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Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted

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  Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted /dev/fra <devfra@inventati.org> - 2020-10-10 16:40 +0200
    Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted /dev/fra <devfra@inventati.org> - 2020-11-07 23:30 +0100
    Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted Avinash Sonawane <rootkea@gmail.com> - 2020-11-28 07:30 +0100
    Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted William Sones <william.r.sones@googlemail.com> - 2021-01-15 19:00 +0100

#68345 — Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted

Package: src:linux
Version: 5.8.10-1~bpo10+1
Severity: normal
File: linux-image-5.8

Dear Maintainer,

On the ASUS T100TA convertible laptop [1], and probably on similar
devices with the same Intel Bay Trail chipset as well, the screen
backlight cannot be adjusted and it is set to the maximum brightness. It
looks like the problem is caused by a failure in controlling the PMIC
'Crystal Cove' of the Intel Bay Trail chipsets family.

Relevant messages from journalctl:
> oct 10 15:26:51 asus kernel: fb0: switching to inteldrmfb from EFI VGA
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: vgaarb: deactivate vga console
> oct 10 15:26:51 asus kernel: [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: cannot find GPIO chip gpio_crystalcove, deferring
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: [drm] *ERROR* Failed to own gpio for panel control
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: [drm] *ERROR* Failed to get the PMIC PWM chip
> oct 10 15:26:51 asus kernel: [drm] Initialized i915 1.6.0 20200515 for 0000:00:02.0 on minor 0
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: [drm] HDaudio controller not detected, using LPE audio instead
> oct 10 15:26:51 asus kernel: fbcon: i915drmfb (fb0) is primary device
> oct 10 15:26:51 asus kernel: i915 0000:00:02.0: fb0: i915drmfb frame buffer device

The problem is present in Debian stable using the default Linux kernel
4.9 and the kernel 5.8 from the backports repositories.

I found two similar bug reports from other sources:
- Backlight init fails on Surface 3 if module load order is wrong [2]
- chromeos-5.4: backlight not adjustable #23 [3]

If I read them correctly, it appears there might be already some
upstream patches addressing this problem. Could you please have a look
into it?

Cheers

[1] https://wiki.debian.org/InstallingDebianOn/Asus/T100TA
[2] https://gitlab.freedesktop.org/drm/intel/-/issues/26
[3] https://github.com/kitakar5525/chromeos-kernel-linux-surface/issues/23


-- Package-specific info:
** Version:
Linux version 5.8.0-0.bpo.2-amd64 (debian-kernel@lists.debian.org) (gcc-8 (Debian 8.3.0-6) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #1 SMP Debian 5.8.10-1~bpo10+1 (2020-09-26)

