[PATCH v4] clk: si570: Add a driver for SI570 oscillators

[PATCH v4] clk: si570: Add a driver for SI570 oscillators

[Soren Brinkmann]

Add a driver for SILabs 570, 571, 598, 599 programmable oscillators.
The devices generate low-jitter clock signals and are reprogrammable via
an I2C interface.

Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
---
v4:
 - actually check and handle error on clk_set_rate() call

v3:
 - add delay in the path for small frequency changes, which can take up
   to 100us according to the data sheet
 - use real range for usleep_range() argument
 - use dev_err() over dev_warn() in set_rate()
 - add list of applicable devices for 7ppm DT prop
 - remove comments regarding platform data
 - ignore 7ppm DT prop for incompatible devices
 - replace raw numbers with #defines
 - convert DT prop 'temperature-stability' from boolean to u32
 - make 'temperature-stability' DT prop required (actually not fully
   true, for 59x it is ignored and the driver does not require its
   presence)

v2:
 - document clock-output-names in bindings documentation
 - don't use wildcards in compatibility string
 - change Kconfig entry to "... 570 and compatible devices"
 - change some indentation flaws
 - use 10000 as MIN and MAX value in usleep_range
 - fail probe() if 'factory-fout' is not provided in DT
   - default factory fout #defines removed
 - use i2c driver_data instead of OF data
   - remove some related structs and data
 - rename DT property 'initial-fout' => 'clock-frequency' (like si5351
   driver)
 - add some more details regarding the 'factory-fout' DT property
---
 .../devicetree/bindings/clock/silabs,si570.txt     |  39 ++
 drivers/clk/Kconfig                                |  10 +
 drivers/clk/Makefile                               |   1 +
 drivers/clk/clk-si570.c                            | 536 +++++++++++++++++++++
 4 files changed, 586 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/clock/silabs,si570.txt
 create mode 100644 drivers/clk/clk-si570.c

diff --git a/Documentation/devicetree/bindings/clock/silabs,si570.txt b/Documentation/devicetree/bindings/clock/silabs,si570.txt
new file mode 100644
index 0000000..26aab5c
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/silabs,si570.txt
@@ -0,0 +1,39 @@
+Binding for Silicon Labs 570, 571, 598 and 599 programmable
+I2C clock generators.
+
+Reference
+This binding uses the common clock binding[1]. Details about the devices can be
+found in the data sheets[2][3].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Si570/571 Data Sheet
+    http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
+[3] Si598/599 Data Sheet
+    http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
+
+Required properties:
+ - compatible: Shall be one of "silabs,si570", "silabs,si571",
+			       "silabs,si598", "silabs,si599"
+ - reg: I2C device address.
+ - #clock-cells: From common clock bindings: Shall be 0.
+ - factory-fout: Factory set default frequency. This frequency is part specific.
+		 The correct frequency for the part used has to be provided in
+		 order to generate the correct output frequencies. For more
+		 details, please refer to the data sheet.
+ - temperature-stability: Temperature stability of the device. Should be one of:
+			  7, 20, 50 or 100.
+
+Optional properties:
+ - clock-output-names: From common clock bindings. Recommended to be "si570".
+ - clock-frequency: Output frequency to generate. This defines the output
+		    frequency set during boot. It can be reprogrammed during
+		    runtime through the common clock framework.
+
+Example:
+	si570: clock-generator@5d {
+		#clock-cells = <0>;
+		compatible = "silabs,si570";
+		temperatur-stability = <50>;
+		reg = <0x5d>;
+		factory-fout = <156250000>;
+	};
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 279407a..349b88a 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -64,6 +64,16 @@ config COMMON_CLK_SI5351
 	  This driver supports Silicon Labs 5351A/B/C programmable clock
 	  generators.
 
