iio: frequency: New driver for AD9523 SPI Low Jitter Clock Generator

Changes since V1:

Apply Jonathan's review feedback:
Revise device status attribute names, and split documentation into two sections.
Add additional comments, and fix indention issues.
Remove pointless zero initializations.
Revise return value handling.
Simplify some code sections.
Split store_eeprom and sync handling into separate functions.
Use strtobool where applicable.
Document platform data structures using kernel-doc style.

Use dev_to_iio_dev
write_raw IIO_CHAN_INFO_FREQUENCY: Reject values <= 0
Make patch target drivers/iio

Changes since V2:

Use for_each_clear_bit() and __set_bit() where applicable.
Add descriptive comment.
Avoid temporary for struct regulator.
spi_device_id name use ad9523-1, ad9523 will be added later.

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-ad9523

@@ -0,0 +1,37 @@
+What:		/sys/bus/iio/devices/iio:deviceX/pll2_feedback_clk_present
+What:		/sys/bus/iio/devices/iio:deviceX/pll2_reference_clk_present
+What:		/sys/bus/iio/devices/iio:deviceX/pll1_reference_clk_a_present
+What:		/sys/bus/iio/devices/iio:deviceX/pll1_reference_clk_b_present
+What:		/sys/bus/iio/devices/iio:deviceX/pll1_reference_clk_test_present
+What:		/sys/bus/iio/devices/iio:deviceX/vcxo_clk_present
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Reading returns either '1' or '0'.
+		'1' means that the clock in question is present.
+		'0' means that the clock is missing.
+
+What:		/sys/bus/iio/devices/iio:deviceX/pllY_locked
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Reading returns either '1' or '0'. '1' means that the
+		pllY is locked.
+
+What:		/sys/bus/iio/devices/iio:deviceX/store_eeprom
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Writing '1' stores the current device configuration into
+		on-chip EEPROM. After power-up or chip reset the device will
+		automatically load the saved configuration.
+
+What:		/sys/bus/iio/devices/iio:deviceX/sync_dividers
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Writing '1' triggers the clock distribution synchronization
+		functionality. All dividers are reset and the channels start
+		with their predefined phase offsets (out_altvoltageY_phase).
+		Writing this file has the effect as driving the external
+		/SYNC pin low.

drivers/iio/Kconfig

@@ -51,5 +51,6 @@ config IIO_CONSUMERS_PER_TRIGGER
 source "drivers/iio/adc/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"
 source "drivers/iio/light/Kconfig"
+source "drivers/iio/frequency/Kconfig"
 
 endif # IIO

drivers/iio/Makefile

@@ -12,3 +12,4 @@ obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
 obj-y += adc/
 obj-y += amplifiers/
 obj-y += light/
+obj-y += frequency/

drivers/iio/frequency/Kconfig

@@ -0,0 +1,23 @@
+#
+# Frequency
+#	Direct Digital Synthesis drivers (DDS)
+#	Clock Distribution device drivers
+#	Phase-Locked Loop (PLL) frequency synthesizers
+#
+
+menu "Frequency Synthesizers DDS/PLL"
+
+menu "Clock Generator/Distribution"
+
+config AD9523
+	tristate "Analog Devices AD9523 Low Jitter Clock Generator"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices AD9523 Low Jitter
+	  Clock Generator. The driver provides direct access via sysfs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad9523.
+
+endmenu
+endmenu

drivers/iio/frequency/Makefile

@@ -0,0 +1,5 @@
+#
+# Makefile iio/frequency
+#
+
+obj-$(CONFIG_AD9523) += ad9523.o