** Command line:
BOOT_IMAGE=/vmlinuz-5.8.0-0.bpo.2-amd64 root=/dev/mapper/asus--vg-root ro quiet

** Tainted: W (512)
 * kernel issued warning

** Kernel log:
[   29.717389] Bluetooth: HCI UART protocol Three-wire (H5) registered
[   29.717499] Bluetooth: HCI UART protocol Intel registered
[   29.717660] Bluetooth: HCI UART protocol Broadcom registered
[   29.717682] Bluetooth: HCI UART protocol QCA registered
[   29.717684] Bluetooth: HCI UART protocol AG6XX registered
[   29.717705] Bluetooth: HCI UART protocol Marvell registered
[   29.737331] hci_uart_bcm serial0-0: ACPI Interrupt resource is active-high, this is usually wrong, treating the IRQ as active-low
[   29.737552] hci_uart_bcm serial0-0: supply vbat not found, using dummy regulator
[   29.737588] hci_uart_bcm serial0-0: supply vddio not found, using dummy regulator
[   29.809317] input: PC Speaker as /devices/platform/pcspkr/input/input19
[   29.861292] i2c i2c-4: Added multiplexed i2c bus 14
[   29.877515] EFI Variables Facility v0.08 2004-May-17
[   29.878530] ak8975 14-000c: mounting matrix not found: using identity...
[   29.878540] ak8975 14-000c: supply vdd not found, using dummy regulator
[   29.878585] ak8975 14-000c: supply vid not found, using dummy regulator
[   29.918897] pstore: Using crash dump compression: deflate
[   29.935053] pstore: Registered efi as persistent store backend
[   30.114856] cfg80211: Loading compiled-in X.509 certificates for regulatory database
[   30.115501] cfg80211: Loaded X.509 cert 'benh@debian.org: 577e021cb980e0e820821ba7b54b4961b8b4fadf'
[   30.116078] cfg80211: Loaded X.509 cert 'romain.perier@gmail.com: 3abbc6ec146e09d1b6016ab9d6cf71dd233f0328'
[   30.116652] cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
[   30.134195] platform regulatory.0: firmware: direct-loading firmware regulatory.db
[   30.168580] platform regulatory.0: firmware: direct-loading firmware regulatory.db.p7s
[   30.284604] Bluetooth: hci0: BCM: chip id 84
[   30.301725] Bluetooth: hci0: BCM: features 0x0f
[   30.319706] Bluetooth: hci0: BCM4324B3
[   30.319717] Bluetooth: hci0: BCM4324B3 (002.004.006) build 0000
[   30.322002] bluetooth hci0: firmware: failed to load brcm/BCM4324B3.hcd (-2)
[   30.322098] firmware_class: See https://wiki.debian.org/Firmware for information about missing firmware
[   30.322244] bluetooth hci0: firmware: failed to load brcm/BCM.hcd (-2)
[   30.322320] Bluetooth: hci0: BCM: firmware Patch file not found, tried:
[   30.322394] Bluetooth: hci0: BCM: 'brcm/BCM4324B3.hcd'
[   30.322452] Bluetooth: hci0: BCM: 'brcm/BCM.hcd'
[   30.352555] intel_rapl_common: Found RAPL domain package
[   30.352559] intel_rapl_common: Found RAPL domain core
[   30.383338] mmc1: queuing unknown CIS tuple 0x80 (2 bytes)
[   30.386482] input: gpio-keys as /devices/platform/INTCFD9:00/gpio-keys.1.auto/input/input20
[   30.389179] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
[   30.390728] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
[   30.393499] mmc1: queuing unknown CIS tuple 0x80 (7 bytes)
[   30.515827] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43241b4-sdio for chip BCM4324/5
[   30.515947] usbcore: registered new interface driver brcmfmac
[   30.524231] brcmfmac mmc1:0001:1: firmware: direct-loading firmware brcm/brcmfmac43241b4-sdio.bin
[   30.524290] brcmfmac mmc1:0001:1: firmware: failed to load brcm/brcmfmac43241b4-sdio.ASUSTeK COMPUTER INC.-T100TA.txt (-2)
[   30.524427] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43241b4-sdio.ASUSTeK COMPUTER INC.-T100TA.txt failed with error -2
[   30.528984] brcmfmac mmc1:0001:1: firmware: direct-loading firmware brcm/brcmfmac43241b4-sdio.txt
[   30.563863] bytcr_rt5640 bytcr_rt5640: quirk IN1_MAP enabled
[   30.563868] bytcr_rt5640 bytcr_rt5640: quirk realtek,jack-detect-source 3
[   30.563871] bytcr_rt5640 bytcr_rt5640: quirk realtek,over-current-threshold-microamp 2000
[   30.563873] bytcr_rt5640 bytcr_rt5640: quirk realtek,over-current-scale-factor 1
[   30.563876] bytcr_rt5640 bytcr_rt5640: quirk MCLK_EN enabled
[   30.619362] bytcr_rt5640 bytcr_rt5640: snd-soc-dummy-dai <-> media-cpu-dai mapping ok
[   30.619935] bytcr_rt5640 bytcr_rt5640: snd-soc-dummy-dai <-> deepbuffer-cpu-dai mapping ok
[   30.641527] bytcr_rt5640 bytcr_rt5640: rt5640-aif1 <-> ssp2-port mapping ok
[   30.648684] input: bytcr-rt5640 Headset as /devices/platform/80860F28:00/bytcr_rt5640/sound/card1/input21