+config COMMON_CLK_SI570
+	tristate "Clock driver for SiLabs 570 and compatible devices"
+	depends on I2C
+	depends on OF
+	select REGMAP_I2C
+	help
+	---help---
+	  This driver supports Silicon Labs 570/571/598/599 programmable
+	  clock generators.
+
 config COMMON_CLK_S2MPS11
 	tristate "Clock driver for S2MPS11 MFD"
 	depends on MFD_SEC_CORE
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 7b11106..c0e94b3 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_COMMON_CLK_AXI_CLKGEN) += clk-axi-clkgen.o
 obj-$(CONFIG_COMMON_CLK_WM831X) += clk-wm831x.o
 obj-$(CONFIG_COMMON_CLK_MAX77686) += clk-max77686.o
 obj-$(CONFIG_COMMON_CLK_SI5351) += clk-si5351.o
+obj-$(CONFIG_COMMON_CLK_SI570) += clk-si570.o
 obj-$(CONFIG_COMMON_CLK_S2MPS11) += clk-s2mps11.o
 obj-$(CONFIG_CLK_TWL6040)	+= clk-twl6040.o
 obj-$(CONFIG_CLK_PPC_CORENET)	+= clk-ppc-corenet.o
diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
new file mode 100644
index 0000000..13c2091
--- /dev/null
+++ b/drivers/clk/clk-si570.c
@@ -0,0 +1,536 @@
+/*
+ * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
+ *
+ * Copyright (C) 2010, 2011 Ericsson AB.
+ * Copyright (C) 2011 Guenter Roeck.
+ * Copyright (C) 2011 - 2013 Xilinx Inc.
+ *
+ * Author: Guenter Roeck <guenter.roeck@ericsson.com>
+ *	   Sören Brinkmann <soren.brinkmann@xilinx.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/* Si570 registers */
+#define SI570_REG_HS_N1		7
+#define SI570_REG_N1_RFREQ0	8
+#define SI570_REG_RFREQ1	9
+#define SI570_REG_RFREQ2	10
+#define SI570_REG_RFREQ3	11
+#define SI570_REG_RFREQ4	12
+#define SI570_REG_CONTROL	135
+#define SI570_REG_FREEZE_DCO	137
+#define SI570_DIV_OFFSET_7PPM	6
+
+#define HS_DIV_SHIFT		5
+#define HS_DIV_MASK		0xe0
+#define HS_DIV_OFFSET		4
+#define N1_6_2_MASK		0x1f
+#define N1_1_0_MASK		0xc0
+#define RFREQ_37_32_MASK	0x3f
+
+#define SI570_MIN_FREQ		10000000L
+#define SI570_MAX_FREQ		1417500000L
+#define SI598_MAX_FREQ		525000000L
+
+#define FDCO_MIN		4850000000LL
+#define FDCO_MAX		5670000000LL
+
+#define SI570_CNTRL_RECALL	(1 << 0)
+#define SI570_CNTRL_FREEZE_M	(1 << 5)
+#define SI570_CNTRL_NEWFREQ	(1 << 6)
+
+#define SI570_FREEZE_DCO	(1 << 4)
+
+/**
+ * struct clk_si570:
+ * @hw:	Clock hw struct
+ * @regmap:	Device's regmap
+ * @div_offset:	Rgister offset for dividers
+ * @max_freq:	Maximum frequency for this device
+ * @fxtal:	Factory xtal frequency
+ * @n1:		Clock divider N1
+ * @hs_div:	Clock divider HSDIV
+ * @rfreq:	Clock multiplier RFREQ
+ * @frequency:	Current output frequency
+ * @i2c_client:	I2C client pointer
+ */
+struct clk_si570 {
+	struct clk_hw hw;
+	struct regmap *regmap;
+	unsigned int div_offset;
+	u64 max_freq;
+	u64 fxtal;
+	unsigned int n1;
+	unsigned int hs_div;
+	u64 rfreq;
+	u64 frequency;
+	struct i2c_client *i2c_client;
+};
+#define to_clk_si570(_hw)	container_of(_hw, struct clk_si570, hw)
+
+enum clk_si570_variant {
+	si57x,
+	si59x
+};
+
+/**
+ * si570_get_divs() - Read clock dividers from HW
+ * @data:	Pointer to struct clk_si570
+ * @rfreq:	Fractional multiplier (output)
+ * @n1:		Divider N1 (output)
+ * @hs_div:	Divider HSDIV (output)
+ * Returns 0 on success, negative errno otherwise.
+ *
+ * Retrieve clock dividers and multipliers from the HW.
+ */
+static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
+		unsigned int *n1, unsigned int *hs_div)
+{
+	int err;
+	u8 reg[6];
+	u64 tmp;
+
+	err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
+			reg, ARRAY_SIZE(reg));
+	if (err)
+		return err;
+
+	*hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
+	*n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
+	/* Handle invalid cases */
+	if (*n1 > 1)
+		*n1 &= ~1;
+
+	tmp = reg[1] & RFREQ_37_32_MASK;
+	tmp = (tmp << 8) + reg[2];
+	tmp = (tmp << 8) + reg[3];
+	tmp = (tmp << 8) + reg[4];
+	tmp = (tmp << 8) + reg[5];
+	*rfreq = tmp;
+
+	return 0;
+}
+
+/**
+ * si570_get_defaults() - Get default values
+ * @data:	Driver data structure
+ * @fout:	Factory frequency output
+ * Returns 0 on success, negative errno otherwise.
+ */
+static int si570_get_defaults(struct clk_si570 *data, u64 fout)
+{
+	int err;
+	u64 fdco;
+
+	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);
+
+	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
+	if (err)
+		return err;
+
+	/*
+	 * Accept optional precision loss to avoid arithmetic overflows.
+	 * Acceptable per Silicon Labs Application Note AN334.
+	 */
+	fdco = fout * data->n1 * data->hs_div;
+	if (fdco >= (1LL << 36))
+		data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
+	else
+		data->fxtal = div64_u64(fdco << 28, data->rfreq);
+
+	data->frequency = fout;
+
+	return 0;
+}
+
+/**
+ * si570_update_rfreq() - Update clock multiplier
+ * @data:	Driver data structure
+ * Passes on regmap_bulk_write() return value.
+ */
+static int si570_update_rfreq(struct clk_si570 *data)
+{
+	u8 reg[5];
+
+	reg[0] = ((data->n1 - 1) << 6) |
+		((data->rfreq >> 32) & RFREQ_37_32_MASK);
+	reg[1] = (data->rfreq >> 24) & 0xff;
+	reg[2] = (data->rfreq >> 16) & 0xff;
+	reg[3] = (data->rfreq >> 8) & 0xff;
+	reg[4] = data->rfreq & 0xff;
+
+	return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
+			data->div_offset, reg, ARRAY_SIZE(reg));
+}
+
+/**
+ * si570_calc_divs() - Caluclate clock dividers
+ * @frequency:	Target frequency
+ * @data:	Driver data structure
+ * @out_rfreq:	RFREG fractional multiplier (output)
+ * @out_n1:	Clock divider N1 (output)
+ * @out_hs_div:	Clock divider HSDIV (output)
+ * Returns 0 on success, negative errno otherwise.
+ *
+ * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
+ * (@out_rfreq) for a given target @frequency.
+ */
+static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
+		u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
+{
+	int i;
+	unsigned int n1, hs_div;
+	u64 fdco, best_fdco = ULLONG_MAX;
+	static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
+
+	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
+		hs_div = si570_hs_div_values[i];
+		/* Calculate lowest possible value for n1 */
+		n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
+		if (!n1 || (n1 & 1))
+			n1++;
+		while (n1 <= 128) {
+			fdco = (u64)frequency * (u64)hs_div * (u64)n1;
+			if (fdco > FDCO_MAX)
+				break;
+			if (fdco >= FDCO_MIN && fdco < best_fdco) {
+				*out_n1 = n1;
+				*out_hs_div = hs_div;
+				*out_rfreq = div64_u64(fdco << 28, data->fxtal);
+				best_fdco = fdco;
+			}
+			n1 += (n1 == 1 ? 1 : 2);
+		}
+	}
+
+	if (best_fdco == ULLONG_MAX)
+		return -EINVAL;
+
+	return 0;
+}
+
+static unsigned long si570_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	int err;
+	u64 rfreq, rate;
+	unsigned int n1, hs_div;
+	struct clk_si570 *data = to_clk_si570(hw);
+
+	err = si570_get_divs(data, &rfreq, &n1, &hs_div);
+	if (err) {
+		dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
+		return data->frequency;
+	}
+
+	rfreq = div_u64(rfreq, hs_div * n1);
+	rate = (data->fxtal * rfreq) >> 28;
+
+	return rate;
+}
+
+static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
+		unsigned long *parent_rate)
+{
