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This version (05 Sep 2012 14:17) was approved by mhennerich.The Previously approved version (09 Nov 2011 10:33) is available.Diff

AD5398 Regulator Current Sink DAC Linux Driver

Supported Devices

Evaluation Boards

Description

AD5398 and AD5821 is a single 10-bit DAC with 120mA output current sink capability. I2C bus is connected to enable/disable output and set the proper output current value. This driver adapts to voltage and current regulator framework in Linux kernel.

Source Code

Status

Source Mainlined?
git Yes

Files

Function File
driver drivers/regulator/ad5398.c

Adding Linux driver support

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

The AD5398/AD5821 Driver depends on CONFIG_I2C

Select voltage and current regulator framework support and enable AD5398/AD5821 driver. Don't forget to select virtual regulator consumer and userspace regulator consumer as module. Because AD5398 driver is loaded after I2C bus finish initialization at kernel booting, built-in consumers may be loaded earlier and find supply in AD5398 driver is not available.

Linux Kernel Configuration
	Device Drivers  --->
		[*] Voltage and Current Regulator Support  --->
		<M>   Virtual regulator consumer support
		<M>   Userspace regulator consumer support
		<*>   Analog Devices AD5398/AD5821 regulators

Customize Device Parameters

The platform info defined in bf537-stamp board file is for ad5398 and ad5821 only. If you want to customize this driver for other compatible current regulator DAC, you should revise the platform information accordingly.

  • Define device supply name exported by the driver.

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct regulator_consumer_supply ad5398_consumer = {
	.supply = "current",
};
  • Define supply value range.

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct regulator_init_data ad5398_regulator_data = {
	.constraints = {
		.name = "current range",
		.max_uA = 120000,
		.valid_ops_mask = REGULATOR_CHANGE_CURRENT | REGULATOR_CHANGE_STATUS,
	},
	.num_consumer_supplies = 1,
	.consumer_supplies     = &ad5398_consumer,
};
  • Define supply name in platform_data for the virtual consumer to match and use.

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct platform_device ad5398_virt_consumer_device = {
	.name = "reg-virt-consumer",
	.id = 0,
	.dev = {
		.platform_data = "current", /* Passed to driver */
	},
};
  • Define supply name for the user space consumer to match and use.

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct regulator_bulk_data ad5398_bulk_data = {
	.supply = "current",
};

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct regulator_userspace_consumer_data ad5398_userspace_comsumer_data = {
	.name = "ad5398",
	.num_supplies = 1,
	.supplies = &ad5398_bulk_data,
};

file: arch/blackfin/mach-bf537/boards/stamp.c

static struct platform_device ad5398_userspace_consumer_device = {
	.name = "reg-userspace-consumer",
	.id = 0,
	.dev = {
		.platform_data = &ad5398_userspace_comsumer_data,
	},
};

Driver Testing

Check regulator driver initialization information at kernel booting.

This specifies any shell prompt running on the target

regulator: core version 0.5
i2c /dev entries driver
regulator: isink: 0 <--> 120 mA
ad5398 0-000c: ad5398 regulator driver loaded
i2c-bfin-twi i2c-bfin-twi.0: Blackfin BF5xx on-chip I2C TWI Contoller, regs_base@ffc01400

Check if AD5398 is probed properly.