[   30.708603] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43241b4-sdio for chip BCM4324/5
[   30.708670] brcmfmac mmc1:0001:1: firmware: failed to load brcm/brcmfmac43241b4-sdio.clm_blob (-2)
[   30.708786] brcmfmac: brcmf_c_process_clm_blob: no clm_blob available (err=-2), device may have limited channels available
[   30.710216] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4324/5 wl0: Jul 17 2013 07:36:07 version 6.10.197.71 (r412987) FWID 01-882d2634
[   30.869962] EXT4-fs (mmcblk2p2): mounting ext2 file system using the ext4 subsystem
[   30.874376] EXT4-fs (mmcblk2p2): mounted filesystem without journal. Opts: (null)
[   30.874399] ext2 filesystem being mounted at /boot supports timestamps until 2038 (0x7fffffff)
[   30.905219] Adding 1982460k swap on /dev/mapper/asus--vg-swap_1.  Priority:-2 extents:1 across:1982460k SSFS
[   40.276845] BTRFS: device fsid 8706c28b-48f2-4fe0-85b3-7406de75e896 devid 1 transid 3937 /dev/dm-3 scanned by systemd-udevd (715)
[   40.370927] BTRFS info (device dm-3): use zstd compression, level 3
[   40.370931] BTRFS info (device dm-3): disk space caching is enabled
[   40.370933] BTRFS info (device dm-3): has skinny extents
[   40.437324] BTRFS info (device dm-3): enabling ssd optimizations
[   40.609657] audit: type=1400 audit(1602336423.023:2): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/sbin/haveged" pid=756 comm="apparmor_parser"
[   40.610372] audit: type=1400 audit(1602336423.023:3): apparmor="STATUS" operation="profile_load" profile="unconfined" name="libreoffice-senddoc" pid=757 comm="apparmor_parser"
[   40.614667] audit: type=1400 audit(1602336423.027:4): apparmor="STATUS" operation="profile_load" profile="unconfined" name="libreoffice-oopslash" pid=755 comm="apparmor_parser"
[   40.623492] audit: type=1400 audit(1602336423.035:5): apparmor="STATUS" operation="profile_load" profile="unconfined" name="libreoffice-xpdfimport" pid=759 comm="apparmor_parser"
[   40.624980] audit: type=1400 audit(1602336423.035:6): apparmor="STATUS" operation="profile_load" profile="unconfined" name="firejail-default" pid=760 comm="apparmor_parser"
[   40.627843] audit: type=1400 audit(1602336423.039:7): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/sbin/cups-browsed" pid=758 comm="apparmor_parser"
[   40.631711] audit: type=1400 audit(1602336423.043:8): apparmor="STATUS" operation="profile_load" profile="unconfined" name="nvidia_modprobe" pid=761 comm="apparmor_parser"
[   40.631721] audit: type=1400 audit(1602336423.043:9): apparmor="STATUS" operation="profile_load" profile="unconfined" name="nvidia_modprobe//kmod" pid=761 comm="apparmor_parser"
[   40.640603] audit: type=1400 audit(1602336423.051:10): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/bin/man" pid=763 comm="apparmor_parser"
[   40.640616] audit: type=1400 audit(1602336423.051:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="man_filter" pid=763 comm="apparmor_parser"
[   41.222933] zram: Added device: zram0
[   41.223307] zram: Added device: zram1
[   41.224858] zram: Added device: zram2
[   41.225462] zram: Added device: zram3
[   41.240255] zram0: detected capacity change from 0 to 67108864
[   41.281158] Adding 65532k swap on /dev/zram0.  Priority:100 extents:1 across:65532k SSFS
[   41.282317] zram1: detected capacity change from 0 to 67108864
[   41.317537] Adding 65532k swap on /dev/zram1.  Priority:100 extents:1 across:65532k SSFS
[   41.319534] zram2: detected capacity change from 0 to 67108864
[   41.357203] Adding 65532k swap on /dev/zram2.  Priority:100 extents:1 across:65532k SSFS
[   41.358349] zram3: detected capacity change from 0 to 67108864
[   41.401206] Adding 65532k swap on /dev/zram3.  Priority:100 extents:1 across:65532k SSFS
[   41.451901] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[   41.451905] Bluetooth: BNEP filters: protocol multicast
[   41.451914] Bluetooth: BNEP socket layer initialized
[   42.646140] broken atomic modeset userspace detected, disabling atomic
[   51.217174] intel_sst_acpi 80860F28:00: FW Version 01.0c.00.01
[   51.665189] Bluetooth: RFCOMM TTY layer initialized
[   51.665201] Bluetooth: RFCOMM socket layer initialized
[   51.665220] Bluetooth: RFCOMM ver 1.11
[ 1056.034607] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 1056.289680] tun: Universal TUN/TAP device driver, 1.6

