[Intel-gfx] [PATCH 0/2] RFC: Potential improvements in edid detection timings (v2)
Eugeni Dodonov
eugeni.dodonov at intel.com
Sat Oct 8 00:00:40 CEST 2011
(Resending with small improvements - also sending to dri-devel for feedback).
This is the the forth iteration of potential fixes for slow edid detection
issues over non-existent outputs
(https://bugs.freedesktop.org/show_bug.cgi?id=41059) - the previous versions
were posted to the bug and were used mostly for debugging the problem.
The problem I attempted to fix here is that some systems would take a very
long time trying to locate all the possible video outputs - in in cases
where such outputs were bogus, this lead to timing out after all the
possible delays were done.
After investigation, I came to think on two different ways to fix the issue:
- The first patch does a one-line fix in drm_edid.c. I added a check for the
return value of i2c_transfer - and, if it is -ENXIO, we give up on further
attempts as the bus is not there. A drawback to this approach is that it
affects all the devices out there which use drm_get_edid. From my testing,
the -ENXIO gave no false positives, but I haven't tested it on non-Intel
cards. So I'd like to hear what other drm developers think about that.
- The second patch does a similar procedure within the i915 driver, in case
the proposed change to drm_edid.c won't be adequate for other drivers. It
adds a new function - intel_drm_get_valid_edid - which attempts to do a
simple i2c transfer over the bus prior to calling drm_get_edid. In case such
transfer fails with -ENXIO, it is a signal that the bus is not there, so we
shouldn't waste any time trying to communicate with it further.
Note that those patches provide lots of dmesg pollution - for the final
version those printk'ss should probably be removed, but I left them
intentionally with KERN_DEBUG in order to see when the adapters come and go
during the debugging and testing.
According to testing performed at
https://bugs.freedesktop.org/show_bug.cgi?id=41059, the following results
were obtained with those patches:
System1:
(testing all possible outputs)
ubuntu 3.0.0-12.19: 840ms
3.0.0-12.19 + drm patch: 290ms
3.0.0-12.19 + i915 patch: 290ms
(manually ignoring phantom outputs)
ubuntu 3.0.0-12.19: 690ms
3.0.0-12.19 + drm patch: 140ms
3.0.0-12.19 + i915 patch: 140ms
System2:
(testing all possible outputs)
ubuntu 3.0.0-12.19: 315ms
3.0.0-12.19 + drm patch: 280ms
3.0.0-12.19 + i915 patch: 280ms
(manually ignoring phantom outputs)
ubuntu 3.0.0-12.19: 175ms
3.0.0-12.19 + drm patch: 140ms
3.0.0-12.19 + i915 patch: 140ms
Eugeni Dodonov (2):
Give up on edid retries when i2c tells us that bus is not there
Check if the bus is valid prior to discovering edid.
drivers/gpu/drm/drm_edid.c | 5 +++++
drivers/gpu/drm/i915/intel_dp.c | 4 ++--
drivers/gpu/drm/i915/intel_drv.h | 2 ++
drivers/gpu/drm/i915/intel_hdmi.c | 4 ++--
drivers/gpu/drm/i915/intel_i2c.c | 33 +++++++++++++++++++++++++++++++++
drivers/gpu/drm/i915/intel_lvds.c | 2 +-
drivers/gpu/drm/i915/intel_modes.c | 2 +-
drivers/gpu/drm/i915/intel_sdvo.c | 4 ++--
8 files changed, 48 insertions(+), 8 deletions(-)
--
1.7.6.3
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