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Commit 6c6ff145 authored by Akinobu Mita's avatar Akinobu Mita Committed by Alexandre Belloni
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rtc: ds1307: add clock provider support for DS3231 



DS3231 has programmable square-wave output signal.
This enables to use this feature as a clock provider of
common clock framework.

Signed-off-by: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: default avatarMichael Turquette <mturquette@baylibre.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent f3937549

Documentation/devicetree/bindings/rtc/maxim,ds3231.txt

0 → 100644
+37 −0
Original line number Diff line number Diff line 
* Maxim DS3231 Real Time Clock



Required properties:

see: Documentation/devicetree/bindings/i2c/trivial-devices.txt



Optional property:

- #clock-cells: Should be 1.

- clock-output-names:

  overwrite the default clock names "ds3231_clk_sqw" and "ds3231_clk_32khz".



Each clock is assigned an identifier and client nodes can use this identifier

to specify the clock which they consume. Following indices are allowed:

    - 0: square-wave output on the SQW pin

    - 1: square-wave output on the 32kHz pin



- interrupts: rtc alarm/event interrupt. When this property is selected,

  clock on the SQW pin cannot be used.



Example:



ds3231: ds3231@51 {

	compatible = "maxim,ds3231";

	reg = <0x68>;

	#clock-cells = <1>;

};



device1 {

...

	clocks = <&ds3231 0>;

...

};



device2 {

...

	clocks = <&ds3231 1>;

...

};

drivers/rtc/rtc-ds1307.c

+295 −1
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/string.h>

#include <linux/hwmon.h>

#include <linux/hwmon-sysfs.h>

#include <linux/clk-provider.h>



/*

 * We can't determine type by probing, but if we expect pre-Linux code
@@ -91,6 +92,7 @@ enum ds_type { 
#	define DS1340_BIT_OSF		0x80

#define DS1337_REG_STATUS	0x0f

#	define DS1337_BIT_OSF		0x80

#	define DS3231_BIT_EN32KHZ	0x08

#	define DS1337_BIT_A2I		0x02

#	define DS1337_BIT_A1I		0x01

#define DS1339_REG_ALARM1_SECS	0x07
@@ -120,6 +122,9 @@ struct ds1307 { 
			       u8 length, u8 *values);

	s32 (*write_block_data)(const struct i2c_client *client, u8 command,

				u8 length, const u8 *values);

#ifdef CONFIG_COMMON_CLK

	struct clk_hw		clks[2];

#endif

};



struct chip_desc {
@@ -926,7 +931,295 @@ static void ds1307_hwmon_register(struct ds1307 *ds1307) 
{

}



#endif

#endif /* CONFIG_RTC_DRV_DS1307_HWMON */



/*----------------------------------------------------------------------*/



/*

 * Square-wave output support for DS3231

 * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3231.pdf

 */

#ifdef CONFIG_COMMON_CLK



enum {

	DS3231_CLK_SQW = 0,

	DS3231_CLK_32KHZ,

};



#define clk_sqw_to_ds1307(clk)	\

	container_of(clk, struct ds1307, clks[DS3231_CLK_SQW])

#define clk_32khz_to_ds1307(clk)	\

	container_of(clk, struct ds1307, clks[DS3231_CLK_32KHZ])



static int ds3231_clk_sqw_rates[] = {

	1,

	1024,

	4096,

	8192,

};



static int ds1337_write_control(struct ds1307 *ds1307, u8 mask, u8 value)

{

	struct i2c_client *client = ds1307->client;

	struct mutex *lock = &ds1307->rtc->ops_lock;

	int control;

	int ret;



	mutex_lock(lock);



	control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);

	if (control < 0) {

		ret = control;

		goto out;

	}



	control &= ~mask;

	control |= value;



	ret = i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);

out:

	mutex_unlock(lock);



	return ret;

}



static unsigned long ds3231_clk_sqw_recalc_rate(struct clk_hw *hw,

						unsigned long parent_rate)

{

	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);

	int control;

	int rate_sel = 0;



	control = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_CONTROL);

	if (control < 0)

		return control;

	if (control & DS1337_BIT_RS1)

		rate_sel += 1;

	if (control & DS1337_BIT_RS2)

		rate_sel += 2;



	return ds3231_clk_sqw_rates[rate_sel];

}



static long ds3231_clk_sqw_round_rate(struct clk_hw *hw, unsigned long rate,

					unsigned long *prate)

{

	int i;



	for (i = ARRAY_SIZE(ds3231_clk_sqw_rates) - 1; i >= 0; i--) {

		if (ds3231_clk_sqw_rates[i] <= rate)

			return ds3231_clk_sqw_rates[i];

	}



	return 0;

}



static int ds3231_clk_sqw_set_rate(struct clk_hw *hw, unsigned long rate,

					unsigned long parent_rate)

{

	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);

	int control = 0;

	int rate_sel;



	for (rate_sel = 0; rate_sel < ARRAY_SIZE(ds3231_clk_sqw_rates);

			rate_sel++) {

		if (ds3231_clk_sqw_rates[rate_sel] == rate)

			break;

	}



	if (rate_sel == ARRAY_SIZE(ds3231_clk_sqw_rates))

		return -EINVAL;



	if (rate_sel & 1)

		control |= DS1337_BIT_RS1;

	if (rate_sel & 2)

		control |= DS1337_BIT_RS2;



	return ds1337_write_control(ds1307, DS1337_BIT_RS1 | DS1337_BIT_RS2,

				control);