** Model information
sys_vendor: ASUSTeK COMPUTER INC.
product_name: T100TA
product_version: 1.0
chassis_vendor: ASUSTeK COMPUTER INC.
chassis_version: 1.0
bios_vendor: American Megatrends Inc.
bios_version: T100TA.314
board_vendor: ASUSTeK COMPUTER INC.
board_name: T100TA
board_version: 1.0

** Loaded modules:
tun
rfcomm
bnep
zram
zsmalloc
nls_ascii
nls_cp437
vfat
fat
snd_soc_sst_bytcr_rt5640
gpio_keys
intel_soc_dts_thermal
intel_powerclamp
intel_rapl_msr
coretemp
kvm_intel
brcmfmac
kvm
brcmutil
cfg80211
irqbypass
efi_pstore
intel_cstate
ak8975
efivars
pcspkr
joydev
hci_uart
sg
btqca
hid_multitouch
btrtl
snd_soc_rt5670
btbcm
snd_soc_rt5651
btintel
bluetooth
snd_soc_rt5645
snd_intel_sst_acpi
iTCO_wdt
snd_intel_sst_core
intel_pmc_bxt
iTCO_vendor_support
snd_hdmi_lpe_audio
snd_soc_sst_atom_hifi2_platform
jitterentropy_rng
snd_soc_rt5640
watchdog
snd_soc_acpi_intel_match
tpm_crb
snd_soc_acpi
snd_soc_rl6231
tpm_tis
inv_mpu6050_i2c
tpm_tis_core
snd_soc_core
tpm
drbg
inv_mpu6050
evdev
snd_compress
industrialio_triggered_buffer
rng_core
kfifo_buf
snd_pcm
ansi_cprng
soc_button_array
processor_thermal_device
dptf_power
int3406_thermal
intel_rapl_common
snd_timer
int3400_thermal
int3403_thermal
intel_soc_dts_iosf
int340x_thermal_zone
acpi_thermal_rel
industrialio
ecdh_generic
intel_int0002_vgpio
ecc
snd
asus_wireless
acpi_pad
i2c_mux
ac
soundcore
pwm_lpss_platform
pwm_lpss
parport_pc
ppdev
lp
parport
efivarfs
ip_tables
x_tables
autofs4
ext4
crc16
mbcache
jbd2
btrfs
blake2b_generic
xor
zstd_decompress
zstd_compress
raid6_pq
libcrc32c
crc32c_generic
algif_skcipher
af_alg
sd_mod
t10_pi
crc_t10dif
crct10dif_generic
hid_asus
asus_wmi
sparse_keymap
rfkill
dm_crypt
dm_mod
usbhid
uas
usb_storage
scsi_mod
hid_generic
i915
crct10dif_pclmul
crct10dif_common
crc32_pclmul
crc32c_intel
ghash_clmulni_intel
mmc_block
aesni_intel
i2c_algo_bit
drm_kms_helper
xhci_pci
xhci_hcd
cec
drm
libaes
crypto_simd
cryptd
usbcore
glue_helper
lpc_ich
usb_common
wmi
button
video
i2c_hid
sdhci_acpi
dw_dmac
hid
dw_dmac_core
sdhci
battery
mmc_core

** PCI devices:
00:00.0 Host bridge [0600]: Intel Corporation Atom Processor Z36xxx/Z37xxx Series SoC Transaction Register [8086:0f00] (rev 09)
	Subsystem: ASUSTeK Computer Inc. Atom Processor Z36xxx/Z37xxx Series SoC Transaction Register [1043:14ed]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Kernel driver in use: iosf_mbi_pci

00:02.0 VGA compatible controller [0300]: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display [8086:0f31] (rev 09) (prog-if 00 [VGA controller])
	Subsystem: ASUSTeK Computer Inc. Atom Processor Z36xxx/Z37xxx Series Graphics & Display [1043:14ed]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 37
	Region 0: Memory at 90000000 (32-bit, non-prefetchable) [size=4M]
	Region 2: Memory at 80000000 (32-bit, prefetchable) [size=256M]
	Region 4: I/O ports at 1000 [size=8]
	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: i915
	Kernel modules: i915

