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@ionic.de>
Tested-by: Mihai Moldovan <ionic@ionic.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index d79500bc1ce5..b9755f6378d8 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);