** Tags added: verification-done-focal
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https://bugs.launchpad.net/bugs/1949321
Title:
Fix System hangs on black screen when reboot
Status in HWE Next:
New
Status in linux package in Ubuntu:
In Progress
Status in linux-oem-5.10 package in Ubuntu:
Invalid
Status in linux-oem-5.14 package in Ubuntu:
Invalid
Status in linux source package in Focal:
New
Status in linux-oem-5.10 source package in Focal:
In Progress
Status in linux-oem-5.14 source package in Focal:
Fix Committed
Status in linux source package in Hirsute:
In Progress
Status in linux-oem-5.10 source package in Hirsute:
New
Status in linux-oem-5.14 source package in Hirsute:
New
Status in linux source package in Impish:
In Progress
Status in linux-oem-5.10 source package in Impish:
New
Status in linux-oem-5.14 source package in Impish:
New
Status in linux source package in Jammy:
In Progress
Status in linux-oem-5.10 source package in Jammy:
Invalid
Status in linux-oem-5.14 source package in Jammy:
Invalid
Bug description:
[Impact]
System hangs on black screen when reboot
[Fix]
Looks like our VBIOS/GOP generally fail to turn the DP dual mode adater
TMDS output buffers back on after a reboot. This leads to a black screen
after reboot if we turned the TMDS output buffers off prior to reboot.
And if i915 decides to do a fastboot the black screen will persist even
after i915 takes over.
Apparently this has been a problem ever since commit b2ccb822d376
("drm/i915:Enable/disable TMDS output buffers in DP++ adaptor as needed") if
one rebooted while the display was turned off. And things became worse with
commit fe0f1e3bfdfe ("drm/i915: Shut down displays gracefully on reboot") since
now we always turn the display off before a reboot.
This was reported on a RKL, but I confirmed the same behaviour on my
SNB as well. So looks pretty universal.
Let's fix this by explicitly turning the TMDS output buffers back on
in the encoder->shutdown() hook. Note that this gets called after irqs
have been disabled, so the i2c communication with the DP dual mode
adapter has to be performed via polling (which the gmbus code is
perfectly happy to do for us).
We also need a bit of care in handling DDI encoders which may or may
not be set up for HDMI output. Specifically ddc_pin will not be
populated for a DP only DDI encoder, in which case we don't want to
call intel_gmbus_get_adapter(). We can handle that by simply doing
the dual mode adapter type check before calling
intel_gmbus_get_adapter().
Ref: https://patchwork.freedesktop.org/series/96433/
[Test]
1. install kernel
2. reboot
3. check the monitor works well.
[Regression Potential]
Medium, patch has sent to patchwork but may have a upgraded version in the
furtue.
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