+	int err;
+	u64 rfreq;
+	unsigned int n1, hs_div;
+	struct clk_si570 *data = to_clk_si570(hw);
+
+	if (!rate)
+		return 0;
+
+	if (div64_u64(abs(rate - data->frequency) * 10000LL,
+				data->frequency) < 35) {
+		rfreq = div64_u64((data->rfreq * rate) +
+				div64_u64(data->frequency, 2), data->frequency);
+		n1 = data->n1;
+		hs_div = data->hs_div;
+
+	} else {
+		err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
+		if (err) {
+			dev_err(&data->i2c_client->dev,
+					"unable to round rate\n");
+			return 0;
+		}
+	}
+
+	return rate;
+}
+
+/**
+ * si570_set_frequency() - Adjust output frequency
+ * @data:	Driver data structure
+ * @frequency:	Target frequency
+ * Returns 0 on success.
+ *
+ * Update output frequency for big frequency changes (> 3,500 ppm).
+ */
+static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
+{
+	int err;
+
+	err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
+			&data->hs_div);
+	if (err)
+		return err;
+
+	/*
+	 * The DCO reg should be accessed with a read-modify-write operation
+	 * per AN334
+	 */
+	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
+	regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
+			((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
+			(((data->n1 - 1) >> 2) & N1_6_2_MASK));
+	si570_update_rfreq(data);
+	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
+	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
+
+	/* Applying a new frequency can take up to 10ms */
+	usleep_range(10000, 12000);
+
+	return 0;
+}
+
+/**
+ * si570_set_frequency_small() - Adjust output frequency
+ * @data:	Driver data structure
+ * @frequency:	Target frequency
+ * Returns 0 on success.
+ *
+ * Update output frequency for small frequency changes (< 3,500 ppm).
+ */
+static int si570_set_frequency_small(struct clk_si570 *data,
+				     unsigned long frequency)
+{
+	/*
+	 * This is a re-implementation of DIV_ROUND_CLOSEST
+	 * using the div64_u64 function lieu of letting the compiler
+	 * insert EABI calls
+	 */
+	data->rfreq = div64_u64((data->rfreq * frequency) +
+			div_u64(data->frequency, 2), data->frequency);
+	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
+	si570_update_rfreq(data);
+	regmap_write(data->regmap, SI570_REG_CONTROL, 0);
+
+	/* Applying a new frequency (small change) can take up to 100us */
+	usleep_range(100, 200);
+
+	return 0;
+}
+
+static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
+		unsigned long parent_rate)
+{
+	struct clk_si570 *data = to_clk_si570(hw);
+	struct i2c_client *client = data->i2c_client;
+	int err;
+
+	if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
+		dev_err(&client->dev,
+			"requested frequency %lu Hz is out of range\n", rate);
+		return -EINVAL;
+	}
+
+	if (div64_u64(abs(rate - data->frequency) * 10000LL,
+				data->frequency) < 35)
+		err = si570_set_frequency_small(data, rate);
+	else
+		err = si570_set_frequency(data, rate);
+
+	if (err)
+		return err;
+
+	data->frequency = rate;
+
+	return 0;
+}
+
+static const struct clk_ops si570_clk_ops = {
+	.recalc_rate = si570_recalc_rate,
+	.round_rate = si570_round_rate,
+	.set_rate = si570_set_rate,
+};
+
+static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case SI570_REG_CONTROL:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
+	case SI570_REG_CONTROL:
+	case SI570_REG_FREEZE_DCO:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static struct regmap_config si570_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_RBTREE,
+	.max_register = 137,
+	.writeable_reg = si570_regmap_is_writeable,
+	.volatile_reg = si570_regmap_is_volatile,
+};
+
+static int si570_probe(struct i2c_client *client,
+		const struct i2c_device_id *id)
+{
+	struct clk_si570 *data;
+	struct clk_init_data init;
+	struct clk *clk;
+	u32 initial_fout, factory_fout, stability;
+	int err;
+	enum clk_si570_variant variant = id->driver_data;
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	init.ops = &si570_clk_ops;
+	init.flags = CLK_IS_ROOT;
+	init.num_parents = 0;
+	data->hw.init = &init;
+	data->i2c_client = client;
+
+	if (variant == si57x) {
+		err = of_property_read_u32(client->dev.of_node,
+				"temperature-stability", &stability);
+		if (err) {
+			dev_err(&client->dev,
+				  "'temperature-stability' property missing\n");
+			return err;
+		}
+		/* adjust register offsets for 7ppm devices */
+		if (stability == 7)
+			data->div_offset = SI570_DIV_OFFSET_7PPM;
+
+		data->max_freq = SI570_MAX_FREQ;
+	} else {
+		data->max_freq = SI598_MAX_FREQ;
+	}
+
+	if (of_property_read_string(client->dev.of_node, "clock-output-names",
+			&init.name))
+		init.name = client->dev.of_node->name;
+
+	err = of_property_read_u32(client->dev.of_node, "factory-fout",
+			&factory_fout);
+	if (err) {
+		dev_err(&client->dev, "'factory-fout' property missing\n");
+		return err;
+	}
+
+	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(&client->dev, "failed to allocate register map\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	i2c_set_clientdata(client, data);
+	err = si570_get_defaults(data, factory_fout);
+	if (err)
+		return err;
+
+	clk = devm_clk_register(&client->dev, &data->hw);
+	if (IS_ERR(clk)) {
+		dev_err(&client->dev, "clock registration failed\n");
+		return PTR_ERR(clk);
+	}
+	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
+			clk);
+	if (err) {
+		dev_err(&client->dev, "unable to add clk provider\n");
+		return err;
+	}
+
+	/* Read the requested initial output frequency from device tree */
+	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
+				&initial_fout)) {
+		err = clk_set_rate(clk, initial_fout);
+		if (err) {
+			of_clk_del_provider(client->dev.of_node);
+			clk_unregister(data->hw.clk);
+			return err;
+		}
+	}
+
+	/* Display a message indicating that we've successfully registered */
+	dev_info(&client->dev, "registered, current frequency %llu Hz\n",
+			data->frequency);
+
+	return 0;
+}
+
+static int si570_remove(struct i2c_client *client)
+{
+	struct clk_si570 *data = i2c_get_clientdata(client);
+
+	of_clk_del_provider(client->dev.of_node);
+	clk_unregister(data->hw.clk);
+
+	return 0;
+}
+
+static const struct i2c_device_id si570_id[] = {
+	{ "si570", si57x },
+	{ "si571", si57x },
+	{ "si598", si59x },
+	{ "si599", si59x },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si570_id);
+
+static const struct of_device_id clk_si570_of_match[] = {
+	{ .compatible = "silabs,si570" },
+	{ .compatible = "silabs,si571" },
+	{ .compatible = "silabs,si598" },
+	{ .compatible = "silabs,si599" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, clk_si570_of_match);
+
+static struct i2c_driver si570_driver = {
+	.driver = {
+		.name = "si570",
+		.of_match_table = of_match_ptr(clk_si570_of_match),
+	},
+	.probe		= si570_probe,
+	.remove		= si570_remove,
+	.id_table	= si570_id,
+};
+module_i2c_driver(si570_driver);
+
+MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
+MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com");
+MODULE_DESCRIPTION("Si570 driver");
+MODULE_LICENSE("GPL");
-- 
1.8.4

