Patch "rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

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;a=summary

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