drm/i915: Restore GMBUS operation after a failed bit-banging fallback
When the GMBUS based i2c transfer times out, we try to fall back to bit-banging and retry the operation that way. However if the bit-banging attempt also fails, we should probably go back to the GMBUS method for the next attempt. Maybe there simply wasn't anyone one the bus at this time. There's also a bit of a mess going on with the force_bit handling. It's supposed to be a ref count actually, and it is as far as intel_gmbus_force_bit() is concerned. But it's treated as just a flag by the timeout based bit-banging fallback. I suppose that's fine since we should never end up in the timeout fallback case if force_bit was already non-zero. However now that we want to restore things back to where they were after the bit-banging attempt failed, we're going to have to do things a bit differently to avoid clobbering the force_bit count as set up by intel_gmbus_force_bit(). So let's dedicate the high bit as a flag for the low level timeout based fallback and treat the rest of the bits as a ref count just as before. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1457366220-29409-4-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>
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