Re: [PATCH v4] clk: si570: Add a driver for SI570 oscillators

[Guenter Roeck]

On Fri, Sep 20, 2013 at 10:39:17AM -0700, Soren Brinkmann wrote:
> Add a driver for SILabs 570, 571, 598, 599 programmable oscillators.
> The devices generate low-jitter clock signals and are reprogrammable via
> an I2C interface.
> 
> Cc: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
> Signed-off-by: Soren Brinkmann <soren.brinkmann-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org>
> ---
> v4:
>  - actually check and handle error on clk_set_rate() call
> 
> v3:
>  - add delay in the path for small frequency changes, which can take up
>    to 100us according to the data sheet
>  - use real range for usleep_range() argument
>  - use dev_err() over dev_warn() in set_rate()
>  - add list of applicable devices for 7ppm DT prop
>  - remove comments regarding platform data
>  - ignore 7ppm DT prop for incompatible devices
>  - replace raw numbers with #defines
>  - convert DT prop 'temperature-stability' from boolean to u32
>  - make 'temperature-stability' DT prop required (actually not fully
>    true, for 59x it is ignored and the driver does not require its
>    presence)
> 
> v2:
>  - document clock-output-names in bindings documentation
>  - don't use wildcards in compatibility string
>  - change Kconfig entry to "... 570 and compatible devices"
>  - change some indentation flaws
>  - use 10000 as MIN and MAX value in usleep_range
>  - fail probe() if 'factory-fout' is not provided in DT
>    - default factory fout #defines removed
>  - use i2c driver_data instead of OF data
>    - remove some related structs and data
>  - rename DT property 'initial-fout' => 'clock-frequency' (like si5351
>    driver)
>  - add some more details regarding the 'factory-fout' DT property
> ---
>  .../devicetree/bindings/clock/silabs,si570.txt     |  39 ++
>  drivers/clk/Kconfig                                |  10 +
>  drivers/clk/Makefile                               |   1 +
>  drivers/clk/clk-si570.c                            | 536 +++++++++++++++++++++
>  4 files changed, 586 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/clock/silabs,si570.txt
>  create mode 100644 drivers/clk/clk-si570.c
> 
> diff --git a/Documentation/devicetree/bindings/clock/silabs,si570.txt b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> new file mode 100644
> index 0000000..26aab5c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> @@ -0,0 +1,39 @@
> +Binding for Silicon Labs 570, 571, 598 and 599 programmable
> +I2C clock generators.
> +
> +Reference
> +This binding uses the common clock binding[1]. Details about the devices can be
> +found in the data sheets[2][3].
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +[2] Si570/571 Data Sheet
> +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
> +[3] Si598/599 Data Sheet
> +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
> +
> +Required properties:
> + - compatible: Shall be one of "silabs,si570", "silabs,si571",
> +			       "silabs,si598", "silabs,si599"
> + - reg: I2C device address.
> + - #clock-cells: From common clock bindings: Shall be 0.
> + - factory-fout: Factory set default frequency. This frequency is part specific.
> +		 The correct frequency for the part used has to be provided in
> +		 order to generate the correct output frequencies. For more
> +		 details, please refer to the data sheet.
> + - temperature-stability: Temperature stability of the device. Should be one of:
> +			  7, 20, 50 or 100.
> +
It might make sense to specify that this is in microseconds.

> +Optional properties:
> + - clock-output-names: From common clock bindings. Recommended to be "si570".
> + - clock-frequency: Output frequency to generate. This defines the output
> +		    frequency set during boot. It can be reprogrammed during
> +		    runtime through the common clock framework.
> +
> +Example:
> +	si570: clock-generator@5d {
> +		#clock-cells = <0>;
> +		compatible = "silabs,si570";
> +		temperatur-stability = <50>;

