Get the extended DPCD according to the related field in the DPCD registers.

[koba]

[Impact]
Connect the 4K@60Hz monitor on WD19, the monitor can't light.

[Fix]
As per DP spec, at first check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT.
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1, read the DP_DP13_DPCD_REV to get the faster capability. If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0, read DP_DPCD_REV.

[Test]
With the patches, connect 4K@60Hz monitor on WD19, the machine can output the video to the monitor and the monitor can light.

[Regression]
low, Just get one more DPCD from the extended register, compare them and get the faster one.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1893752

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-oem-5.6 - 5.6.0-1031.32

---------------
linux-oem-5.6 (5.6.0-1031.32) focal; urgency=medium

  * Packaging resync (LP: #1786013)
    - update dkms package versions

  * CVE-2020-16119
    - SAUCE: dccp: avoid double free of ccid on child socket

  * CVE-2020-16120
    - ovl: pass correct flags for opening real directory
    - ovl: switch to mounter creds in readdir
    - ovl: verify permissions in ovl_path_open()
    - ovl: call secutiry hook in ovl_real_ioctl()
    - ovl: check permission to open real file

linux-oem-5.6 (5.6.0-1030.30) focal; urgency=medium

  * focal/linux-oem-5.6: 5.6.0-1030.30 -proposed tracker (LP: #1898714)

  * Fix broken e1000e device after S3 (LP: #1897755)
    - SAUCE: e1000e: Increase polling timeout on MDIC ready bit

  * Fix headset jack detection on Dell UFF desktops (LP: #1897508)
    - Revert "ALSA: hda: call runtime_allow() for all hda controllers"

  * [SRU][OEM-5.6]Fix AMD system hang after re-plugin USBC-DP dongle
    (LP: #1896716)
    - drm/amd/display: Move USB-C workaround to after parameter variables are set

  * alsa/hda: mic doesn't work on a HP AIO machine (LP: #1897694)
    - SAUCE: ALSA: hda/realtek - set mic to auto detect on a HP AIO machine

  * CVE-2020-26088
    - net/nfc/rawsock.c: add CAP_NET_RAW check.

  * HP Zbook Studio G7 boots into corrupted screen with PSR featured panel
    (LP: #1897501)
    - SAUCE: drm/i915/psr: allow overriding PSR disable param by quirk
    - SAUCE: drm/dp: add DP_QUIRK_FORCE_PSR_CHIP_DEFAULT quirk to CMN prod-ID
      19-15

linux-oem-5.6 (5.6.0-1029.29) focal; urgency=medium

  * focal/linux-oem-5.6: 5.6.0-1029.29 -proposed tracker (LP: #1895982)

  * linux-libc-dev in proposed cause seccomp_bpf from seccomp in
    ubuntu_kernel_selftests to fail on F-oem-5.6 (LP: #1896008)
    - seccomp: Fix ioctl number for SECCOMP_IOCTL_NOTIF_ID_VALID

  * Enable LTR for endpoints behind VMD (LP: #1896598)
    - SAUCE: PCI/ASPM: Enable LTR for endpoints behind VMD

  * CVE-2020-14385
    - xfs: fix boundary test in xfs_attr_shortform_verify

  * Fix non-working NVMe after S3 (LP: #1895718)
    - SAUCE: PCI: Enable ACS quirk on CML root port

  * CVE-2020-12655
    - xfs: add agf freeblocks verify in xfs_agf_verify

  * Thunderbolt3 daisy chain sometimes doesn't work (LP: #1895606)
    - thunderbolt: Retry DROM read once if parsing fails

  * CVE-2020-12656
    - sunrpc: svcauth_gss_register_pseudoflavor must reject duplicate
      registrations.
    - sunrpc: clean up properly in gss_mech_unregister()

  * CVE-2020-15393
    - usb: usbtest: fix missing kfree(dev->buf) in usbtest_disconnect

  * CVE-2020-12771
    - bcache: fix potential deadlock problem in btree_gc_coalesce

  * CVE-2020-15780
    - ACPI: configfs: Disallow loading ACPI tables when locked down

  * CVE-2020-16166
    - random32: update the net random state on interrupt and activity

  * Get the extended DPCD according to the related field in the DPCD registers.
    (LP: #1893752)
    - drm: move DP_MAX_DOWNSTREAM_PORTS from i915 to drm core
    - drm/i915/dp: Extract drm_dp_read_dpcd_caps()
    - SAUCE: drm/dp_mst: Retrieve extended DPCD caps for topology manager
...