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rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate

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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: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Troy Kisky 2017-11-02 18:58:14 -07:00 committed by Alexandre Belloni
parent c8384bb042
commit 2cb90ed3de
1 changed files with 17 additions and 11 deletions
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28
drivers/rtc/rtc-m41t80.c
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@ -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);