temperature

> +		reg = <0x5d>;
> +		factory-fout = <156250000>;
> +	};
> diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
> index 279407a..349b88a 100644
> --- a/drivers/clk/Kconfig
> +++ b/drivers/clk/Kconfig
> @@ -64,6 +64,16 @@ config COMMON_CLK_SI5351
>  	  This driver supports Silicon Labs 5351A/B/C programmable clock
>  	  generators.
>  
> +config COMMON_CLK_SI570
> +	tristate "Clock driver for SiLabs 570 and compatible devices"
> +	depends on I2C
> +	depends on OF
> +	select REGMAP_I2C
> +	help
> +	---help---
> +	  This driver supports Silicon Labs 570/571/598/599 programmable
> +	  clock generators.
> +
>  config COMMON_CLK_S2MPS11
>  	tristate "Clock driver for S2MPS11 MFD"
>  	depends on MFD_SEC_CORE
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index 7b11106..c0e94b3 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -40,6 +40,7 @@ obj-$(CONFIG_COMMON_CLK_AXI_CLKGEN) += clk-axi-clkgen.o
>  obj-$(CONFIG_COMMON_CLK_WM831X) += clk-wm831x.o
>  obj-$(CONFIG_COMMON_CLK_MAX77686) += clk-max77686.o
>  obj-$(CONFIG_COMMON_CLK_SI5351) += clk-si5351.o
> +obj-$(CONFIG_COMMON_CLK_SI570) += clk-si570.o
>  obj-$(CONFIG_COMMON_CLK_S2MPS11) += clk-s2mps11.o
>  obj-$(CONFIG_CLK_TWL6040)	+= clk-twl6040.o
>  obj-$(CONFIG_CLK_PPC_CORENET)	+= clk-ppc-corenet.o
> diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
> new file mode 100644
> index 0000000..13c2091
> --- /dev/null
> +++ b/drivers/clk/clk-si570.c
> @@ -0,0 +1,536 @@
> +/*
> + * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
> + *
> + * Copyright (C) 2010, 2011 Ericsson AB.
> + * Copyright (C) 2011 Guenter Roeck.
> + * Copyright (C) 2011 - 2013 Xilinx Inc.
> + *
> + * Author: Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org>
> + *	   Sören Brinkmann <soren.brinkmann-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +/* Si570 registers */
> +#define SI570_REG_HS_N1		7
> +#define SI570_REG_N1_RFREQ0	8
> +#define SI570_REG_RFREQ1	9
> +#define SI570_REG_RFREQ2	10
> +#define SI570_REG_RFREQ3	11
> +#define SI570_REG_RFREQ4	12
> +#define SI570_REG_CONTROL	135
> +#define SI570_REG_FREEZE_DCO	137
> +#define SI570_DIV_OFFSET_7PPM	6
> +
> +#define HS_DIV_SHIFT		5
> +#define HS_DIV_MASK		0xe0
> +#define HS_DIV_OFFSET		4
> +#define N1_6_2_MASK		0x1f
> +#define N1_1_0_MASK		0xc0
> +#define RFREQ_37_32_MASK	0x3f
> +
> +#define SI570_MIN_FREQ		10000000L
> +#define SI570_MAX_FREQ		1417500000L
> +#define SI598_MAX_FREQ		525000000L
> +
> +#define FDCO_MIN		4850000000LL
> +#define FDCO_MAX		5670000000LL
> +
> +#define SI570_CNTRL_RECALL	(1 << 0)
> +#define SI570_CNTRL_FREEZE_M	(1 << 5)
> +#define SI570_CNTRL_NEWFREQ	(1 << 6)
> +
> +#define SI570_FREEZE_DCO	(1 << 4)
> +
> +/**
> + * struct clk_si570:
> + * @hw:	Clock hw struct
> + * @regmap:	Device's regmap
> + * @div_offset:	Rgister offset for dividers
> + * @max_freq:	Maximum frequency for this device
> + * @fxtal:	Factory xtal frequency
> + * @n1:		Clock divider N1
> + * @hs_div:	Clock divider HSDIV
> + * @rfreq:	Clock multiplier RFREQ
> + * @frequency:	Current output frequency
> + * @i2c_client:	I2C client pointer
> + */
> +struct clk_si570 {
> +	struct clk_hw hw;
> +	struct regmap *regmap;
> +	unsigned int div_offset;
> +	u64 max_freq;
> +	u64 fxtal;
> +	unsigned int n1;
> +	unsigned int hs_div;
> +	u64 rfreq;
> +	u64 frequency;
> +	struct i2c_client *i2c_client;
> +};
> +#define to_clk_si570(_hw)	container_of(_hw, struct clk_si570, hw)
> +
> +enum clk_si570_variant {
> +	si57x,
> +	si59x
> +};
> +
> +/**
> + * si570_get_divs() - Read clock dividers from HW
> + * @data:	Pointer to struct clk_si570
> + * @rfreq:	Fractional multiplier (output)
> + * @n1:		Divider N1 (output)
> + * @hs_div:	Divider HSDIV (output)
> + * Returns 0 on success, negative errno otherwise.
> + *
> + * Retrieve clock dividers and multipliers from the HW.
> + */
> +static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
> +		unsigned int *n1, unsigned int *hs_div)
> +{
> +	int err;
> +	u8 reg[6];
> +	u64 tmp;
> +
> +	err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
> +			reg, ARRAY_SIZE(reg));
> +	if (err)
> +		return err;
> +
> +	*hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
> +	*n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
> +	/* Handle invalid cases */
> +	if (*n1 > 1)
> +		*n1 &= ~1;
> +
> +	tmp = reg[1] & RFREQ_37_32_MASK;
> +	tmp = (tmp << 8) + reg[2];
> +	tmp = (tmp << 8) + reg[3];
> +	tmp = (tmp << 8) + reg[4];
> +	tmp = (tmp << 8) + reg[5];
> +	*rfreq = tmp;
> +
> +	return 0;
> +}
> +
> +/**
> + * si570_get_defaults() - Get default values
> + * @data:	Driver data structure
> + * @fout:	Factory frequency output
> + * Returns 0 on success, negative errno otherwise.
> + */
> +static int si570_get_defaults(struct clk_si570 *data, u64 fout)
> +{
> +	int err;
> +	u64 fdco;
> +
> +	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);
> +
> +	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * Accept optional precision loss to avoid arithmetic overflows.
> +	 * Acceptable per Silicon Labs Application Note AN334.
> +	 */
> +	fdco = fout * data->n1 * data->hs_div;
> +	if (fdco >= (1LL << 36))
> +		data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
> +	else
> +		data->fxtal = div64_u64(fdco << 28, data->rfreq);
> +
> +	data->frequency = fout;
> +
> +	return 0;
> +}
> +
> +/**
> + * si570_update_rfreq() - Update clock multiplier
> + * @data:	Driver data structure
> + * Passes on regmap_bulk_write() return value.
> + */
> +static int si570_update_rfreq(struct clk_si570 *data)
> +{
> +	u8 reg[5];
> +
> +	reg[0] = ((data->n1 - 1) << 6) |
> +		((data->rfreq >> 32) & RFREQ_37_32_MASK);
> +	reg[1] = (data->rfreq >> 24) & 0xff;
> +	reg[2] = (data->rfreq >> 16) & 0xff;
> +	reg[3] = (data->rfreq >> 8) & 0xff;
> +	reg[4] = data->rfreq & 0xff;
> +
> +	return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
> +			data->div_offset, reg, ARRAY_SIZE(reg));
> +}
> +
> +/**
> + * si570_calc_divs() - Caluclate clock dividers
> + * @frequency:	Target frequency
> + * @data:	Driver data structure
> + * @out_rfreq:	RFREG fractional multiplier (output)
> + * @out_n1:	Clock divider N1 (output)
> + * @out_hs_div:	Clock divider HSDIV (output)
> + * Returns 0 on success, negative errno otherwise.
> + *
> + * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
> + * (@out_rfreq) for a given target @frequency.
> + */
> +static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
> +		u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
> +{
> +	int i;
> +	unsigned int n1, hs_div;
> +	u64 fdco, best_fdco = ULLONG_MAX;
> +	static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
> +
> +	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
> +		hs_div = si570_hs_div_values[i];
> +		/* Calculate lowest possible value for n1 */
> +		n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
> +		if (!n1 || (n1 & 1))
> +			n1++;
> +		while (n1 <= 128) {
> +			fdco = (u64)frequency * (u64)hs_div * (u64)n1;
> +			if (fdco > FDCO_MAX)
> +				break;
> +			if (fdco >= FDCO_MIN && fdco < best_fdco) {