This specifies any shell prompt running on the target

root:/> ls -l sys/class/regulator/regulator.0/
lrwxrwxrwx    1 root     root            0 Jan  1 19:47 device -> ../../../0-000c
-r--r--r--    1 root     root         4096 Jan  1 19:47 max_microamps
-r--r--r--    1 root     root         4096 Jan  1 19:47 microamps
-r--r--r--    1 root     root         4096 Jan  1 19:47 min_microamps
-r--r--r--    1 root     root         4096 Jan  1 19:47 name
-r--r--r--    1 root     root         4096 Jan  1 19:47 num_users
drwxr-xr-x    2 root     root            0 Jan  1 19:47 power
-r--r--r--    1 root     root         4096 Jan  1 19:47 requested_microamps
-r--r--r--    1 root     root         4096 Jan  1 19:47 state
lrwxrwxrwx    1 root     root            0 Jan  1 19:47 subsystem -> ../../../../../../../class/regulator
-r--r--r--    1 root     root         4096 Jan  1 19:47 suspend_disk_state
-r--r--r--    1 root     root         4096 Jan  1 19:47 suspend_mem_state
-r--r--r--    1 root     root         4096 Jan  1 19:47 suspend_standby_state
-r--r--r--    1 root     root         4096 Jan  1 19:47 type
-rw-r--r--    1 root     root         4096 Jan  1 19:47 uevent
root:/> cat sys/class/regulator/regulator.0/max_microamps
120000
root:/> cat sys/class/regulator/regulator.0/min_microamps
0
root:/> cat sys/class/regulator/regulator.0/name
current range
root:/> cat sys/class/regulator/regulator.0/type
current
root:/> cat sys/class/regulator/regulator.0/state
disabled

Insert virtual consumer driver module and check usability.

This specifies any shell prompt running on the target

root:/> modprobe virtual
root:/> ls -l sys/devices/platform/reg-virt-consumer.0/
lrwxrwxrwx    1 root     root            0 Jan  1 21:23 driver -> ../../../bus/platform/drivers/reg-virt-consumer
-rw-rw-rw-    1 root     root         4096 Jan  1 21:23 max_microamps
-rw-rw-rw-    1 root     root         4096 Jan  1 21:23 max_microvolts
-r--r--r--    1 root     root         4096 Jan  1 21:23 microamps_requested_current
-rw-rw-rw-    1 root     root         4096 Jan  1 21:23 min_microamps
-rw-rw-rw-    1 root     root         4096 Jan  1 21:23 min_microvolts
-r--r--r--    1 root     root         4096 Jan  1 21:23 modalias
-rw-rw-rw-    1 root     root         4096 Jan  1 21:23 mode
drwxr-xr-x    2 root     root            0 Jan  1 21:23 power
lrwxrwxrwx    1 root     root            0 Jan  1 21:23 subsystem -> ../../../bus/platform
-rw-r--r--    1 root     root         4096 Jan  1 21:23 uevent
root:/> cat sys/devices/platform/reg-virt-consumer.0/max_microamps
120000
root:/> cat sys/devices/platform/reg-virt-consumer.0/min_microamps
0
root:/> echo 50000 > sys/devices/platform/reg-virt-consumer.0/min_microamps
root:/> cat sys/devices/platform/reg-virt-consumer.0/min_microamps
50000
root:/> cat sys/devices/platform/reg-virt-consumer.0/max_microamps
120000

Insert user space consumer driver module and check usability.

This specifies any shell prompt running on the target

root:/> modprobe userspace-consumer
root:/> ls -l sys/devices/platform/reg-userspace-consumer.0/
lrwxrwxrwx    1 root     root            0 Jan  1 21:26 driver -> ../../../bus/platform/drivers/reg-userspace-consumer
-r--r--r--    1 root     root         4096 Jan  1 21:26 microamps_requested_current
-r--r--r--    1 root     root         4096 Jan  1 21:26 modalias
-r--r--r--    1 root     root         4096 Jan  1 21:26 name
drwxr-xr-x    2 root     root            0 Jan  1 21:26 power
-rw-r--r--    1 root     root         4096 Jan  1 21:26 state
lrwxrwxrwx    1 root     root            0 Jan  1 21:26 subsystem -> ../../../bus/platform
-rw-r--r--    1 root     root         4096 Jan  1 21:26 uevent
root:/> cat sys/devices/platform/reg-userspace-consumer.0/name
ad5398
root:/> cat sys/devices/platform/reg-userspace-consumer.0/state
disabled
root:/> echo enabled > sys/devices/platform/reg-userspace-consumer.0/state
root:/> cat sys/devices/platform/reg-userspace-consumer.0/state
enabled

To control ADC to output a given current, you only need to set the value to sysfs entry min_microamps in virtual consumer platform device. The driver adjusts the output according to the min current value received.