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This version (06 Feb 2014 11:34) was approved by larsc.The Previously approved version (18 Feb 2013 15:45) is available.Diff

ADF4350 IIO Wideband Synthesizer Linux Driver

Supported Devices

Reference Circuits

Evaluation Boards

Description

This is a Linux industrial I/O (IIO) subsystem driver, targeting serial interface PLL Synthesizers. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See IIO for more information.

Source Code

Status

Source Mainlined?
git Yes

Files

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 · Michael Hennerich

The reference frequency and GPIO numbers may vary between boards. The platform_data for the device's “struct device” holds this information.

/**
 * struct adf4350_platform_data - platform specific information
 * @clkin:		REFin frequency in Hz.
 * @channel_spacing:	Channel spacing in Hz (influences MODULUS).
 * @power_up_frequency:	Optional, If set in Hz the PLL tunes to the desired
 *			frequency on probe.
 * @ref_div_factor:	Optional, if set the driver skips dynamic calculation
 *			and uses this default value instead.
 * @ref_doubler_en:	Enables reference doubler.
 * @ref_div2_en:	Enables reference divider.
 * @r2_user_settings:	User defined settings for ADF4350/1 REGISTER_2.
 * @r3_user_settings:	User defined settings for ADF4350/1 REGISTER_3.
 * @r4_user_settings:	User defined settings for ADF4350/1 REGISTER_4.
 * @gpio_lock_detect:	Optional, if set with a valid GPIO number,
 *			a PLL_LOCKED device attribute is created.
 *			If not used - set to -1.
 */
 
struct adf4350_platform_data {
	unsigned long		clkin;
	unsigned long		channel_spacing;
	unsigned long long	power_up_frequency;
 
	unsigned short		ref_div_factor; /* 10-bit R counter */
	bool			ref_doubler_en;
	bool			ref_div2_en;
 
	unsigned		r2_user_settings;
	unsigned		r3_user_settings;
	unsigned		r4_user_settings;
	int			gpio_lock_detect;
};
static struct adf4350_platform_data adf4351_pdata = {
	.clkin = 10000000,
	.channel_spacing = 10000,
	.r2_user_settings = ADF4350_REG2_PD_POLARITY_POS,
			    ADF4350_REG2_CHARGE_PUMP_CURR_uA(2500),
	.r3_user_settings = ADF4350_REG3_12BIT_CLKDIV_MODE(0),
	.r4_user_settings = ADF4350_REG4_OUTPUT_PWR(0) |
			    ADF4350_REG4_MUTE_TILL_LOCK_EN,
	.gpio_lock_detect = -1,
};

Declaring SPI slave devices

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

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

For more information see: Documentation/spi/spi-summary

21 Oct 2010 16:10 · Michael Hennerich

Depending on the DDS IC used, you may need to set the modalias accordingly, matching your part name. It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.

static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_ADF4350) || defined(CONFIG_ADF4350_MODULE)
	{
		.modalias = "adf4350",
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = GPIO_PF10 + MAX_CTRL_CS,	/* GPIO controlled SSEL */
		.platform_data = NULL, /* No spi_driver specific config */
		.mode = SPI_MODE_0,
	},
#endif
};
static int __init board_init(void)
{
	[--snip--]
 
	spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));
 
	[--snip--]
 
	return 0;
}
arch_initcall(board_init);

Adding Linux driver support

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

The ADF4350 Driver depends on CONFIG_SPI

Linux Kernel Configuration
	Device Drivers  --->
		<*>     Industrial I/O support --->
		    --- Industrial I/O support
		    -*-   Enable ring buffer support within IIO
		    -*-     Industrial I/O lock free software ring
		    -*-   Enable triggered sampling support

			          *** Phase-Locked Loop (PLL) frequency synthesizers ***

		    [--snip--]
			    <*>   Analog Devices ADF4350/ADF4351 Wideband Synthesizers
		    [--snip--]

Hardware configuration

Driver testing

Each and every IIO device, typically a hardware chip, has a device folder under /sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under every of these directory folders reside a set of files, depending on the characteristics and features of the hardware device in question. These files are consistently generalized and documented in the IIO ABI documentation. In order to determine which IIO deviceX corresponds to which hardware device, the user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case the sequence in which the iio device drivers are loaded/registered is constant, the numbering is constant and may be known in advance.

02 Mar 2011 15:16 · Michael Hennerich

This specifies any shell prompt running on the target

root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
iio:device0
root:/sys/bus/iio/devices> iio:device0

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> ls -l
-r--r--r--    1 root     root          4096 Jan  1 00:01 dev
-r--r--r--    1 root     root          4096 Jan  1 00:01 name
-rw-r--r--    1 root     root          4096 Jan  1 00:01 out_altvoltage0_frequency
-rw-r--r--    1 root     root          4096 Jan  1 00:01 out_altvoltage0_frequency_resolution
-r--r--r--    1 root     root          4096 Jan  1 00:01 out_altvoltage0_locked
-rw-r--r--    1 root     root          4096 Jan  1 00:01 out_altvoltage0_powerdown
-rw-r--r--    1 root     root          4096 Jan  1 00:01 out_altvoltage0_refin_frequency
drwxr-xr-x    2 root     root             0 Jan  1 00:01 power
lrwxrwxrwx    1 root     root             0 Jan  1 00:01 subsystem -> ../../../../../bus/iio
-rw-r--r--    1 root     root          4096 Jan  1 00:01 uevent

Show device name

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat name
adf4350

Set Output Frequency

/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_frequency

Stores PLL Y frequency in Hz. Reading returns the actual frequency in Hz. When setting a new frequency, the PLL requires some time to lock. If available, the user can read out_altvoltageY_locked in order to check whether the PLL has locked or not.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 144825000 > out_altvoltage0_frequency
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltage0_frequency
144825000

Set frequency resolution/channel spacing

/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_freq_resolution

Stores PLL Y frequency resolution/channel spacing in Hz. The value given directly influences the MODULUS used by the fractional-N PLL. It is assumed that the algorithm that is used to compute the various dividers, is able to generate proper values for multiples of channel spacing.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 10000 > out_altvoltageY_refin_freq
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltageY_refin_frequency
10000

Set reference frequency

/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_refin_frequency

Sets PLL Y REFin frequency in Hz. In some clock chained applications, the reference frequency used by the PLL may change during runtime. This attribute allows the user to adjust the reference frequency accordingly. The value written has no effect until out_altvoltageY_freq is updated.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 10000000 > out_altvoltageY_refin_frequency
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltageY_refin_frequency
10000000

Enable Power-Down

/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_powerdown

If available, this attribute allows the user to power down the PLL and it's RFOut buffers. This is in particular useful during REFin changes.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 1 > out_altvoltageY_powerdown
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltageY_powerdown
1

Enable Power-Down

/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_locked

If available, this attribute allows the user to determine whether the PLL has locked by reading '1' or not '0'.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltageY_locked
1

More Information