> +				*out_n1 = n1;
> +				*out_hs_div = hs_div;
> +				*out_rfreq = div64_u64(fdco << 28, data->fxtal);
> +				best_fdco = fdco;
> +			}
> +			n1 += (n1 == 1 ? 1 : 2);
> +		}
> +	}
> +
> +	if (best_fdco == ULLONG_MAX)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static unsigned long si570_recalc_rate(struct clk_hw *hw,
> +		unsigned long parent_rate)
> +{
> +	int err;
> +	u64 rfreq, rate;
> +	unsigned int n1, hs_div;
> +	struct clk_si570 *data = to_clk_si570(hw);
> +
> +	err = si570_get_divs(data, &rfreq, &n1, &hs_div);
> +	if (err) {
> +		dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
> +		return data->frequency;
> +	}
> +
> +	rfreq = div_u64(rfreq, hs_div * n1);
> +	rate = (data->fxtal * rfreq) >> 28;
> +
> +	return rate;
> +}
> +
> +static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
> +		unsigned long *parent_rate)
> +{
> +	int err;
> +	u64 rfreq;
> +	unsigned int n1, hs_div;
> +	struct clk_si570 *data = to_clk_si570(hw);
> +
> +	if (!rate)
> +		return 0;
> +
> +	if (div64_u64(abs(rate - data->frequency) * 10000LL,
> +				data->frequency) < 35) {
> +		rfreq = div64_u64((data->rfreq * rate) +
> +				div64_u64(data->frequency, 2), data->frequency);
> +		n1 = data->n1;
> +		hs_div = data->hs_div;
> +
> +	} else {
> +		err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
> +		if (err) {
> +			dev_err(&data->i2c_client->dev,
> +					"unable to round rate\n");
> +			return 0;
> +		}
> +	}
> +
> +	return rate;
> +}
> +
> +/**
> + * si570_set_frequency() - Adjust output frequency
> + * @data:	Driver data structure
> + * @frequency:	Target frequency
> + * Returns 0 on success.
> + *
> + * Update output frequency for big frequency changes (> 3,500 ppm).
> + */
> +static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
> +{
> +	int err;
> +
> +	err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
> +			&data->hs_div);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * The DCO reg should be accessed with a read-modify-write operation
> +	 * per AN334
> +	 */
> +	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
> +	regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
> +			((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
> +			(((data->n1 - 1) >> 2) & N1_6_2_MASK));
> +	si570_update_rfreq(data);
> +	regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
> +	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
> +
> +	/* Applying a new frequency can take up to 10ms */
> +	usleep_range(10000, 12000);
> +
> +	return 0;
> +}
> +
> +/**
> + * si570_set_frequency_small() - Adjust output frequency
> + * @data:	Driver data structure
> + * @frequency:	Target frequency
> + * Returns 0 on success.
> + *
> + * Update output frequency for small frequency changes (< 3,500 ppm).
> + */
> +static int si570_set_frequency_small(struct clk_si570 *data,
> +				     unsigned long frequency)
> +{
> +	/*
> +	 * This is a re-implementation of DIV_ROUND_CLOSEST
> +	 * using the div64_u64 function lieu of letting the compiler
> +	 * insert EABI calls
> +	 */
> +	data->rfreq = div64_u64((data->rfreq * frequency) +
> +			div_u64(data->frequency, 2), data->frequency);
> +	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
> +	si570_update_rfreq(data);
> +	regmap_write(data->regmap, SI570_REG_CONTROL, 0);
> +
> +	/* Applying a new frequency (small change) can take up to 100us */
> +	usleep_range(100, 200);
> +
> +	return 0;
> +}
> +
> +static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
> +		unsigned long parent_rate)
> +{
> +	struct clk_si570 *data = to_clk_si570(hw);
> +	struct i2c_client *client = data->i2c_client;
> +	int err;
> +
> +	if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
> +		dev_err(&client->dev,
> +			"requested frequency %lu Hz is out of range\n", rate);
> +		return -EINVAL;
> +	}
> +
> +	if (div64_u64(abs(rate - data->frequency) * 10000LL,
> +				data->frequency) < 35)
> +		err = si570_set_frequency_small(data, rate);
> +	else
> +		err = si570_set_frequency(data, rate);
> +
> +	if (err)
> +		return err;
> +
> +	data->frequency = rate;
> +
> +	return 0;
> +}
> +
> +static const struct clk_ops si570_clk_ops = {
> +	.recalc_rate = si570_recalc_rate,
> +	.round_rate = si570_round_rate,
> +	.set_rate = si570_set_rate,
> +};
> +
> +static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case SI570_REG_CONTROL:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
> +	case SI570_REG_CONTROL:
> +	case SI570_REG_FREEZE_DCO:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static struct regmap_config si570_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.cache_type = REGCACHE_RBTREE,
> +	.max_register = 137,
> +	.writeable_reg = si570_regmap_is_writeable,
> +	.volatile_reg = si570_regmap_is_volatile,
> +};
> +
> +static int si570_probe(struct i2c_client *client,
> +		const struct i2c_device_id *id)
> +{
> +	struct clk_si570 *data;
> +	struct clk_init_data init;
> +	struct clk *clk;
> +	u32 initial_fout, factory_fout, stability;
> +	int err;
> +	enum clk_si570_variant variant = id->driver_data;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	init.ops = &si570_clk_ops;
> +	init.flags = CLK_IS_ROOT;
> +	init.num_parents = 0;
> +	data->hw.init = &init;
> +	data->i2c_client = client;
> +
> +	if (variant == si57x) {
> +		err = of_property_read_u32(client->dev.of_node,
> +				"temperature-stability", &stability);
> +		if (err) {
> +			dev_err(&client->dev,
> +				  "'temperature-stability' property missing\n");
> +			return err;
> +		}
> +		/* adjust register offsets for 7ppm devices */
> +		if (stability == 7)
> +			data->div_offset = SI570_DIV_OFFSET_7PPM;
> +
> +		data->max_freq = SI570_MAX_FREQ;
> +	} else {
> +		data->max_freq = SI598_MAX_FREQ;
> +	}
> +
> +	if (of_property_read_string(client->dev.of_node, "clock-output-names",
> +			&init.name))
> +		init.name = client->dev.of_node->name;
> +
> +	err = of_property_read_u32(client->dev.of_node, "factory-fout",
> +			&factory_fout);
> +	if (err) {
> +		dev_err(&client->dev, "'factory-fout' property missing\n");
> +		return err;
> +	}
> +
> +	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
> +	if (IS_ERR(data->regmap)) {
> +		dev_err(&client->dev, "failed to allocate register map\n");
> +		return PTR_ERR(data->regmap);
> +	}
> +
> +	i2c_set_clientdata(client, data);
> +	err = si570_get_defaults(data, factory_fout);
> +	if (err)
> +		return err;
> +
> +	clk = devm_clk_register(&client->dev, &data->hw);
> +	if (IS_ERR(clk)) {
> +		dev_err(&client->dev, "clock registration failed\n");
> +		return PTR_ERR(clk);
> +	}
> +	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
> +			clk);
> +	if (err) {
> +		dev_err(&client->dev, "unable to add clk provider\n");
> +		return err;
> +	}
> +
> +	/* Read the requested initial output frequency from device tree */
> +	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
> +				&initial_fout)) {
> +		err = clk_set_rate(clk, initial_fout);
> +		if (err) {
> +			of_clk_del_provider(client->dev.of_node);
> +			clk_unregister(data->hw.clk);