include/linux/iio/frequency/ad9523.h

@@ -0,0 +1,195 @@
+/*
+ * AD9523 SPI Low Jitter Clock Generator
+ *
+ * Copyright 2012 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#ifndef IIO_FREQUENCY_AD9523_H_
+#define IIO_FREQUENCY_AD9523_H_
+
+enum outp_drv_mode {
+	TRISTATE,
+	LVPECL_8mA,
+	LVDS_4mA,
+	LVDS_7mA,
+	HSTL0_16mA,
+	HSTL1_8mA,
+	CMOS_CONF1,
+	CMOS_CONF2,
+	CMOS_CONF3,
+	CMOS_CONF4,
+	CMOS_CONF5,
+	CMOS_CONF6,
+	CMOS_CONF7,
+	CMOS_CONF8,
+	CMOS_CONF9
+};
+
+enum ref_sel_mode {
+	NONEREVERTIVE_STAY_ON_REFB,
+	REVERT_TO_REFA,
+	SELECT_REFA,
+	SELECT_REFB,
+	EXT_REF_SEL
+};
+
+/**
+ * struct ad9523_channel_spec - Output channel configuration
+ *
+ * @channel_num: Output channel number.
+ * @divider_output_invert_en: Invert the polarity of the output clock.
+ * @sync_ignore_en: Ignore chip-level SYNC signal.
+ * @low_power_mode_en: Reduce power used in the differential output modes.
+ * @use_alt_clock_src: Channel divider uses alternative clk source.
+ * @output_dis: Disables, powers down the entire channel.
+ * @driver_mode: Output driver mode (logic level family).
+ * @divider_phase: Divider initial phase after a SYNC. Range 0..63
+		   LSB = 1/2 of a period of the divider input clock.
+ * @channel_divider: 10-bit channel divider.
+ * @extended_name: Optional descriptive channel name.
+ */
+
+struct ad9523_channel_spec {
+	unsigned		channel_num;
+	bool			divider_output_invert_en;
+	bool			sync_ignore_en;
+	bool			low_power_mode_en;
+				 /* CH0..CH3 VCXO, CH4..CH9 VCO2 */
+	bool			use_alt_clock_src;
+	bool			output_dis;
+	enum outp_drv_mode	driver_mode;
+	unsigned char		divider_phase;
+	unsigned short		channel_divider;
+	char			extended_name[16];
+};
+
+enum pll1_rzero_resistor {
+	RZERO_883_OHM,
+	RZERO_677_OHM,
+	RZERO_341_OHM,
+	RZERO_135_OHM,
+	RZERO_10_OHM,
+	RZERO_USE_EXT_RES = 8,
+};
+
+enum rpole2_resistor {
+	RPOLE2_900_OHM,
+	RPOLE2_450_OHM,
+	RPOLE2_300_OHM,
+	RPOLE2_225_OHM,
+};
+
+enum rzero_resistor {
+	RZERO_3250_OHM,
+	RZERO_2750_OHM,
+	RZERO_2250_OHM,
+	RZERO_2100_OHM,
+	RZERO_3000_OHM,
+	RZERO_2500_OHM,
+	RZERO_2000_OHM,
+	RZERO_1850_OHM,
+};
+
+enum cpole1_capacitor {
+	CPOLE1_0_PF,
+	CPOLE1_8_PF,
+	CPOLE1_16_PF,
+	CPOLE1_24_PF,
+	_CPOLE1_24_PF, /* place holder */
+	CPOLE1_32_PF,
+	CPOLE1_40_PF,
+	CPOLE1_48_PF,
+};
+
+/**
+ * struct ad9523_platform_data - platform specific information
+ *
+ * @vcxo_freq: External VCXO frequency in Hz
+ * @refa_diff_rcv_en: REFA differential/single-ended input selection.
+ * @refb_diff_rcv_en: REFB differential/single-ended input selection.
+ * @zd_in_diff_en: Zero Delay differential/single-ended input selection.
+ * @osc_in_diff_en: OSC differential/ single-ended input selection.
+ * @refa_cmos_neg_inp_en: REFA single-ended neg./pos. input enable.
+ * @refb_cmos_neg_inp_en: REFB single-ended neg./pos. input enable.
