[solved] Intel Backlight not working

schard · 2017-12-05 15:19:12

Hi all,

Changing the backlight setting via /sys/class/backlight/intel_backlight/brightness does not work on a series of our digital signage systems:

Graphics card:

$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display (rev 0e)

On another series of similar devices with a radeon card, I can successfully set the display brightness via /sys/class/backlight/acpi_video0/brightness.
However the acpi_video0 is not available on the Intel devices.

I tried the following boot parameters with both, linux.4.13.12-1 and linux-lts-4.9.65-1:

acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=none
video.use_native_backlight=0
video.use_native_backlight=1
acpi_osi=Linux
acpi_osi=

I also tried the config file /etc/X11/xorg.conf.d/20-intel.conf containing:

Section "Device"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        Identifier "card0"
EndSection

Same result on all options:
I only have /sys/class/backlight/intel_backlight available, no acpi_video0.
Setting and getting backlight values from brightness resp. actual_brightness there works as desired.
Actual screen brightness, however, does not change.

What am I doing wrong?

Update
I now also tried the following boot parameters without any noticable change in behaviour:

acpi_osi=Linux
acpi_osi="!Windows 2012"
acpi_osi=

Here's some more hardware info:

# dmidecode 3.1
Getting SMBIOS data from sysfs.
SMBIOS 2.8 present.
51 structures occupying 1756 bytes.
Table at 0x000EBF30.

Handle 0x0000, DMI type 0, 24 bytes
BIOS Information
	Vendor: American Megatrends Inc.
	Version: 5.6.5
	Release Date: 01/22/2015
	Address: 0xF0000
	Runtime Size: 64 kB
	ROM Size: 1024 kB
	Characteristics:
		PCI is supported
		BIOS is upgradeable
		BIOS shadowing is allowed
		Boot from CD is supported
		Selectable boot is supported
		BIOS ROM is socketed
		EDD is supported
		5.25"/1.2 MB floppy services are supported (int 13h)
		Print screen service is supported (int 5h)
		8042 keyboard services are supported (int 9h)
		Serial services are supported (int 14h)
		Printer services are supported (int 17h)
		ACPI is supported
		USB legacy is supported
		BIOS boot specification is supported
		Targeted content distribution is supported
		UEFI is supported
	BIOS Revision: 5.6

Handle 0x0001, DMI type 1, 27 bytes
System Information
	Manufacturer:  
	Product Name:  
	Version:  
	Serial Number:  
	UUID: 03000200-0400-0500-0006-000700080009
	Wake-up Type: Power Switch
	SKU Number:  
	Family:  

Handle 0x0002, DMI type 2, 15 bytes
Base Board Information
	Manufacturer:  
	Product Name:  
	Version:  
	Serial Number:  
	Asset Tag:  
	Features:
		Board is a hosting board
		Board is replaceable
	Location In Chassis:  
	Chassis Handle: 0x0003
	Type: Motherboard
	Contained Object Handles: 0

Handle 0x0003, DMI type 3, 25 bytes
Chassis Information
	Manufacturer:  
	Type: Desktop
	Lock: Not Present
	Version: To Be Filled By O.E.M.
	Serial Number: To Be Filled By O.E.M.
	Asset Tag: To Be Filled By O.E.M.
	Boot-up State: Safe
	Power Supply State: Safe
	Thermal State: Safe
	Security Status: None
	OEM Information: 0x00000000
	Height: Unspecified
	Number Of Power Cords: 1
	Contained Elements: 1
		<OUT OF SPEC> (0)
	SKU Number: To be filled by O.E.M.

