lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

drm/i915: Fix DDC on some systems by clearing BIOS GMBUS setup.

Browse Source 
This is a sync of a fix I made in the old UMS code.  If the BIOS uses
the GMBUS and doesn't clear that setup, then our bit-banging I2C can
fail, leading to monitors not being detected.

Signed-off-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Eric Anholt
2009-12-01 11:56:30 -08:00
parent d09c23de9f
commit f0217c42c9
4 changed files with 39 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/gpu/drm/i915/intel_i2c.c
View File

@@ -118,6 +118,23 @@ static void set_data(void *data, int state_high)
udelay(I2C_RISEFALL_TIME); /* wait for the line to change state */
}
/* Clears the GMBUS setup. Our driver doesn't make use of the GMBUS I2C
* engine, but if the BIOS leaves it enabled, then that can break our use
* of the bit-banging I2C interfaces. This is notably the case with the
* Mac Mini in EFI mode.
*/
void
intel_i2c_reset_gmbus(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
if (IS_IGDNG(dev)) {
I915_WRITE(PCH_GMBUS0, 0);
} else {
I915_WRITE(GMBUS0, 0);
}
}
/**
* intel_i2c_create - instantiate an Intel i2c bus using the specified GPIO reg
* @dev: DRM device
@@ -168,6 +185,8 @@ struct i2c_adapter *intel_i2c_create(struct drm_device *dev, const u32 reg,
if(i2c_bit_add_bus(&chan->adapter))
goto out_free;
intel_i2c_reset_gmbus(dev);
/* JJJ: raise SCL and SDA? */
intel_i2c_quirk_set(dev, true);
set_data(chan, 1);