linux-kernel - [PATCH 1/1] drm/i915: ensure i2c adapter is all set before adding it

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Message-Id: <b6dc8317cdc108b22f90453b3d6f7475a620d96c.1344867962.git.jani.nikula@intel.com>
Date:	Mon, 13 Aug 2012 17:33:02 +0300
From:	Jani Nikula <jani.nikula@...el.com>
To:	ionic@...ic.de
Cc:	daniel@...ll.ch, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, jani.nikula@...el.com
Subject: [PATCH 1/1] drm/i915: ensure i2c adapter is all set before adding it

i2c_add_adapter() may do i2c transfers on the bus to detect supported
devices. Therefore the adapter needs to be all set before adding it. This
was not the case for the bit-banging fallback, resulting in an oops if the
device detection GMBUS transfers timed out. Fix the issue by calling
i2c_add_adapter() only after intel_gpio_setup().

LKML-Reference: <5021F00B.7000503@...ic.de>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
---
 drivers/gpu/drm/i915/intel_i2c.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 1991a44..a23ba84f 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -486,9 +486,6 @@ int intel_setup_gmbus(struct drm_device *dev)
 		bus->dev_priv = dev_priv;
 
 		bus->adapter.algo = &gmbus_algorithm;
-		ret = i2c_add_adapter(&bus->adapter);
-		if (ret)
-			goto err;
 
 		/* By default use a conservative clock rate */
 		bus->reg0 = port | GMBUS_RATE_100KHZ;
@@ -498,6 +495,10 @@ int intel_setup_gmbus(struct drm_device *dev)
 			bus->force_bit = true;
 
 		intel_gpio_setup(bus, port);
+
+		ret = i2c_add_adapter(&bus->adapter);
+		if (ret)
+			goto err;
 	}
 
 	intel_i2c_reset(dev_priv->dev);
-- 
1.7.9.5

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