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drm/i915: Actually retry with bit-banging after GMBUS timeout 

After the GMBUS transfer times out, we set force_bit=1 and
return -EAGAIN expecting the i2c core to call the .master_xfer
hook again so that we will retry the same transfer via bit-banging.
This is in case the gmbus hardware is somehow faulty.

Unfortunately we left adapter->retries to 0, meaning the i2c core
didn't actually do the retry. Let's tell the core we want one retry
when we return -EAGAIN.

Note that i2c-algo-bit also uses this retry count for some internal
retries, so we'll end up increasing those a bit as well.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: drm-intel-fixes@lists.freedesktop.org
Fixes: bffce907d6 ("drm/i915: abstract i2c bit banging fallback in gmbus xfer")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457366220-29409-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 8b1f165a4a)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
hifive-unleashed-5.1
Ville Syrjälä 2016-03-07 17:56:57 +02:00 committed by Jani Nikula
parent 2f791908a7
commit 0bbca274a3
1 changed files with 6 additions and 0 deletions
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6
drivers/gpu/drm/i915/intel_i2c.c
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@ -664,6 +664,12 @@ int intel_setup_gmbus(struct drm_device *dev)
bus->adapter.algo = &gmbus_algorithm;
/*
* We wish to retry with bit banging
* after a timed out GMBUS attempt.
*/
bus->adapter.retries = 1;
/* By default use a conservative clock rate */
bus->reg0 = pin | GMBUS_RATE_100KHZ;