From 0bbca274a31c2366414d8d3f95e03d1c4674d93f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Mon, 7 Mar 2016 17:56:57 +0200
Subject: [PATCH] drm/i915: Actually retry with bit-banging after GMBUS timeout
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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: bffce907d640 ("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 8b1f165a4a8f64c28cf42d10e1f4d3b451dedc51)
Signed-off-by: Jani Nikula <jani.nikula@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 deb8282c26d83..52fbe530fc9ea 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;
--
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