00:14.0 USB controller [0c03]: Intel Corporation Atom Processor Z36xxx/Z37xxx, Celeron N2000 Series USB xHCI [8086:0f35] (rev 09) (prog-if 30 [XHCI])
	Subsystem: ASUSTeK Computer Inc. Atom Processor Z36xxx/Z37xxx, Celeron N2000 Series USB xHCI [1043:14ed]
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 35
	Region 0: Memory at 90800000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: <access denied>
	Kernel driver in use: xhci_hcd
	Kernel modules: xhci_pci

00:1a.0 Encryption controller [1080]: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Trusted Execution Engine [8086:0f18] (rev 09)
	Subsystem: ASUSTeK Computer Inc. Atom Processor Z36xxx/Z37xxx Series Trusted Execution Engine [1043:14ed]
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 255
	Region 0: Memory at 90700000 (32-bit, non-prefetchable) [size=1M]
	Region 1: Memory at 90600000 (32-bit, non-prefetchable) [size=1M]
	Capabilities: <access denied>

00:1f.0 ISA bridge [0601]: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Power Control Unit [8086:0f1c] (rev 09)
	Subsystem: ASUSTeK Computer Inc. Atom Processor Z36xxx/Z37xxx Series Power Control Unit [1043:14ed]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Capabilities: <access denied>
	Kernel driver in use: lpc_ich
	Kernel modules: lpc_ich


** USB devices:
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 0b05:17e0 ASUSTek Computer, Inc.
Bus 001 Device 002: ID 0b05:17e4 ASUSTek Computer, Inc.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


-- System Information:
Debian Release: 10.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.8.0-0.bpo.2-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_WARN
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE= (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages linux-image-5.8.0-0.bpo.2-amd64 depends on:
ii  initramfs-tools [linux-initramfs-tool]  0.133+deb10u1
ii  kmod                                    26-1
ii  linux-base                              4.6

Versions of packages linux-image-5.8.0-0.bpo.2-amd64 recommends:
ii  apparmor             2.13.2-10
ii  firmware-linux-free  3.4

Versions of packages linux-image-5.8.0-0.bpo.2-amd64 suggests:
pn  debian-kernel-handbook               <none>
pn  grub-pc | grub-efi-amd64 | extlinux  <none>
pn  linux-doc-5.8                        <none>

Versions of packages linux-image-5.8.0-0.bpo.2-amd64 is related to:
pn  firmware-amd-graphics     <none>
pn  firmware-atheros          <none>
pn  firmware-bnx2             <none>
pn  firmware-bnx2x            <none>
ii  firmware-brcm80211        20190114-2
pn  firmware-cavium           <none>
ii  firmware-intel-sound      20190114-2
pn  firmware-intelwimax       <none>
pn  firmware-ipw2x00          <none>
pn  firmware-ivtv             <none>
pn  firmware-iwlwifi          <none>
pn  firmware-libertas         <none>
pn  firmware-linux-nonfree    <none>
pn  firmware-misc-nonfree     <none>
pn  firmware-myricom          <none>
pn  firmware-netxen           <none>
pn  firmware-qlogic           <none>
pn  firmware-realtek          <none>
pn  firmware-samsung          <none>
pn  firmware-siano            <none>
pn  firmware-ti-connectivity  <none>
pn  xen-hypervisor            <none>

-- no debconf information

[toc] | [next] | [standalone]

#68516

Dear Maintainer,

I investigated a bit more this issue and upon further reading these 
sources regarding similar hardware:
- Backlight init fails on Surface 3 if module load order is wrong [1]
- Linux on the Dell Venue 8 Pro [2]

I gave a try at recompiling the linux kernel 5.8 from buster backports 
with these two main changes (full diff below):

> $ diff /boot/config-5.8.0-0.bpo.2-amd64 config-t100ta
> # [...]
> < CONFIG_I2C_DESIGNWARE_PCI=m
> ---
> > CONFIG_I2C_DESIGNWARE_PCI=y
> 8327c8327
> < # CONFIG_PWM_CRC is not set
> ---
> > CONFIG_PWM_CRC=y
> # [...]