+ * @zd_in_cmos_neg_inp_en: Zero Delay single-ended neg./pos. input enable.
+ * @osc_in_cmos_neg_inp_en: OSC single-ended neg./pos. input enable.
+ * @refa_r_div: PLL1 10-bit REFA R divider.
+ * @refb_r_div: PLL1 10-bit REFB R divider.
+ * @pll1_feedback_div: PLL1 10-bit Feedback N divider.
+ * @pll1_charge_pump_current_nA: Magnitude of PLL1 charge pump current (nA).
+ * @zero_delay_mode_internal_en: Internal, external Zero Delay mode selection.
+ * @osc_in_feedback_en: PLL1 feedback path, local feedback from
+ *			the OSC_IN receiver or zero delay mode
+ * @pll1_loop_filter_rzero: PLL1 Loop Filter Zero Resistor selection.
+ * @ref_mode: Reference selection mode.
+ * @pll2_charge_pump_current_nA: Magnitude of PLL2 charge pump current (nA).
+ * @pll2_ndiv_a_cnt: PLL2 Feedback N-divider, A Counter, range 0..4.
+ * @pll2_ndiv_b_cnt: PLL2 Feedback N-divider, B Counter, range 0..63.
+ * @pll2_freq_doubler_en: PLL2 frequency doubler enable.
+ * @pll2_r2_div: PLL2 R2 divider, range 0..31.
+ * @pll2_vco_diff_m1: VCO1 divider, range 3..5.
+ * @pll2_vco_diff_m2: VCO2 divider, range 3..5.
+ * @rpole2: PLL2 loop filter Rpole resistor value.
+ * @rzero: PLL2 loop filter Rzero resistor value.
+ * @cpole1: PLL2 loop filter Cpole capacitor value.
+ * @rzero_bypass_en: PLL2 loop filter Rzero bypass enable.
+ * @num_channels: Array size of struct ad9523_channel_spec.
+ * @channels: Pointer to channel array.
+ * @name: Optional alternative iio device name.
+ */
+
+struct ad9523_platform_data {
+	unsigned long vcxo_freq;
+
+	/* Differential/ Single-Ended Input Configuration */
+	bool				refa_diff_rcv_en;
+	bool				refb_diff_rcv_en;
+	bool				zd_in_diff_en;
+	bool				osc_in_diff_en;
+
+	/*
+	 * Valid if differential input disabled
+	 * if false defaults to pos input
+	 */
+	bool				refa_cmos_neg_inp_en;
+	bool				refb_cmos_neg_inp_en;
+	bool				zd_in_cmos_neg_inp_en;
+	bool				osc_in_cmos_neg_inp_en;
+
+	/* PLL1 Setting */
+	unsigned short			refa_r_div;
+	unsigned short			refb_r_div;
+	unsigned short			pll1_feedback_div;
+	unsigned short			pll1_charge_pump_current_nA;
+	bool				zero_delay_mode_internal_en;
+	bool				osc_in_feedback_en;
+	enum pll1_rzero_resistor	pll1_loop_filter_rzero;
+
+	/* Reference */
+	enum ref_sel_mode		ref_mode;
+
+	/* PLL2 Setting */
+	unsigned int			pll2_charge_pump_current_nA;
+	unsigned char			pll2_ndiv_a_cnt;
+	unsigned char			pll2_ndiv_b_cnt;
+	bool				pll2_freq_doubler_en;
+	unsigned char			pll2_r2_div;
+	unsigned char			pll2_vco_diff_m1; /* 3..5 */
+	unsigned char			pll2_vco_diff_m2; /* 3..5 */
+
+	/* Loop Filter PLL2 */
+	enum rpole2_resistor		rpole2;
+	enum rzero_resistor		rzero;
+	enum cpole1_capacitor		cpole1;
+	bool				rzero_bypass_en;
+
+	/* Output Channel Configuration */
+	int				num_channels;
+	struct ad9523_channel_spec	*channels;
+
+	char				name[SPI_NAME_SIZE];
+};
+
+#endif /* IIO_FREQUENCY_AD9523_H_ */