Handle 0x0008, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J1A1
	Internal Connector Type: None
	External Reference Designator: PS2Mouse
	External Connector Type: PS/2
	Port Type: Mouse Port

Handle 0x0009, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J1A1
	Internal Connector Type: None
	External Reference Designator: Keyboard
	External Connector Type: PS/2
	Port Type: Keyboard Port

Handle 0x000A, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2A1
	Internal Connector Type: None
	External Reference Designator: TV Out
	External Connector Type: Mini Centronics Type-14
	Port Type: Other

Handle 0x000B, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2A2A
	Internal Connector Type: None
	External Reference Designator: COM A
	External Connector Type: DB-9 male
	Port Type: Serial Port 16550A Compatible

Handle 0x000C, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2A2B
	Internal Connector Type: None
	External Reference Designator: Video
	External Connector Type: DB-15 female
	Port Type: Video Port

Handle 0x000D, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J3A1
	Internal Connector Type: None
	External Reference Designator: USB1
	External Connector Type: Access Bus (USB)
	Port Type: USB

Handle 0x000E, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J3A1
	Internal Connector Type: None
	External Reference Designator: USB2
	External Connector Type: Access Bus (USB)
	Port Type: USB

Handle 0x000F, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J3A1
	Internal Connector Type: None
	External Reference Designator: USB3
	External Connector Type: Access Bus (USB)
	Port Type: USB

Handle 0x0010, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9A1 - TPM HDR
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0011, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9C1 - PCIE DOCKING CONN
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0012, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2B3 - CPU FAN
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0013, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J6C2 - EXT HDMI
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0014, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J3C1 - GMCH FAN
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0015, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J1D1 - ITP
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0016, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9E2 - MDC INTPSR
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0017, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9E4 - MDC INTPSR
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0018, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9E3 - LPC HOT DOCKING
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0019, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9E1 - SCAN MATRIX
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001A, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J9G1 - LPC SIDE BAND
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001B, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J8F1 - UNIFIED
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001C, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J6F1 - LVDS
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001D, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2F1 - LAI FAN
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001E, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J2G1 - GFX VID
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x001F, DMI type 8, 9 bytes
Port Connector Information
	Internal Reference Designator: J1G6 - AC JACK
	Internal Connector Type: Other
	External Reference Designator: Not Specified
	External Connector Type: None
	Port Type: Other

Handle 0x0020, DMI type 9, 17 bytes
System Slot Information
	Designation: J6B2
	Type: x16 PCI Express
	Current Usage: In Use
	Length: Long
	ID: 0
	Characteristics:
		3.3 V is provided
		Opening is shared
		PME signal is supported
	Bus Address: 0000:00:01.0

Handle 0x0021, DMI type 9, 17 bytes
System Slot Information
	Designation: J6B1
	Type: x1 PCI Express
	Current Usage: In Use
	Length: Short
	ID: 1
	Characteristics:
		3.3 V is provided
		Opening is shared
		PME signal is supported
	Bus Address: 0000:00:1c.3

Handle 0x0022, DMI type 9, 17 bytes
System Slot Information
	Designation: J6D1
	Type: x1 PCI Express
	Current Usage: In Use
	Length: Short
	ID: 2
	Characteristics:
		3.3 V is provided
		Opening is shared
		PME signal is supported
	Bus Address: 0000:00:1c.4

Handle 0x0023, DMI type 9, 17 bytes
System Slot Information
	Designation: J7B1
	Type: x1 PCI Express
	Current Usage: In Use
	Length: Short
	ID: 3
	Characteristics:
		3.3 V is provided
		Opening is shared
		PME signal is supported
	Bus Address: 0000:00:1c.5

Handle 0x0024, DMI type 9, 17 bytes
System Slot Information
	Designation: J8B4
	Type: x1 PCI Express
	Current Usage: In Use
	Length: Short
	ID: 4
	Characteristics:
		3.3 V is provided
		Opening is shared
		PME signal is supported
	Bus Address: 0000:00:1c.6

Handle 0x0025, DMI type 10, 6 bytes
On Board Device Information
	Type: Video
	Status: Enabled
	Description:     

Handle 0x0026, DMI type 11, 5 bytes
OEM Strings
	String 1: To Be Filled By O.E.M.

Handle 0x0027, DMI type 12, 5 bytes
System Configuration Options
	Option 1: To Be Filled By O.E.M.

