[bionic] hts221 sensor stops working after resume from S3/S4

[Shrirang Bagul]

[SRU Justification]

[Impact]

Dell Edge 300x IoT Gateways have a relative humidity sensor hts221. The sensor stops working (and reports stale values) after the system resumes from suspend-to-ram/suspend-to-disk PM states.

== Fix ==
AV_CONF register (RH & TEMP. oversampling ratio's) and CTRL1 register (ODR & BDU settings) values are lost after suspend.

While the change in AV_CONF updates the sensor resolution modes (overriding the user configuration before the device went to suspend); loss of the contents of the CTRL1 register leads to failure in reading sensor

This patch restores the AV_CONF & CTRL1 registers after

Already submitted upstream for both 4.17.y and 4.14.y (LTS) for review:
4.17.y: https://marc.info/?t=152455871600007&r=1&w=2
4.14.y: https://marc.info/?t=152506242000001&r=1&w=2

However, the issue is only affecting the Dell GW and not ST micro devel. boards.

== Risk of Regression ==
Low.Tthe bug affects only the Dell GW and the patch is being carried in linux-oem (4.15.y) since last 2 years without any regression.

linux-oem buglink: https://bugs.launchpad.net/bugs/1769658

This bug is for tracking purposes only, please don't triage.

[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 1863732

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-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

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 - 4.15.0-96.97

---------------
linux (4.15.0-96.97) bionic; urgency=medium

  * CVE-2020-8834
    - KVM: PPC: Book3S HV: Factor fake-suspend handling out of
      kvmppc_save/restore_tm
    - KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file
    - KVM: PPC: Book3S PR: Add guest MSR parameter for
      kvmppc_save_tm()/kvmppc_restore_tm()

linux (4.15.0-94.95) bionic; urgency=medium

  * bionic/linux: 4.15.0-94.95 -proposed tracker (LP: #1868984)

  * Missing wireless network interface after kernel 5.3.0-43 upgrade with eoan
    (LP: #1868442)
    - iwlwifi: mvm: Do not require PHY_SKU NVM section for 3168 devices

linux (4.15.0-93.94) bionic; urgency=medium

  * bionic/linux: 4.15.0-93.94 -proposed tracker (LP: #1868764)

  * quotactl04 from ubuntu_ltp_syscalls failed with B (LP: #1868665)
    - ext4: fix mount failure with quota configured as module

linux (4.15.0-92.93) bionic; urgency=medium

  * bionic/linux: 4.15.0-92.93 -proposed tracker (LP: #1867272)

  * Packaging resync (LP: #1786013)
    - [Packaging] resync getabis
    - [Packaging] update helper scripts

  * Introduce the new NVIDIA 440 series, and add 5.4 Linux compatibility to the
    340 and 390 series (LP: #1854485)
    - [Packaging] NVIDIA -- add support for the 435 and the 440 series

  * Stop using get_scalar_status command in Dell AIO uart backlight driver
    (LP: #1865402)
    - SAUCE: platform/x86: dell-uart-backlight: add get_display_mode command

  * Bionic update: upstream stable patchset 2020-03-12 (LP: #1867194)
    - RDMA/core: Fix locking in ib_uverbs_event_read
    - gpio: zynq: Report gpio direction at boot
    - arm64: ptrace: nofpsimd: Fail FP/SIMD regset operations
    - KVM: arm: Fix DFSR setting for non-LPAE aarch32 guests
    - KVM: arm: Make inject_abt32() inject an external abort instead
    - mtd: onenand_base: Adjust indentation in onenand_read_ops_nolock
    - mtd: sharpslpart: Fix unsigned comparison to zero
    - padata: fix null pointer deref of pd->pinst
    - Input: synaptics - switch T470s to RMI4 by default
    - Input: synaptics - enable SMBus on ThinkPad L470
    - Input: synaptics - remove the LEN0049 dmi id from topbuttonpad list
    - ALSA: hda/realtek - Fix silent output on MSI-GL73
    - ALSA: usb-audio: Apply sample rate quirk for Audioengine D1
    - arm64: cpufeature: Set the FP/SIMD compat HWCAP bits properly
    - ALSA: usb-audio: sound: usb: usb true/false for bool return type
    - ext4: don't assume that mmp_nodename/bdevname have NUL
    - ext4: fix support for inode sizes > 1024 bytes
    - ext4: fix checksum errors with indexed dirs
    - ext4: add cond_resched() to ext4_protect_reserved_inode
    - ext4: improve explanation of a mount failure caused by a misconfigured
      kernel
    - Btrfs: fix race between using extent maps and merging them
    - btrfs: ref-verify: fix memory leaks
    - btrfs: print message when tree-log replay starts
    - btrfs: log message when rw remount is attempted with unclean tree-log
    - arm64: ssbs: Fix context-switch when SSBS is present on all CPUs
    - perf/x86/amd: Add missing L2 misses event spec to AMD Family 17h's ev...