rtc: m41t80: avoid i2c read in m41t80_sqw_is_prepared

commit 13bb1d78f2e372ec0d9b30489ac63768240140fc upstream.

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>
Cc: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index f44dcf628c87b7a9e619e444e46ee0fe79881bc8..96a606d5f6e69b9bb9d686fb3413449fb545e71d 100644 (file)
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -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 = {