Handle 0x0028, DMI type 16, 23 bytes
Physical Memory Array
	Location: System Board Or Motherboard
	Use: System Memory
	Error Correction Type: None
	Maximum Capacity: 8 GB
	Error Information Handle: Not Provided
	Number Of Devices: 2

Handle 0x0029, DMI type 19, 31 bytes
Memory Array Mapped Address
	Starting Address: 0x00000000000
	Ending Address: 0x000FFFFFFFF
	Range Size: 4 GB
	Physical Array Handle: 0x0028
	Partition Width: 2

Handle 0x002A, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0028
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 4096 MB
	Form Factor: DIMM
	Set: None
	Locator: A1_DIMM0
	Bank Locator: A1_BANK0
	Type: DDR3
	Type Detail: Unknown
	Speed: 1600 MT/s
	Manufacturer: Samsung         
	Serial Number: 16A95F5A  
	Asset Tag: A1_AssetTagNum0
	Part Number: M471B5173EB0-YK0  
	Rank: 1
	Configured Clock Speed: 1333 MT/s
	Minimum Voltage: 1.35 V
	Maximum Voltage: 1.5 V
	Configured Voltage: 1.35 V

Handle 0x002B, DMI type 20, 35 bytes
Memory Device Mapped Address
	Starting Address: 0x00000000000
	Ending Address: 0x000FFFFFFFF
	Range Size: 4 GB
	Physical Device Handle: 0x002A
	Memory Array Mapped Address Handle: 0x0029
	Partition Row Position: Unknown
	Interleave Position: 1
	Interleaved Data Depth: 2

Handle 0x002C, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0028
	Error Information Handle: Not Provided
	Total Width: Unknown
	Data Width: 64 bits
	Size: No Module Installed
	Form Factor: DIMM
	Set: None
	Locator: A1_DIMM1
	Bank Locator: A1_BANK1
	Type: Unknown
	Type Detail: Unknown
	Speed: Unknown
	Manufacturer: A1_Manufacturer1
	Serial Number: A1_SerNum1
	Asset Tag: A1_AssetTagNum1
	Part Number: Array1_PartNumber1
	Rank: Unknown
	Configured Clock Speed: Unknown
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: Unknown

Handle 0x002D, DMI type 126, 35 bytes
Inactive

Handle 0x002E, DMI type 32, 20 bytes
System Boot Information
	Status: No errors detected

Handle 0x002F, DMI type 41, 11 bytes
Onboard Device
	Reference Designation:  Onboard IGD
	Type: Video
	Status: Enabled
	Type Instance: 1
	Bus Address: 0000:00:02.0

Handle 0x0030, DMI type 41, 11 bytes
Onboard Device
	Reference Designation:  Onboard LAN
	Type: Ethernet
	Status: Enabled
	Type Instance: 1
	Bus Address: 0000:00:19.0

Handle 0x0031, DMI type 41, 11 bytes
Onboard Device
	Reference Designation:  Onboard 1394
	Type: Other
	Status: Enabled
	Type Instance: 1
	Bus Address: 0000:03:1c.2

Handle 0x0032, DMI type 7, 19 bytes
Cache Information
	Socket Designation: CPU Internal L1
	Configuration: Enabled, Not Socketed, Level 1
	Operational Mode: Write Back
	Location: Internal
	Installed Size: 224 kB
	Maximum Size: 224 kB
	Supported SRAM Types:
		Unknown
	Installed SRAM Type: Unknown
	Speed: Unknown
	Error Correction Type: Single-bit ECC
	System Type: Other
	Associativity: Other

Handle 0x0033, DMI type 7, 19 bytes
Cache Information
	Socket Designation: CPU Internal L2
	Configuration: Enabled, Not Socketed, Level 2
	Operational Mode: Write Back
	Location: Internal
	Installed Size: 2048 kB
	Maximum Size: 2048 kB
	Supported SRAM Types:
		Unknown
	Installed SRAM Type: Unknown
	Speed: Unknown
	Error Correction Type: Single-bit ECC
	System Type: Unified
	Associativity: 16-way Set-associative

