drm/i915/crt: Remove 0xa0 probe for VGA
This is a moral revert of 6ec3d0c0e9
.
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 <sitsofe@yahoo.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35904
Reported-and-tested-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=32612
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
parent
7f58aabc36
commit
0de009c900
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@ -269,21 +269,6 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
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return ret;
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}
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static bool intel_crt_ddc_probe(struct drm_i915_private *dev_priv, int ddc_bus)
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{
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u8 buf;
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struct i2c_msg msgs[] = {
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{
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.addr = 0xA0,
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.flags = 0,
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.len = 1,
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.buf = &buf,
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},
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};
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/* DDC monitor detect: Does it ACK a write to 0xA0? */
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return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 1) == 1;
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}
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static bool intel_crt_detect_ddc(struct drm_connector *connector)
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{
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struct intel_crt *crt = intel_attached_crt(connector);
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@ -293,11 +278,6 @@ static bool intel_crt_detect_ddc(struct drm_connector *connector)
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if (crt->base.type != INTEL_OUTPUT_ANALOG)
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return false;
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if (intel_crt_ddc_probe(dev_priv, dev_priv->crt_ddc_pin)) {
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DRM_DEBUG_KMS("CRT detected via DDC:0xa0\n");
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return true;
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}
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if (intel_ddc_probe(&crt->base, dev_priv->crt_ddc_pin)) {
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struct edid *edid;
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bool is_digital = false;
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