The resulting kernel allows indeed to adjust the screen backlight and to 
completely turn it off, even though the following error message still 
appears:

> asus kernel: i915 0000:00:02.0: [drm] *ERROR* Failed to own gpio for 
>  panel control

Now the T100TA manages to go to suspend with the screen being completely 
turned off, when otherwise it usually stays turned on and just blank. I 
am not sure if the device can actually suspend to ram, even with this 
change only the suspend-to-idle seems available:

> $ cat /sys/power/mem_sleep 
> [s2idle]

Nevertheless, battery life is improved with this change.

Do you think this configuration can be applied as default? Baytrail 
chipset based devices would benefit of it.

Cheers

[1] https://gitlab.freedesktop.org/drm/intel/-/issues/26
[2] https://www.studioteabag.com/science/dell-venue-pro-linux/


Full kernel configuration diff:
> diff /boot/config-5.8.0-0.bpo.2-amd64 config-t100ta
> 5c5
> < CONFIG_CC_VERSION_TEXT="gcc-8 (Debian 8.3.0-6) 8.3.0"
> ---
> > CONFIG_CC_VERSION_TEXT="gcc (Debian 8.3.0-6) 8.3.0"
> 4134c4134
> < CONFIG_I2C_DESIGNWARE_PCI=m
> ---
> > CONFIG_I2C_DESIGNWARE_PCI=y
> 8327c8327
> < # CONFIG_PWM_CRC is not set
> ---
> > CONFIG_PWM_CRC=y
> 9138c9138
> < CONFIG_SYSTEM_TRUSTED_KEYS="debian/certs/debian-uefi-certs.pem"
> ---
> > CONFIG_SYSTEM_TRUSTED_KEYS=""
> 9296,9302c9296
> < CONFIG_DEBUG_INFO=y
> < # CONFIG_DEBUG_INFO_REDUCED is not set
> < # CONFIG_DEBUG_INFO_COMPRESSED is not set
> < # CONFIG_DEBUG_INFO_SPLIT is not set
> < # CONFIG_DEBUG_INFO_DWARF4 is not set
> < # CONFIG_DEBUG_INFO_BTF is not set
> < # CONFIG_GDB_SCRIPTS is not set
> ---
> > # CONFIG_DEBUG_INFO is not set

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#68707

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On Sat, 10 Oct 2020 16:25:56 +0200 /dev/fra <devfra@inventati.org> wrote:

> On the ASUS T100TA convertible laptop [1], and probably on similar
> devices with the same Intel Bay Trail chipset as well, the screen
> backlight cannot be adjusted and it is set to the maximum brightness.

I'm experiencing this same issue on Acer Aspire Switch 10 convertible
laptop which has Intel Atom Z3735F processor. At boot it shows "i915
0000:00:02.0: [drm] *ERROR* Failed to get the SoC PWM chip" error message.

Here's the relevant log from journalctl -xb:
```

Nov 28 11:23:16 debian kernel: fb0: switching to inteldrmfb from EFI VGA
Nov 28 11:23:16 debian kernel: Console: switching to colour dummy device 80x25
Nov 28 11:23:16 debian kernel: i915 0000:00:02.0: vgaarb: deactivate vga console
Nov 28 11:23:16 debian kernel: [drm] Supports vblank timestamp caching
Rev 2 (21.10.2013).
Nov 28 11:23:16 debian kernel: i915 0000:00:02.0: vgaarb: changed VGA
decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
Nov 28 11:23:16 debian kernel:  mmcblk1: p1 p2 p3
Nov 28 11:23:16 debian kernel: i915 0000:00:02.0: [drm] *ERROR* Failed
to get the SoC PWM chip
Nov 28 11:23:16 debian kernel: [drm] Initialized i915 1.6.0 20200515
for 0000:00:02.0 on minor 0
Nov 28 11:23:16 debian kernel: ACPI: Video Device [GFX0] (multi-head:
yes  rom: no  post: no)
Nov 28 11:23:16 debian kernel: acpi device:21: registered as cooling_device4
Nov 28 11:23:16 debian kernel: input: Video Bus as
/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input2
Nov 28 11:23:16 debian kernel: i915 0000:00:02.0: [drm] HDaudio
controller not detected, using LPE audio instead
Nov 28 11:23:16 debian kernel: fbcon: i915drmfb (fb0) is primary device
Nov 28 11:23:16 debian kernel: Console: switching to colour frame
buffer device 160x50
Nov 28 11:23:16 debian kernel: i915 0000:00:02.0: fb0: i915drmfb frame
buffer device

