linux-kernel - [PATCH 4.14 14/14] rtc: m41t80: remove unneeded checks from m41t80_sqw_set

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Date:   Thu,  4 Jan 2018 13:09:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Troy Kisky <troy.kisky@...ndarydevices.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Christoph Fritz <chf.fritz@...glemail.com>
Subject: [PATCH 4.14 14/14] rtc: m41t80: remove unneeded checks from m41t80_sqw_set_rate

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Troy Kisky <troy.kisky@...ndarydevices.com>

commit 05a03bf260e0480bfc0db91b1fdbc2115e3f193b upstream.

m41t80_sqw_set_rate will be called with the result from
m41t80_sqw_round_rate, so might as well make
m41t80_sqw_set_rate(n) same as
m41t80_sqw_set_rate(m41t80_sqw_round_rate(n))

As Russell King wrote[1],
"clk_round_rate() is supposed to tell you what you end up with if you
ask clk_set_rate() to set the exact same value you passed in - but
clk_round_rate() won't modify the hardware."

[1]
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-January/080175.html

Signed-off-by: Troy Kisky <troy.kisky@...ndarydevices.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc: Christoph Fritz <chf.fritz@...glemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/rtc/rtc-m41t80.c |   17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -490,17 +490,12 @@ static int m41t80_sqw_set_rate(struct cl
 		M41T80_REG_WDAY : M41T80_REG_SQW;
 	int reg, ret, val = 0;
 
-	if (rate) {
-		if (!is_power_of_2(rate))
-			return -EINVAL;
-		val = ilog2(rate);
-		if (val == ilog2(M41T80_SQW_MAX_FREQ))
-			val = 1;
-		else if (val < (ilog2(M41T80_SQW_MAX_FREQ) - 1))
-			val = ilog2(M41T80_SQW_MAX_FREQ) - val;
-		else
-			return -EINVAL;
-	}
+	if (rate >= M41T80_SQW_MAX_FREQ)
+		val = 1;
+	else if (rate >= M41T80_SQW_MAX_FREQ / 4)
+		val = 2;
+	else if (rate)
+		val = 15 - ilog2(rate);
 
 	reg = i2c_smbus_read_byte_data(client, reg_sqw);
 	if (reg < 0)