Is that needed ? I would have thought it isn't because you use a devm_ function
to register it.

Not that I understand the clk code, but getting clk from the registration
function and unregistering hw.clk (without seting it) sems a bit odd.
Is it well defined that you have to unregister hw.clk ?

> +			return err;
> +		}
> +	}
> +
> +	/* Display a message indicating that we've successfully registered */
> +	dev_info(&client->dev, "registered, current frequency %llu Hz\n",
> +			data->frequency);
> +
> +	return 0;
> +}
> +
> +static int si570_remove(struct i2c_client *client)
> +{
> +	struct clk_si570 *data = i2c_get_clientdata(client);
> +
> +	of_clk_del_provider(client->dev.of_node);
> +	clk_unregister(data->hw.clk);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id si570_id[] = {
> +	{ "si570", si57x },
> +	{ "si571", si57x },
> +	{ "si598", si59x },
> +	{ "si599", si59x },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, si570_id);
> +
> +static const struct of_device_id clk_si570_of_match[] = {
> +	{ .compatible = "silabs,si570" },
> +	{ .compatible = "silabs,si571" },
> +	{ .compatible = "silabs,si598" },
> +	{ .compatible = "silabs,si599" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, clk_si570_of_match);
> +
> +static struct i2c_driver si570_driver = {
> +	.driver = {
> +		.name = "si570",
> +		.of_match_table = of_match_ptr(clk_si570_of_match),
> +	},
> +	.probe		= si570_probe,
> +	.remove		= si570_remove,
> +	.id_table	= si570_id,
> +};
> +module_i2c_driver(si570_driver);
> +
> +MODULE_AUTHOR("Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org>");
> +MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org");
> +MODULE_DESCRIPTION("Si570 driver");
> +MODULE_LICENSE("GPL");
> -- 
> 1.8.4
> 
> 
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Re: [PATCH v4] clk: si570: Add a driver for SI570 oscillators

[Sören Brinkmann]

On Fri, Sep 20, 2013 at 11:15:29AM -0700, Guenter Roeck wrote:
> On Fri, Sep 20, 2013 at 10:39:17AM -0700, Soren Brinkmann wrote:
> > Add a driver for SILabs 570, 571, 598, 599 programmable oscillators.
> > The devices generate low-jitter clock signals and are reprogrammable via
> > an I2C interface.
> > 
> > Cc: Guenter Roeck <linux@roeck-us.net>
> > Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
> > ---
> > v4:
> >  - actually check and handle error on clk_set_rate() call
> > 
> > v3:
> >  - add delay in the path for small frequency changes, which can take up
> >    to 100us according to the data sheet
> >  - use real range for usleep_range() argument
> >  - use dev_err() over dev_warn() in set_rate()
> >  - add list of applicable devices for 7ppm DT prop
> >  - remove comments regarding platform data
> >  - ignore 7ppm DT prop for incompatible devices
> >  - replace raw numbers with #defines
> >  - convert DT prop 'temperature-stability' from boolean to u32
> >  - make 'temperature-stability' DT prop required (actually not fully
> >    true, for 59x it is ignored and the driver does not require its
> >    presence)
> > 
> > v2:
> >  - document clock-output-names in bindings documentation
> >  - don't use wildcards in compatibility string
> >  - change Kconfig entry to "... 570 and compatible devices"
> >  - change some indentation flaws
> >  - use 10000 as MIN and MAX value in usleep_range
> >  - fail probe() if 'factory-fout' is not provided in DT
> >    - default factory fout #defines removed
> >  - use i2c driver_data instead of OF data
> >    - remove some related structs and data
> >  - rename DT property 'initial-fout' => 'clock-frequency' (like si5351
> >    driver)
> >  - add some more details regarding the 'factory-fout' DT property
> > ---
> >  .../devicetree/bindings/clock/silabs,si570.txt     |  39 ++
> >  drivers/clk/Kconfig                                |  10 +
> >  drivers/clk/Makefile                               |   1 +
> >  drivers/clk/clk-si570.c                            | 536 +++++++++++++++++++++
> >  4 files changed, 586 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/clock/silabs,si570.txt
> >  create mode 100644 drivers/clk/clk-si570.c
> > 
> > diff --git a/Documentation/devicetree/bindings/clock/silabs,si570.txt b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> > new file mode 100644
> > index 0000000..26aab5c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> > @@ -0,0 +1,39 @@
> > +Binding for Silicon Labs 570, 571, 598 and 599 programmable
> > +I2C clock generators.
> > +
> > +Reference
> > +This binding uses the common clock binding[1]. Details about the devices can be
> > +found in the data sheets[2][3].
> > +
> > +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> > +[2] Si570/571 Data Sheet
> > +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
> > +[3] Si598/599 Data Sheet
> > +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
> > +
> > +Required properties:
> > + - compatible: Shall be one of "silabs,si570", "silabs,si571",
> > +			       "silabs,si598", "silabs,si599"
> > + - reg: I2C device address.
> > + - #clock-cells: From common clock bindings: Shall be 0.
> > + - factory-fout: Factory set default frequency. This frequency is part specific.
> > +		 The correct frequency for the part used has to be provided in
> > +		 order to generate the correct output frequencies. For more
> > +		 details, please refer to the data sheet.
> > + - temperature-stability: Temperature stability of the device. Should be one of:
> > +			  7, 20, 50 or 100.
> > +
> It might make sense to specify that this is in microseconds.
ppm, but yes giving the unit is a good idea.

