This version (09 Oct 2015 16:26) was approved by Lars-Peter Clausen.The Previously approved version (05 Sep 2012 14:16) is available.Diff

ADP5520/01 MFD Linux Driver

Supported Devices

Evaluation Boards


The ADP5520/01 driver utilizes several Linux device-driver subsystems and provides various software interfaces. It is therefore implemented as a multifunction device (MFD). In this particular case the ADP5520 backlight driver and I/O expander, concurrently leverages the Linux backlight, LED, GPIO, and input subsystems for its keypad functionality.


The ADP5520/01 core driver in drivers/mfd provides common services for the subsystem drivers. These services include register access, control and shared interrupt management.

The core registers/enumerates platform devices for the various subsystems via the platform device and driver system.

When a platform driver for one of the subsystems is instantiated, the core initializes the chip (which may be specified by the platform data).

The ADP5520/01 platform drivers follow the standard driver model convention, where discovery/enumeration is handled outside the drivers, and drivers provide probe() and remove() methods.


Each peripheral (subsystem device) has a view of the device which is implicitly narrowed to the specific set of resources that peripheral requires in order to function correctly.


The device driver uses a set of platform data to pass configurations through to the core and the subsidiary drivers so that there can be support for multiple ADP5520/01 devices built into a single kernel image.

Software configurable features


  • Ambient Light Sensor Support
  • Configurable Fade On/Off times
  • Configurable Brightness/Intensity in 127 steps


  • Up to 3 LEDs configurable
  • Configurable Fade On/Off times
  • LED Blink On/Off times
  • Configurable Brightness/Intensity in 64 steps from [0..255]


  • Configurable keypad size matrix (rows, columns) up to 16 keys
  • Enabling and disabling automatic key repeat feature.


  • Configurable number of dedicated GPIOs, up to 8 GPIOs
  • Configurable Pull-Ups

Source Code


Source Mainlined?
git Yes


Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

21 Oct 2010 16:10

Since Keypad, GPIO and optional LEDs (2, 3) are multiplexed, you need to avoid double configurations. Please refer to the table below.

ADP5520 PIN R3 R2 R1 R0 C0 C1 C2 C3

Please refer to include/linux/mfd/adp5520.h for detailed configuration defines.


<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_backlight_data{} c linux-kernel>


<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_leds[] c linux-kernel>

<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_leds_data{} c linux-kernel>


<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_gpio_data{} c linux-kernel>


<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_keymap[] c linux-kernel> <source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_keys_data{} c linux-kernel>

ADP5520/ADP5501 MFD Core Support

Declaring I2C devices

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: Documentation/i2c/instantiating-devices.rst

21 Oct 2010 16:10

<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:adp5520_pdev_data{} c linux-kernel> <source trunk/arch/blackfin/mach-bf537/boards/stamp.c:/CONFIG_PMIC_ADP5520/2-/#if/ c linux-kernel>

ADP5520 IRQ Usage:
If you aren’t planning to utilize the Keypad interface, you don’t need to specify an IRQ in bfin_i2c_board_info.

Adding Linux driver support

Fist of all you need to enable i2c support followed by the ADP5520 MFD Core Driver. Then you may select individual components like LCD backlight, LEDs, GPIOs and Keypad under the corresponding menus.

ADP5520 MFD Core Support

Device Drivers  ---> 
	<*> I2C support  --->
		<*> Blackfin TWI I2C support
		<*> GPIO-based bitbanging I2C

Device Drivers  ---> 
	Multifunction device drivers  --->
		[*] Analog Devices ADP5520/01 MFD PMIC Core Support


Device Drivers  ---> 
	Graphics support  --->
		[*] Backlight & LCD device support  --->
			<*>   Lowlevel Backlight controls
			<M>     Backlight Driver for ADP5520/ADP5501 using WLED


Device Drivers  --->
	[*] LED Support  --->
		<*>   LED Class Support
		<M>   LED Support for ADP5520/ADP5501 PMIC


Device Drivers  --->
	[*] GPIO Support  --->
		[*]   /sys/class/gpio/... (sysfs interface)
		<M>   GPIO Support for ADP5520 PMIC


Device Drivers  --->
	Input device support  --->
		<*> Generic input layer (needed for keyboard, mouse, ...)
		<*>   Event interface
		[*]   Keyboards  --->
			<M>   Keypad Support for ADP5520 PMIC

Hardware configuration

ADP5520 Demo Mother/Daughter Board

There is no dedicated Blackfin STAMP evaluation board for the ADP5520. During test and driver development we used the ADP5520 Demo Mother/Daughter Board. Connect the ADP5520 Demo Mother to an USB port.

It can be easily wired to the Blackfin STAMP TWI/I2C header.

