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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: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Gary Bisson 2017-04-25 16:45:17 +02:00 committed by Alexandre Belloni
parent 17e296eb35
commit 1373e77b4f
1 changed files with 172 additions and 0 deletions
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172
drivers/rtc/rtc-m41t80.c
View File

@ -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;
}