```

Here is the dmesg: https://pastebin.com/raw/2uGUYVkE

```

$ uname -a
Linux debian 5.8.0-0.bpo.2-amd64 #1 SMP Debian 5.8.10-1~bpo10+1
(2020-09-26) x86_64 GNU/Linux

$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 06cb:2968 Synaptics, Inc.
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ lspci
00:00.0 Host bridge: Intel Corporation Atom Processor Z36xxx/Z37xxx
Series SoC Transaction Register (rev 0f)
00:02.0 VGA compatible controller: Intel Corporation Atom Processor
Z36xxx/Z37xxx Series Graphics & Display (rev 0f)
00:14.0 USB controller: Intel Corporation Atom Processor
Z36xxx/Z37xxx, Celeron N2000 Series USB xHCI (rev 0f)
00:1a.0 Encryption controller: Intel Corporation Atom Processor
Z36xxx/Z37xxx Series Trusted Execution Engine (rev 0f)
00:1f.0 ISA bridge: Intel Corporation Atom Processor Z36xxx/Z37xxx
Series Power Control Unit (rev 0f)
$
```

For time being, I'm using xrandr to change perceived brightness as
suggested at https://wiki.archlinux.org/index.php/backlight#Xorg:_adjust_perceived_brightness_with_xrandr

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#69150

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Hi Everyone

I've recompiled the Debian Backports kernel 5.9.6 (with config changes
documented above by devfra@inventati.org) on the Asus T100TA along with an
i915 driver (in the firmware-misc-nonfree package) from Debian
buster-backports. I can confirm screen backlight can be adjusted and power
consumption is reduced. I also ran dmesg after triggering hibernation
(closing the laptop). It suggests the laptop is now moving into idle
without a problem, but can't enter into hibernation. It still seems to be
unable to find crystalcove, but now can control backlight with PWM.

Hope this helps!

Will

$sudo dmesg
...
[    0.000000] DMI: ASUSTeK COMPUTER INC. T100TAM/T100TAM, BIOS T100TAM.205
07/25/2014
...
[    3.972360] i915 0000:00:02.0: vgaarb: deactivate vga console
[    3.973773] i915 0000:00:02.0: vgaarb: changed VGA decodes:
olddecodes=io+mem,decodes=io+mem:owns=io+mem
[    3.974167] i915 0000:00:02.0: cannot find GPIO chip gpio_crystalcove,
deferring
[    3.974169] i915 0000:00:02.0: [drm] *ERROR* Failed to own gpio for
panel control
[    3.974697] i915 0000:00:02.0: [drm] Using PMIC PWM for LCD backlight
control
[    3.981676] [drm] Initialized i915 1.6.0 20200715 for 0000:00:02.0 on
minor 0
...
[ 3196.039364] PM: suspend entry (s2idle)
[ 3196.058281] Filesystems sync: 0.018 seconds
[ 3196.061135] (NULL device *): firmware: direct-loading firmware
regulatory.db
[ 3196.068645] (NULL device *): firmware: direct-loading firmware
brcm/brcmfmac43241b4-sdio.txt
[ 3196.068741] (NULL device *): firmware: direct-loading firmware
brcm/brcmfmac43241b4-sdio.bin
[ 3196.070542] (NULL device *): firmware: direct-loading firmware
intel/fw_sst_0f28.bin
[ 3196.071389] (NULL device *): firmware: direct-loading firmware
regulatory.db.p7s
[ 3196.071466] Freezing user space processes ... (elapsed 0.031 seconds)
done.
[ 3196.103199] OOM killer disabled.
[ 3196.103201] Freezing remaining freezable tasks ... (elapsed 0.001
seconds) done.
[ 3196.105184] printk: Suspending console(s) (use no_console_suspend to
debug)
[ 3196.154980] i2c_hid i2c-SIS0817:00: failed to change power setting.
[ 3200.390971] OOM killer enabled.
[ 3200.390973] Restarting tasks ... done.
[ 3200.421981] PM: suspend exit
[ 3217.236676] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

$ apt show firmware-misc-nonfree
Package: firmware-misc-nonfree
Version: 20200918-1~bpo10+1
...

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