This is a note to let you know that I've just added the patch titled

rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: rtc-m41t80-avoid-i2c-read-in-m41t80_sqw_recalc_rate.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@vger.kernel.org know about it.

From 2cb90ed3de1e279dbaf23df141f54eb9fb1861e6 Mon Sep 17 00:00:00 2001

From: Troy Kisky troy.kisky@boundarydevices.com Date: Thu, 2 Nov 2017 18:58:14 -0700 Subject: rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate

From: Troy Kisky troy.kisky@boundarydevices.com

commit 2cb90ed3de1e279dbaf23df141f54eb9fb1861e6 upstream.

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

--- drivers/rtc/rtc-m41t80.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-)

--- a/drivers/rtc/rtc-m41t80.c +++ b/drivers/rtc/rtc-m41t80.c @@ -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, m41t #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 cl 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_c 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);

Patches currently in stable-queue which might be from troy.kisky@boundarydevices.com 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