to test it before Thursday.

Created attachment 77621 [details]
[PATCH 1/2] drm/i915: extract connector update from intel_ddc_get_modes() for reuse

Created attachment 77631 [details]
[PATCH 2/2] drm/i915: fall back to bit-banging if GMBUS fails in CRT EDID reads

second patch fails to apply HUNK #2 because there is a comment block between

i2c = intel_gmbus_get_adapter(dev_priv, dev_priv->crt_ddc_pin);
edid = drm_get_edid(connector, i2c);

and 

if (edid) {
 		bool is_digital = edid->input & DRM_EDID_INPUT_DIGITAL;


Anyway, changed manually that part and I'm currently building the kernel.

Problem seems to be solved with those two patches, however dmesg still gets "spammed" with [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 130

I'll attach the output of dmesg

Created attachment 77801 [details]
dmesg output after applying the two proposed patches

Thanks for the testing!

(In reply to comment #12)
> second patch fails to apply HUNK #2 because there is a comment block between
> 
> i2c = intel_gmbus_get_adapter(dev_priv, dev_priv->crt_ddc_pin);
> edid = drm_get_edid(connector, i2c);
> 
> and 
> 
> if (edid) {
>          bool is_digital = edid->input & DRM_EDID_INPUT_DIGITAL;
> 
> 
> Anyway, changed manually that part and I'm currently building the kernel.

I think this means you're applying the patch on top of kernel 3.5. Is that right? Before we apply the fix, I think it would be useful if you could test this on current master, or better yet, drm-intel-fixes branch of git://people.freedesktop.org/~danvet/drm-intel repo. Without and with the patches.

(In reply to comment #13)
> Problem seems to be solved with those two patches, however dmesg still gets
> "spammed" with [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid,
> remainder is 130

This is the GMBUS failure as before, but the patches add a fallback mechanism to use in this failure mode. If tried with the drm.debug=0xe module parameter, I think you'd see the "CRT GMBUS EDID read failed, retry using GPIO bit-banging" debug message.

Yes, I was applying the patch on top of 3.5, specifically 3.5.2 ( latest stable release)

I'll test it with drm-intel-fixes branch as soon as I can, but I fear it could not be possible until tomorrow.

Well, tested drm-intel-fixes branch from the git repo you posted and:

unpatched: dmesg gets spammed and the issue reported at the beginning of the thread exists.

patched: dmesg still gets spammed about the EDID checksum, but issue is gone

(In reply to comment #17)
> Well, tested drm-intel-fixes branch from the git repo you posted and:
> 
> unpatched: dmesg gets spammed and the issue reported at the beginning of the
> thread exists.
> 
> patched: dmesg still gets spammed about the EDID checksum, but issue is gone

Thanks again for testing. Daniel has queued the fix, and the dmesg spam will be looked into separately.

(In reply to comment #18)
> Thanks again for testing. Daniel has queued the fix, and the dmesg spam will
> be
> looked into separately.

Thank you for your time solving the issue. I'm glad I've been able to help

The fix landed in 3.6-rc2, cc: stable.

commit f1a2f5b7c5f0941d23eef0a095c0b99bf8d051e6
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Mon Aug 13 13:22:35 2012 +0300

    drm/i915: fall back to bit-banging if GMBUS fails in CRT EDID reads

A patch referencing this bug report has been merged in Linux v3.6-rc3:

commit 4eab81366465aedcfd26de960c595bc03599c09f
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Mon Aug 13 13:22:34 2012 +0300

    drm/i915: extract connector update from intel_ddc_get_modes() for reuse