> 
> > +Optional properties:
> > + - clock-output-names: From common clock bindings. Recommended to be "si570".
> > + - clock-frequency: Output frequency to generate. This defines the output
> > +		    frequency set during boot. It can be reprogrammed during
> > +		    runtime through the common clock framework.
> > +
> > +Example:
> > +	si570: clock-generator@5d {
> > +		#clock-cells = <0>;
> > +		compatible = "silabs,si570";
> > +		temperatur-stability = <50>;
> 
> temperature
damn typos.

> 
> > +		reg = <0x5d>;
> > +		factory-fout = <156250000>;
> > +	};
[...]
> > diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
> > new file mode 100644
> > index 0000000..13c2091
> > --- /dev/null
> > +++ b/drivers/clk/clk-si570.c
[...]
> > +static int si570_probe(struct i2c_client *client,
> > +		const struct i2c_device_id *id)
> > +{
> > +	struct clk_si570 *data;
> > +	struct clk_init_data init;
> > +	struct clk *clk;
> > +	u32 initial_fout, factory_fout, stability;
> > +	int err;
> > +	enum clk_si570_variant variant = id->driver_data;
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	init.ops = &si570_clk_ops;
> > +	init.flags = CLK_IS_ROOT;
> > +	init.num_parents = 0;
> > +	data->hw.init = &init;
> > +	data->i2c_client = client;
> > +
> > +	if (variant == si57x) {
> > +		err = of_property_read_u32(client->dev.of_node,
> > +				"temperature-stability", &stability);
> > +		if (err) {
> > +			dev_err(&client->dev,
> > +				  "'temperature-stability' property missing\n");
> > +			return err;
> > +		}
> > +		/* adjust register offsets for 7ppm devices */
> > +		if (stability == 7)
> > +			data->div_offset = SI570_DIV_OFFSET_7PPM;
> > +
> > +		data->max_freq = SI570_MAX_FREQ;
> > +	} else {
> > +		data->max_freq = SI598_MAX_FREQ;
> > +	}
> > +
> > +	if (of_property_read_string(client->dev.of_node, "clock-output-names",
> > +			&init.name))
> > +		init.name = client->dev.of_node->name;
> > +
> > +	err = of_property_read_u32(client->dev.of_node, "factory-fout",
> > +			&factory_fout);
> > +	if (err) {
> > +		dev_err(&client->dev, "'factory-fout' property missing\n");
> > +		return err;
> > +	}
> > +
> > +	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
> > +	if (IS_ERR(data->regmap)) {
> > +		dev_err(&client->dev, "failed to allocate register map\n");
> > +		return PTR_ERR(data->regmap);
> > +	}
> > +
> > +	i2c_set_clientdata(client, data);
> > +	err = si570_get_defaults(data, factory_fout);
> > +	if (err)
> > +		return err;
> > +
> > +	clk = devm_clk_register(&client->dev, &data->hw);
> > +	if (IS_ERR(clk)) {
> > +		dev_err(&client->dev, "clock registration failed\n");
> > +		return PTR_ERR(clk);
> > +	}
> > +	err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
> > +			clk);
> > +	if (err) {
> > +		dev_err(&client->dev, "unable to add clk provider\n");
> > +		return err;
> > +	}
> > +
> > +	/* Read the requested initial output frequency from device tree */
> > +	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
> > +				&initial_fout)) {
> > +		err = clk_set_rate(clk, initial_fout);
> > +		if (err) {
> > +			of_clk_del_provider(client->dev.of_node);
> > +			clk_unregister(data->hw.clk);
> 
> Is that needed ? I would have thought it isn't because you use a devm_ function
> to register it.
> 
> Not that I understand the clk code, but getting clk from the registration
> function and unregistering hw.clk (without seting it) sems a bit odd.
> Is it well defined that you have to unregister hw.clk ?
I have to double check. I thought the managed interface is only saving
you a call to clk_put() but I may be wrong.

	Sören

Re: [PATCH v4] clk: si570: Add a driver for SI570 oscillators

[Sören Brinkmann]

On Fri, Sep 20, 2013 at 11:15:29AM -0700, Guenter Roeck wrote:
> On Fri, Sep 20, 2013 at 10:39:17AM -0700, Soren Brinkmann wrote:
[...]
> > diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
> > new file mode 100644
> > index 0000000..13c2091
> > --- /dev/null
> > +++ b/drivers/clk/clk-si570.c
[...]
> > +static int si570_probe(struct i2c_client *client,
[...]
> > +	/* Read the requested initial output frequency from device tree */
> > +	if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
> > +				&initial_fout)) {
> > +		err = clk_set_rate(clk, initial_fout);
> > +		if (err) {
> > +			of_clk_del_provider(client->dev.of_node);
> > +			clk_unregister(data->hw.clk);
> 
> Is that needed ? I would have thought it isn't because you use a devm_ function
> to register it.
> 
> Not that I understand the clk code, but getting clk from the registration
> function and unregistering hw.clk (without seting it) sems a bit odd.
> Is it well defined that you have to unregister hw.clk ?
You're absolutely right. I'll remove all calls to clk_unregister().
Thanks for finding that one.

	Sören


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