linux-kernel - [PATCH 4.14 11/14] rtc: m41t80: fix m41t80_sqw_round

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Date:   Thu,  4 Jan 2018 13:09:28 +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 11/14] rtc: m41t80: fix m41t80_sqw_round_rate return value

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

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

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

commit c8384bb04261b9d32fe7402a6068ddaf38913b23 upstream.

Previously it was returning the best of
32768, 8192, 1024, 64, 2, 0

Now, best of
32768, 8192, 4096, 2048, 1024, 512, 256, 128,
64, 32, 16, 8, 4, 2, 1, 0

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 |   19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -468,18 +468,13 @@ static unsigned long m41t80_sqw_recalc_r
 static long m41t80_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
 				  unsigned long *prate)
 {
-	int i, freq = M41T80_SQW_MAX_FREQ;
-
-	if (freq <= rate)
-		return freq;
-
-	for (i = 2; i <= ilog2(M41T80_SQW_MAX_FREQ); i++) {
-		freq /= 1 << i;
-		if (freq <= rate)
-			return freq;
-	}
-
-	return 0;
+	if (rate >= M41T80_SQW_MAX_FREQ)
+		return M41T80_SQW_MAX_FREQ;
+	if (rate >= M41T80_SQW_MAX_FREQ / 4)
+		return M41T80_SQW_MAX_FREQ / 4;
+	if (!rate)
+		return 0;
+	return 1 << ilog2(rate);
 }
 
 static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate,