Commit 2cb90ed3 authored by Troy Kisky's avatar Troy Kisky Committed by Alexandre Belloni
Browse files

rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate 



This is a little more efficient, and avoids the warning

 WARNING: possible circular locking dependency detected
 4.14.0-rc7-00007 #14 Not tainted
 ------------------------------------------------------
 alsactl/330 is trying to acquire lock:
 (prepare_lock){+.+.}, at: [<c049300c>] clk_prepare_lock+0x80/0xf4

 but task is already holding lock:
 (i2c_register_adapter){+.+.}, at: [<c0690ae0>]
		i2c_adapter_lock_bus+0x14/0x18

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #1 (i2c_register_adapter){+.+.}:
        rt_mutex_lock+0x44/0x5c
        i2c_adapter_lock_bus+0x14/0x18
        i2c_transfer+0xa8/0xbc
        i2c_smbus_xfer+0x20c/0x5d8
        i2c_smbus_read_byte_data+0x38/0x48
        m41t80_sqw_recalc_rate+0x24/0x58

Signed-off-by: default avatarTroy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent c8384bb0

drivers/rtc/rtc-m41t80.c

+17 −11
Original line number Diff line number Diff line
@@ -154,6 +154,7 @@ struct m41t80_data { 
	struct rtc_device *rtc;

#ifdef CONFIG_COMMON_CLK

	struct clk_hw sqw;

	unsigned long freq;

#endif

};
@@ -443,26 +444,28 @@ static SIMPLE_DEV_PM_OPS(m41t80_pm, m41t80_suspend, m41t80_resume); 
#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)

static unsigned long m41t80_decode_freq(int setting)

{

	return (setting == 0) ? 0 : (setting == 1) ? M41T80_SQW_MAX_FREQ :

		M41T80_SQW_MAX_FREQ >> setting;

}



static unsigned long m41t80_get_freq(struct m41t80_data *m41t80)

{

	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;

	return m41t80_decode_freq(ret >> 4);

}



	ret >>= 4;

	if (ret == 0)

		val = 0;

	else if (ret > 1)

		val = val / (1 << ret);



	return val;

static unsigned long m41t80_sqw_recalc_rate(struct clk_hw *hw,

					    unsigned long parent_rate)

{

	return sqw_to_m41t80_data(hw)->freq;

}



static long m41t80_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -505,6 +508,8 @@ static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate, 
	reg = (reg & 0x0f) | (val << 4);



	ret = i2c_smbus_write_byte_data(client, reg_sqw, reg);

	if (!ret)

		m41t80->freq = m41t80_decode_freq(val);

	return ret;

}
@@ -579,6 +584,7 @@ static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80) 
	init.parent_names = NULL;

	init.num_parents = 0;

	m41t80->sqw.init = &init;

	m41t80->freq = m41t80_get_freq(m41t80);



	/* optional override of the clockname */

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

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