[Intel-gfx] [PATCH 1/4] drm/i915: Actually retry with bit-banging after GMBUS timeout

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

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 at intel.com>
Cc: drm-intel-fixes at lists.freedesktop.org
Fixes: bffce907d640 ("drm/i915: abstract i2c bit banging fallback in gmbus xfer")
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_i2c.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index deb8282c26d8..52fbe530fc9e 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -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;
 
-- 
2.4.10