linux-kernel - [PATCH] clk: sunxi: Fix M factor computation for APB1

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Date:   Fri,  4 Nov 2016 00:53:56 +0100
From:   Stéphan Rafin <stephan@...iotek.com>
To:     emilio@...pez.com.ar
Cc:     mturquette@...libre.com, sboyd@...eaurora.org,
        maxime.ripard@...e-electrons.com, wens@...e.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...glegroups.com,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stéphan Rafin <stephan@...iotek.com>
Subject: [PATCH] clk: sunxi: Fix M factor computation for APB1

commit cfa636886033 ("clk: sunxi: factors: Consolidate get_factors
parameters into a struct") introduced a regression for m factor
computation in sun4i_get_apb1_factors function.

The old code reassigned the "parent_rate" parameter to the targeted
divisor value and was buggy for the returned frequency but not for the
computed factors. Now, returned frequency is good but m factor is
incorrectly computed (its max value 31 is always set resulting in a
significantly slower frequency than the requested one...)

This patch simply restores the original proper computation for m while
keeping the good changes for returned rate.

Signed-off-by: Stéphan Rafin <stephan@...iotek.com>
---
 drivers/clk/sunxi/clk-sunxi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/sunxi/clk-sunxi.c b/drivers/clk/sunxi/clk-sunxi.c
index 838b22a..f2c9274 100644
--- a/drivers/clk/sunxi/clk-sunxi.c
+++ b/drivers/clk/sunxi/clk-sunxi.c
@@ -373,7 +373,7 @@ static void sun4i_get_apb1_factors(struct factors_request *req)
 	else
 		calcp = 3;

-	calcm = (req->parent_rate >> calcp) - 1;
+	calcm = (div >> calcp) - 1;

 	req->rate = (req->parent_rate >> calcp) / (calcm + 1);
 	req->m = calcm;
-- 
2.6.6