iio: frequency: New driver for Analog Devices ADF4350/ADF4351 Wideban…

…d Synthesizers

Changes since V1:
Apply Jonathan's review feedback:
    Introduce and use IIO_ALTVOLTAGE.
    Fix up comments and documentation.
    Remove dead code.
    Reorder some code fragments.
    Add missing iio_device_free.

Convert to new API.
Fix-up out of staging includes.
Removed pll_locked attribute.

Changes since V2:
Use module_spi_driver.
adf4350_remove: move gpio_free after regulator.
target patch to drivers/iio

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-iio-frequency-adf4350

@@ -0,0 +1,21 @@
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_frequency_resolution
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Stores channel 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.
+
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_refin_frequency
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Sets channel 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_frequency
+		is updated. Consider to use out_altvoltageY_powerdown to power
+		down the PLL and it's RFOut buffers during REFin changes.

drivers/iio/frequency/Kconfig

@@ -19,5 +19,23 @@ config AD9523
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad9523.
 
+endmenu
+
+#
+# Phase-Locked Loop (PLL) frequency synthesizers
+#
+
+menu "Phase-Locked Loop (PLL) frequency synthesizers"
+
+config ADF4350
+	tristate "Analog Devices ADF4350/ADF4351 Wideband Synthesizers"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices  ADF4350/ADF4351
+	  Wideband Synthesizers. The driver provides direct access via sysfs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called adf4350.
+
 endmenu
 endmenu

drivers/iio/frequency/Makefile

@@ -3,3 +3,4 @@
 #
 
 obj-$(CONFIG_AD9523) += ad9523.o
+obj-$(CONFIG_ADF4350) += adf4350.o