diff options
authorChris Wilson <>2011-04-05 16:04:39 +0100
committerKeith Packard <>2011-04-05 09:05:34 -0700
commit0de009c900e7ebd21097797f723a40813e953879 (patch)
parent7f58aabc369014fda3a4a33604ba0a1b63b941ac (diff)
drm/i915/crt: Remove 0xa0 probe for VGA
This is a moral revert of 6ec3d0c0e9c0c605696e91048eebaca7b0c36695. Following the fix to reset the GMBUS controller after a NAK, we finally utilize the 0xa0 probe for a CRT connection. And discover that the code is broken. Shock. There are a number of issues, but following a key insight from Dave Airlie, that 0xA0 is an invalid address on a 7-bit bus (though not if we were to enable 10-bit addressing), and would look like the EDID port 0x50, it is possible to see where the confusion starts. In short, a write to 0xA0 is accepted by the GMBUS controller which we interpreted as meaning the existence of a connection (a slave on the other end of the wire ACKing the write). That was false. During testing with a broken GMBUS implementation, which never reset an earlier NAK, this test always reported a NAK and so we proceeded on to the next test. Reported-and-tested-by: Sitsofe Wheeler <> Bugzilla: Reported-and-tested-by: Riccardo Magliocchetti <> Bugzilla: Signed-off-by: Chris Wilson <> Acked-by: Dave Airlie <> Signed-off-by: Keith Packard <>
1 files changed, 0 insertions, 20 deletions
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 8342259f316..d03fc05b39c 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -269,21 +269,6 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
return ret;
-static bool intel_crt_ddc_probe(struct drm_i915_private *dev_priv, int ddc_bus)
- u8 buf;
- struct i2c_msg msgs[] = {
- {
- .addr = 0xA0,
- .flags = 0,
- .len = 1,
- .buf = &buf,
- },
- };
- /* DDC monitor detect: Does it ACK a write to 0xA0? */
- return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 1) == 1;
static bool intel_crt_detect_ddc(struct drm_connector *connector)
struct intel_crt *crt = intel_attached_crt(connector);
@@ -293,11 +278,6 @@ static bool intel_crt_detect_ddc(struct drm_connector *connector)
if (crt->base.type != INTEL_OUTPUT_ANALOG)
return false;
- if (intel_crt_ddc_probe(dev_priv, dev_priv->crt_ddc_pin)) {
- DRM_DEBUG_KMS("CRT detected via DDC:0xa0\n");
- return true;
- }
if (intel_ddc_probe(&crt->base, dev_priv->crt_ddc_pin)) {
struct edid *edid;
bool is_digital = false;