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Commit 1373e77b authored by Gary Bisson's avatar Gary Bisson Committed by Alexandre Belloni
Browse files

rtc: m41t80: add clock provider support 



Some devices supported by the m41t80 driver have a programmable
square-wave output signal (see M41T80_FEATURE_SQ).

This enables to use this feature as a clock provider of common
clock framework.

Signed-off-by: default avatarGary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 17e296eb

drivers/rtc/rtc-m41t80.c

+172 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt



#include <linux/bcd.h>

#include <linux/clk-provider.h>

#include <linux/i2c.h>

#include <linux/init.h>

#include <linux/kernel.h>
@@ -53,6 +54,8 @@ 
#define M41T80_ALARM_REG_SIZE	\

	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)



#define M41T80_SQW_MAX_FREQ	32768



#define M41T80_SEC_ST		BIT(7)	/* ST: Stop Bit */

#define M41T80_ALMON_AFE	BIT(7)	/* AFE: AF Enable Bit */

#define M41T80_ALMON_SQWE	BIT(6)	/* SQWE: SQW Enable Bit */
@@ -147,7 +150,11 @@ MODULE_DEVICE_TABLE(of, m41t80_of_match); 


struct m41t80_data {

	unsigned long features;

	struct i2c_client *client;

	struct rtc_device *rtc;

#ifdef CONFIG_COMMON_CLK

	struct clk_hw sqw;

#endif

};



static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
@@ -455,6 +462,166 @@ static struct attribute_group attr_group = { 
	.attrs = attrs,

};



#ifdef CONFIG_COMMON_CLK

#define sqw_to_m41t80_data(_hw) container_of(_hw, struct m41t80_data, sqw)



static unsigned long m41t80_sqw_recalc_rate(struct clk_hw *hw,

					    unsigned long parent_rate)

{

	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);

	struct i2c_client *client = m41t80->client;

	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?

		M41T80_REG_WDAY : M41T80_REG_SQW;

	int ret = i2c_smbus_read_byte_data(client, reg_sqw);

	unsigned long val = M41T80_SQW_MAX_FREQ;



	if (ret < 0)

		return 0;



	ret >>= 4;

	if (ret == 0)

		val = 0;

	else if (ret > 1)

		val = val / (1 << ret);



	return val;

}



static long m41t80_sqw_round_rate(struct clk_hw *hw, unsigned long rate,

				  unsigned long *prate)

{

	int i, freq = M41T80_SQW_MAX_FREQ;



	if (freq <= rate)

		return freq;



	for (i = 2; i <= ilog2(M41T80_SQW_MAX_FREQ); i++) {

		freq /= 1 << i;

		if (freq <= rate)

			return freq;

	}



	return 0;

}



static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate,

			       unsigned long parent_rate)

{

	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);

	struct i2c_client *client = m41t80->client;

	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?

		M41T80_REG_WDAY : M41T80_REG_SQW;

	int reg, ret, val = 0;



	if (rate) {

		if (!is_power_of_2(rate))

			return -EINVAL;

		val = ilog2(rate);

		if (val == ilog2(M41T80_SQW_MAX_FREQ))

			val = 1;

		else if (val < (ilog2(M41T80_SQW_MAX_FREQ) - 1))

			val = ilog2(M41T80_SQW_MAX_FREQ) - val;

		else

			return -EINVAL;

	}



	reg = i2c_smbus_read_byte_data(client, reg_sqw);

	if (reg < 0)

		return reg;



	reg = (reg & 0x0f) | (val << 4);



	ret = i2c_smbus_write_byte_data(client, reg_sqw, reg);

	if (ret < 0)

		return ret;



	return -EINVAL;

}



static int m41t80_sqw_control(struct clk_hw *hw, bool enable)

{

	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);

	struct i2c_client *client = m41t80->client;

	int ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);



	if (ret < 0)

		return ret;



	if (enable)

		ret |= M41T80_ALMON_SQWE;

	else

		ret &= ~M41T80_ALMON_SQWE;



	return i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);

}



static int m41t80_sqw_prepare(struct clk_hw *hw)

{

	return m41t80_sqw_control(hw, 1);

}



static void m41t80_sqw_unprepare(struct clk_hw *hw)

{

	m41t80_sqw_control(hw, 0);

}



static int m41t80_sqw_is_prepared(struct clk_hw *hw)

{

	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);

	struct i2c_client *client = m41t80->client;

	int ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);



	if (ret < 0)

		return ret;



	return !!(ret & M41T80_ALMON_SQWE);

}



static const struct clk_ops m41t80_sqw_ops = {

	.prepare = m41t80_sqw_prepare,

	.unprepare = m41t80_sqw_unprepare,

	.is_prepared = m41t80_sqw_is_prepared,

	.recalc_rate = m41t80_sqw_recalc_rate,

	.round_rate = m41t80_sqw_round_rate,

	.set_rate = m41t80_sqw_set_rate,

};



static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)

{

	struct i2c_client *client = m41t80->client;

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

	struct clk *clk;

	struct clk_init_data init;

	int ret;



	/* First disable the clock */

	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);

	if (ret < 0)

		return ERR_PTR(ret);

	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,

					ret & ~(M41T80_ALMON_SQWE));

	if (ret < 0)

		return ERR_PTR(ret);



	init.name = "m41t80-sqw";

	init.ops = &m41t80_sqw_ops;

	init.flags = 0;

	init.parent_names = NULL;

	init.num_parents = 0;

	m41t80->sqw.init = &init;



	/* optional override of the clockname */

	of_property_read_string(node, "clock-output-names", &init.name);



	/* register the clock */

	clk = clk_register(&client->dev, &m41t80->sqw);

	if (!IS_ERR(clk))

		of_clk_add_provider(node, of_clk_src_simple_get, clk);



	return clk;

}

#endif



#ifdef CONFIG_RTC_DRV_M41T80_WDT

/*

 *****************************************************************************
@@ -772,6 +939,7 @@ static int m41t80_probe(struct i2c_client *client, 
	if (!m41t80_data)

		return -ENOMEM;



	m41t80_data->client = client;

	if (client->dev.of_node)

		m41t80_data->features = (unsigned long)

			of_device_get_match_data(&client->dev);
@@ -863,6 +1031,10 @@ static int m41t80_probe(struct i2c_client *client, 
			return rc;

		}

	}

#endif

#ifdef CONFIG_COMMON_CLK

	if (m41t80_data->features & M41T80_FEATURE_SQ)

		m41t80_sqw_register_clk(m41t80_data);

#endif

	return 0;

}