This is a note to let you know that I've just added the patch titled
rtc: m41t80: avoid i2c read in m41t80_sqw_is_prepared
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rtc-m41t80-avoid-i2c-read-in-m41t80_sqw_is_prepared.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 13bb1d78f2e372ec0d9b30489ac63768240140fc Mon Sep 17 00:00:00 2001
From: Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 2 Nov 2017 18:58:15 -0700
Subject: rtc: m41t80: avoid i2c read in m41t80_sqw_is_prepared
From: Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Fritz <chf.fritz@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/rtc/rtc-m41t80.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
--- 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
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
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 = {
Patches currently in stable-queue which might be from troy.kisky@xxxxxxxxxxxxxxxxxxx are
queue-4.14/rtc-m41t80-m41t80_sqw_set_rate-should-return-0-on-success.patch
queue-4.14/rtc-m41t80-avoid-i2c-read-in-m41t80_sqw_is_prepared.patch
queue-4.14/rtc-m41t80-avoid-i2c-read-in-m41t80_sqw_recalc_rate.patch
queue-4.14/rtc-m41t80-remove-unneeded-checks-from-m41t80_sqw_set_rate.patch
queue-4.14/rtc-m41t80-fix-m41t80_sqw_round_rate-return-value.patch