linux-kernel - [PATCH AUTOSEL 4.18 019/131] clk: scmi: Fix the rounding of clock rate

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Date:   Sun, 2 Sep 2018 13:03:22 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Amit Daniel Kachhap <amit.kachhap@....com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.18 019/131] clk: scmi: Fix the rounding of clock
 rate

From: Amit Daniel Kachhap <amit.kachhap@....com>

[ Upstream commit 7a8655e19bdb3be43f6a3b4768c9b0928a2585fc ]

This fix rounds the clock rate properly by using quotient and not
remainder in the calculation. This issue was found while testing HDMI
in the Juno platform.

Fixes: 6d6a1d82eaef7 ("clk: add support for clocks provided by SCMI")
Acked-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
Signed-off-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/clk/clk-scmi.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index bb2a6f2f5516..a985bf5e1ac6 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -38,7 +38,6 @@ static unsigned long scmi_clk_recalc_rate(struct clk_hw *hw,
 static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long *parent_rate)
 {
-	int step;
 	u64 fmin, fmax, ftmp;
 	struct scmi_clk *clk = to_scmi_clk(hw);
 
@@ -60,9 +59,9 @@ static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
 
 	ftmp = rate - fmin;
 	ftmp += clk->info->range.step_size - 1; /* to round up */
-	step = do_div(ftmp, clk->info->range.step_size);
+	do_div(ftmp, clk->info->range.step_size);
 
-	return step * clk->info->range.step_size + fmin;
+	return ftmp * clk->info->range.step_size + fmin;
 }
 
 static int scmi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
-- 
2.17.1