Commit 13bb1d78 authored Nov 02, 2017 by Troy Kisky Committed by Alexandre Belloni Nov 08, 2017

rtc: m41t80: avoid i2c read in m41t80_sqw_is_prepared



This is a little more efficient and avoids the warning

 WARNING: possible circular locking dependency detected
 4.14.0-rc7-00010 #16 Not tainted
 ------------------------------------------------------
 kworker/2:1/70 is trying to acquire lock:
  (prepare_lock){+.+.}, at: [<c049300c>] clk_prepare_lock+0x80/0xf4

 but task is already holding lock:
  (i2c_register_adapter){+.+.}, at: [<c0690b04>]
		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_is_prepared+0x18/0x28

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

parent 2cb90ed3

drivers/rtc/rtc-m41t80.c

+6 −9

Original line number	Diff line number	Diff line
		@@ -155,6 +155,7 @@ struct m41t80_data {
		#ifdef CONFIG_COMMON_CLK
		struct clk_hw sqw;
		unsigned long freq;
		unsigned int sqwe;
		#endif
		};

		@@ -527,7 +528,10 @@ static int m41t80_sqw_control(struct clk_hw *hw, bool enable)
		else
		ret &= ~M41T80_ALMON_SQWE;

		return i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);
		ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);
		if (!ret)
		m41t80->sqwe = enable;
		return ret;
		}

		static int m41t80_sqw_prepare(struct clk_hw *hw)
		@@ -542,14 +546,7 @@ static void m41t80_sqw_unprepare(struct clk_hw *hw)

		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);
		return sqw_to_m41t80_data(hw)->sqwe;
		}

		static const struct clk_ops m41t80_sqw_ops = {

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