Handle 0x0034, DMI type 4, 42 bytes
Processor Information
	Socket Designation: SOCKET 0
	Type: Central Processor
	Family: Celeron
	Manufacturer: Intel
	ID: 78 06 03 00 FF FB EB BF
	Signature: Type 0, Family 6, Model 55, Stepping 8
	Flags:
		FPU (Floating-point unit on-chip)
		VME (Virtual mode extension)
		DE (Debugging extension)
		PSE (Page size extension)
		TSC (Time stamp counter)
		MSR (Model specific registers)
		PAE (Physical address extension)
		MCE (Machine check exception)
		CX8 (CMPXCHG8 instruction supported)
		APIC (On-chip APIC hardware supported)
		SEP (Fast system call)
		MTRR (Memory type range registers)
		PGE (Page global enable)
		MCA (Machine check architecture)
		CMOV (Conditional move instruction supported)
		PAT (Page attribute table)
		PSE-36 (36-bit page size extension)
		CLFSH (CLFLUSH instruction supported)
		DS (Debug store)
		ACPI (ACPI supported)
		MMX (MMX technology supported)
		FXSR (FXSAVE and FXSTOR instructions supported)
		SSE (Streaming SIMD extensions)
		SSE2 (Streaming SIMD extensions 2)
		SS (Self-snoop)
		HTT (Multi-threading)
		TM (Thermal monitor supported)
		PBE (Pending break enabled)
	Version: Intel(R) Celeron(R) CPU N2930 @ 1.83GHz
	Voltage: 1.2 V
	External Clock: 83 MHz
	Max Speed: 2400 MHz
	Current Speed: 1830 MHz
	Status: Populated, Enabled
	Upgrade: Socket BGA1155
	L1 Cache Handle: 0x0032
	L2 Cache Handle: 0x0033
	L3 Cache Handle: Not Provided
	Serial Number: Not Specified
	Asset Tag: Fill By OEM
	Part Number: Fill By OEM
	Core Count: 4
	Core Enabled: 4
	Thread Count: 4
	Characteristics:
		64-bit capable

Handle 0x0035, DMI type 13, 22 bytes
BIOS Language Information
	Language Description Format: Long
	Installable Languages: 1
		en|US|iso8859-1
	Currently Installed Language: en|US|iso8859-1

Handle 0x0036, DMI type 127, 4 bytes
End Of Table

hwinfo --gfxcard
11: PCI 02.0: 0300 VGA compatible controller (VGA)              
  [Created at pci.378]
  Unique ID: _Znp.H65rpC2Tns8
  SysFS ID: /devices/pci0000:00/0000:00:02.0
  SysFS BusID: 0000:00:02.0
  Hardware Class: graphics card
  Device Name: "Onboard IGD"
  Model: "Intel Atom Processor Z36xxx/Z37xxx Series Graphics & Display"
  Vendor: pci 0x8086 "Intel Corporation"
  Device: pci 0x0f31 "Atom Processor Z36xxx/Z37xxx Series Graphics & Display"
  SubVendor: pci 0x8086 "Intel Corporation"
  SubDevice: pci 0x0f31 
  Revision: 0x0e
  Driver: "i915"
  Driver Modules: "i915"
  Memory Range: 0xd0000000-0xd03fffff (rw,non-prefetchable)
  Memory Range: 0xc0000000-0xcfffffff (ro,non-prefetchable)
  I/O Ports: 0xf080-0xf087 (rw)
  Memory Range: 0x000c0000-0x000dffff (rw,non-prefetchable,disabled)
  IRQ: 92 (85 events)
  Module Alias: "pci:v00008086d00000F31sv00008086sd00000F31bc03sc00i00"
  Driver Info #0:
    Driver Status: i915 is active
    Driver Activation Cmd: "modprobe i915"
  Config Status: cfg=new, avail=yes, need=no, active=unknown

Primary display adapter: #11

Solved:
The built-in card does not work with the native ACPI interface because of an intermediary LVDS converter.
After further communication with the manufacturer of the devices, we got a firmware update for it that allows to set the brightness via SMBUS/I2C.

Last edited by schard (2018-09-24 13:52:45)

Arch Linux

#1 2017-12-05 15:19:12

[solved] Intel Backlight not working

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