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Date: Tue, 25 Apr 2017 16:45:17 +0200
From: Gary Bisson <gary.bisson@...ndarydevices.com>
To: rtc-linux@...glegroups.com
Cc: linux-kernel@...r.kernel.org, alexandre.belloni@...e-electrons.com,
a.zummo@...ertech.it, Gary Bisson <gary.bisson@...ndarydevices.com>
Subject: [PATCH 4/4] 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@...ndarydevices.com>
---
drivers/rtc/rtc-m41t80.c | 172 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 172 insertions(+)
diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 2bdf494a9bd4..ea3d1efe9192 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -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>
@@ -52,6 +53,8 @@
#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 */
@@ -88,7 +91,11 @@ MODULE_DEVICE_TABLE(i2c, m41t80_id);
struct m41t80_data {
u8 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)
@@ -396,6 +403,166 @@ 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
/*
*****************************************************************************
@@ -713,6 +880,7 @@ static int m41t80_probe(struct i2c_client *client,
if (!m41t80_data)
return -ENOMEM;
+ m41t80_data->client = client;
m41t80_data->features = id->driver_data;
i2c_set_clientdata(client, m41t80_data);
@@ -801,6 +969,10 @@ static int m41t80_probe(struct i2c_client *client,
}
}
#endif
+#ifdef CONFIG_COMMON_CLK
+ if (m41t80_data->features & M41T80_FEATURE_SQ)
+ m41t80_sqw_register_clk(m41t80_data);
+#endif
return 0;
}
--
2.11.0
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