From 0de009c900e7ebd21097797f723a40813e953879 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 5 Apr 2011 16:04:39 +0100 Subject: 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: https://bugs.freedesktop.org/show_bug.cgi?id=35904 Reported-and-tested-by: Riccardo Magliocchetti Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=32612 Signed-off-by: Chris Wilson Acked-by: Dave Airlie Signed-off-by: Keith Packard --- drivers/gpu/drm/i915/intel_crt.c | 20 -------------------- 1 file changed, 20 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c index 8342259f3160..d03fc05b39c0 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; -- cgit v1.2.1 From a6737ad15b4acf88bbf7753e929faf215adeaa3a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 5 Apr 2011 16:04:40 +0100 Subject: drm/i915/lvds: Remove 0xa0 DDC probe for LVDS This is a revert of 428d2e828c0a68206e5158a42451487601dc9194. This is broken in the same manner as for VGA: trying to write to an invalid address on the (currently 7-bit) i2c bus. One notable failure appears to be for MacBooks. The scary part was that it gave the appearance of working (i.e. reporting the absence of the panel) on various all-in-one machines with ghost LVDS panels and not failing for laptops. Signed-off-by: Chris Wilson Acked-by: Dave Airlie Signed-off-by: Keith Packard --- drivers/gpu/drm/i915/intel_lvds.c | 24 ------------------------ 1 file changed, 24 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c index 86cd30bcb619..a562bd2648c7 100644 --- a/drivers/gpu/drm/i915/intel_lvds.c +++ b/drivers/gpu/drm/i915/intel_lvds.c @@ -829,25 +829,6 @@ static bool lvds_is_present_in_vbt(struct drm_device *dev, return false; } -static bool intel_lvds_ddc_probe(struct drm_device *dev, u8 pin) -{ - struct drm_i915_private *dev_priv = dev->dev_private; - u8 buf = 0; - struct i2c_msg msgs[] = { - { - .addr = 0xA0, - .flags = 0, - .len = 1, - .buf = &buf, - }, - }; - struct i2c_adapter *i2c = &dev_priv->gmbus[pin].adapter; - /* XXX this only appears to work when using GMBUS */ - if (intel_gmbus_is_forced_bit(i2c)) - return true; - return i2c_transfer(i2c, msgs, 1) == 1; -} - /** * intel_lvds_init - setup LVDS connectors on this device * @dev: drm device @@ -888,11 +869,6 @@ bool intel_lvds_init(struct drm_device *dev) } } - if (!intel_lvds_ddc_probe(dev, pin)) { - DRM_DEBUG_KMS("LVDS did not respond to DDC probe\n"); - return false; - } - intel_lvds = kzalloc(sizeof(struct intel_lvds), GFP_KERNEL); if (!intel_lvds) { return false; -- cgit v1.2.1