}



static int ds3231_clk_sqw_prepare(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);



	return ds1337_write_control(ds1307, DS1337_BIT_INTCN, 0);

}



static void ds3231_clk_sqw_unprepare(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);



	ds1337_write_control(ds1307, DS1337_BIT_INTCN, DS1337_BIT_INTCN);

}



static int ds3231_clk_sqw_is_prepared(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);

	int control;



	control = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_CONTROL);

	if (control < 0)

		return control;



	return !(control & DS1337_BIT_INTCN);

}



static const struct clk_ops ds3231_clk_sqw_ops = {

	.prepare = ds3231_clk_sqw_prepare,

	.unprepare = ds3231_clk_sqw_unprepare,

	.is_prepared = ds3231_clk_sqw_is_prepared,

	.recalc_rate = ds3231_clk_sqw_recalc_rate,

	.round_rate = ds3231_clk_sqw_round_rate,

	.set_rate = ds3231_clk_sqw_set_rate,

};



static unsigned long ds3231_clk_32khz_recalc_rate(struct clk_hw *hw,

						unsigned long parent_rate)

{

	return 32768;

}



static int ds3231_clk_32khz_control(struct ds1307 *ds1307, bool enable)

{

	struct i2c_client *client = ds1307->client;

	struct mutex *lock = &ds1307->rtc->ops_lock;

	int status;

	int ret;



	mutex_lock(lock);



	status = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);

	if (status < 0) {

		ret = status;

		goto out;

	}



	if (enable)

		status |= DS3231_BIT_EN32KHZ;

	else

		status &= ~DS3231_BIT_EN32KHZ;



	ret = i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, status);

out:

	mutex_unlock(lock);



	return ret;

}



static int ds3231_clk_32khz_prepare(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);



	return ds3231_clk_32khz_control(ds1307, true);

}



static void ds3231_clk_32khz_unprepare(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);



	ds3231_clk_32khz_control(ds1307, false);

}



static int ds3231_clk_32khz_is_prepared(struct clk_hw *hw)

{

	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);

	int status;



	status = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_STATUS);

	if (status < 0)

		return status;



	return !!(status & DS3231_BIT_EN32KHZ);

}



static const struct clk_ops ds3231_clk_32khz_ops = {

	.prepare = ds3231_clk_32khz_prepare,

	.unprepare = ds3231_clk_32khz_unprepare,

	.is_prepared = ds3231_clk_32khz_is_prepared,

	.recalc_rate = ds3231_clk_32khz_recalc_rate,

};



static struct clk_init_data ds3231_clks_init[] = {

	[DS3231_CLK_SQW] = {

		.name = "ds3231_clk_sqw",

		.ops = &ds3231_clk_sqw_ops,

		.flags = CLK_IS_ROOT,

	},

	[DS3231_CLK_32KHZ] = {

		.name = "ds3231_clk_32khz",

		.ops = &ds3231_clk_32khz_ops,

		.flags = CLK_IS_ROOT,

	},

};



static int ds3231_clks_register(struct ds1307 *ds1307)

{

	struct i2c_client *client = ds1307->client;

	struct device_node *node = client->dev.of_node;

	struct clk_onecell_data	*onecell;

	int i;



	onecell = devm_kzalloc(&client->dev, sizeof(*onecell), GFP_KERNEL);

	if (!onecell)

		return -ENOMEM;



	onecell->clk_num = ARRAY_SIZE(ds3231_clks_init);

	onecell->clks = devm_kcalloc(&client->dev, onecell->clk_num,

					sizeof(onecell->clks[0]), GFP_KERNEL);

	if (!onecell->clks)

		return -ENOMEM;



	for (i = 0; i < ARRAY_SIZE(ds3231_clks_init); i++) {

		struct clk_init_data init = ds3231_clks_init[i];



		/*

		 * Interrupt signal due to alarm conditions and square-wave

		 * output share same pin, so don't initialize both.

		 */

		if (i == DS3231_CLK_SQW && test_bit(HAS_ALARM, &ds1307->flags))

			continue;



		/* optional override of the clockname */

		of_property_read_string_index(node, "clock-output-names", i,

						&init.name);

		ds1307->clks[i].init = &init;



		onecell->clks[i] = devm_clk_register(&client->dev,

							&ds1307->clks[i]);

		if (IS_ERR(onecell->clks[i]))

			return PTR_ERR(onecell->clks[i]);

	}



	if (!node)

		return 0;



	of_clk_add_provider(node, of_clk_src_onecell_get, onecell);



	return 0;

}



static void ds1307_clks_register(struct ds1307 *ds1307)

{

	int ret;



	if (ds1307->type != ds_3231)

		return;



	ret = ds3231_clks_register(ds1307);

	if (ret) {

		dev_warn(&ds1307->client->dev,

			"unable to register clock device %d\n", ret);

	}

}



#else



static void ds1307_clks_register(struct ds1307 *ds1307)

{

}



#endif /* CONFIG_COMMON_CLK */



static int ds1307_probe(struct i2c_client *client,

			const struct i2c_device_id *id)
@@ -1294,6 +1587,7 @@ static int ds1307_probe(struct i2c_client *client, 
	}



	ds1307_hwmon_register(ds1307);

	ds1307_clks_register(ds1307);



	return 0;