This allows to avoid talking to a non-responding bus repeatedly until we finally timeout after 15 attempts. We can do this by catching the -ENXIO error, provided by i2c_algo_bit:bit_doAddress call.
Within the bit_doAddress we already try 3 times to get the edid data, so if the routine tells us that bus is not responding, it is mostly pointless to keep re-trying those attempts over and over again until we reach final number of retries.
This change should fix https://bugs.freedesktop.org/show_bug.cgi?id=41059 and improve overall edid detection timing by 10-30% in most cases, and by a much larger margin in case of phantom outputs (up to 30x in one worst case).
Timing results for i915-powered machines for 'time xrandr' command: Machine 1: from 0.840s to 0.290s Machine 2: from 0.315s to 0.280s Machine 3: from +/- 4s to 0.184s
Timing results for HD5770 with 'time xrandr' command: Machine 4: from 3.210s to 1.060s
Reviewed-by: Chris Wilson chris@hchris-wilson.co.uk Reviewed-by: Keith Packard keithp@keithp.com Tested-by: Sean Finney seanius@seanius.net Tested-by: Soren Hansen soren@linux2go.dk Tested-by: Hernando Torque sirius@sonnenkinder.org Tested-by: Mike Lothian mike@fireburn.co.uk Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41059 Signed-off-by: Eugeni Dodonov eugeni.dodonov@intel.com --- drivers/gpu/drm/drm_edid.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 7425e5c..1bca6d7 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -265,6 +265,11 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf, } }; ret = i2c_transfer(adapter, msgs, 2); + if (ret == -ENXIO) { + DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n", + adapter->name); + break; + } } while (ret != 2 && --retries);
return ret == 2 ? 0 : -1;