BF537-STAMP (P10) TWI/I2C header ADP5520 Daughter Board
PIN Function PIN/Function

Driver testing


root:/> modprobe adp5520_bl

root:/> cd sys/class/backlight/adp5520-backlight/
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/backlight/adp5520-backlight> ls -l
-r--r--r--    1 root     root         4096 Nov 12 10:31 actual_brightness
-rw-r--r--    1 root     root         4096 Nov 12 10:31 bl_power
-rw-r--r--    1 root     root         4096 Nov 12 10:31 brightness
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 dark_dim
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 dark_max
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 daylight_dim
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 daylight_max
lrwxrwxrwx    1 root     root            0 Nov 12 10:31 device -> ../../../0-0032
-r--r--r--    1 root     root         4096 Nov 12 10:31 max_brightness
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 office_dim
-rw-rw-r--    1 root     root         4096 Nov 12 10:31 office_max
drwxr-xr-x    2 root     root            0 Nov 12 10:31 power
lrwxrwxrwx    1 root     root            0 Nov 12 10:31 subsystem -> ../../../../../../../../class/backlight

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/backlight/adp5520-backlight> echo 127 > brightness
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/backlight/adp5520-backlight> echo 50 > brightness
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/backlight/adp5520-backlight> echo 0 > brightness

For more information on Backlight handling in Linux read: Documentation/ABI/stable/sysfs-class-backlight


root:/> modprobe leds-adp5520
Registered led device: adp5520-led1
Registered led device: adp5520-led2
Registered led device: adp5520-led3

root:/> cd sys/class/leds/adp5520-led
sys/class/leds/adp5520-led1/  sys/class/leds/adp5520-led3/

root:/> cd sys/class/leds/adp5520-led1
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/leds/adp5520-led1> ls -l
-rw-r--r--    1 root     root         4096 Nov 12 10:34 brightness
lrwxrwxrwx    1 root     root            0 Nov 12 10:34 device -> ../../../0-0032
drwxr-xr-x    2 root     root            0 Nov 12 10:34 power
lrwxrwxrwx    1 root     root            0 Nov 12 10:34 subsystem -> ../../../../../../../../class/leds
-rw-r--r--    1 root     root         4096 Nov 12 10:34 trigger
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/leds/adp5520-led1> echo 10 > brightness
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/leds/adp5520-led1> echo 255 > brightness
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/leds/adp5520-led1> echo 0 > brightness

root:/> modprobe -r leds-adp5520

For more information on LEDs handling in Linux read: Documentation/leds-class.txt


root:/> modprobe adp5520-gpio
root:/> cd sys/class/gpio/gpiochip50/
root:/sys/devices/virtual/gpio/gpiochip50> ls -l
-r--r--r--    1 root     root         4096 Nov 12 10:37 base
-r--r--r--    1 root     root         4096 Nov 12 10:37 label
-r--r--r--    1 root     root         4096 Nov 12 10:37 ngpio
drwxr-xr-x    2 root     root            0 Nov 12 10:37 power
lrwxrwxrwx    1 root     root            0 Nov 12 10:37 subsystem -> ../../../../class/gpio
-rw-r--r--    1 root     root         4096 Nov 12 10:37 uevent
root:/sys/devices/virtual/gpio/gpiochip50> cd
Note that you will have to enable the event_test utility under “Blackfin test programs” in your user space configuration.
--- Blackfin test programs
                   [*] Input event device test

For more information on GPIO handling in Linux read: Documentation/gpio.txt


root:/> modprobe adp5520-keys
input: adp5520-keys as /devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-0032/adp5520-keys.5520/input/input0

root:/> event_test /dev/input/event0
Input driver version is 1.0.0
Input device ID: bus 0x18 vendor 0x1 product 0x5520 version 0x1
Input device name: "adp5520-keys"
Supported events:
  Event type 0 (Reset)
    Event code 0 (Reset)
    Event code 1 (Key)
  Event type 1 (Key)
    Event code 2 (1)
    Event code 3 (2)
    Event code 4 (3)
    Event code 5 (4)
    Event code 6 (5)
    Event code 7 (6)
    Event code 8 (7)
    Event code 9 (8)
    Event code 10 (9)
    Event code 11 (0)
    Event code 12 (Minus)
    Event code 13 (Equal)
    Event code 28 (Enter)
    Event code 41 (Grave)
    Event code 43 (BackSlash)
Testing ... (interrupt to exit)
Event: time 1415788674.340000, type 1 (Key), code 41 (Grave), value 1
Event: time 1415788674.340000, type 0 (Reset), code 0 (Reset), value 0
Event: time 1415788674.516000, type 1 (Key), code 41 (Grave), value 0
Event: time 1415788674.516000, type 0 (Reset), code 0 (Reset), value 0
Event: time 1415788674.912000, type 1 (Key), code 2 (1), value 1
Event: time 1415788674.912000, type 0 (Reset), code 0 (Reset), value 0
Event: time 1415788675.140000, type 1 (Key), code 2 (1), value 0
Event: time 1415788675.140000, type 0 (Reset), code 0 (Reset), value 0
Event: time 1415788675.892000, type 1 (Key), code 6 (5), value 1
Event: time 1415788675.892000, type 0 (Reset), code 0 (Reset), value 0
Event: time 1415788676.092000, type 1 (Key), code 6 (5), value 0
Event: time 1415788676.092000, type 0 (Reset), code 0 (Reset), value 0

root:/> modprobe -r adp5520-keys

For more information on Input handling in Linux read: Documentation/input/input.txt

More Information

1) , 2)
ADP5520 only
resources/tools-software/linux-drivers/multifunction-device/adp5520.txt · Last modified: 16 Feb 2015 11:50 by Lars-Peter Clausen