[PATCH] clk: sunxi-ng: fix recalc_rate formula of NKMP clocks

[PATCH] clk: sunxi-ng: fix recalc_rate formula of NKMP clocks

[Icenowy Zheng]

In commit e66f81bbd746 ("clk: sunxi-ng: Implement factors offsets"), the
final formula of NKMP clocks' recalc_rate is refactored; however, the
refactored formula broke the calculation due to some C language operand
priority problem -- the priority of operand >> is lower than * and /,
makes the formula being parsed as "(parent_rate * n * k) >> (p / m)", but
it should be "(parent_rate * n * k >> p) / m".

Add the pair of parentheses to fix up this issue. This pair of
parentheses used to exist in the old formula.

Fixes: commit e66f81bbd746 ("clk: sunxi-ng: Implement factors offsets")
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
---
Please patch the latest git tree master too, as this buggy commit is
introduced in 4.11-rc (for sun5i ccu support).

 drivers/clk/sunxi-ng/ccu_nkmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/sunxi-ng/ccu_nkmp.c b/drivers/clk/sunxi-ng/ccu_nkmp.c
index a2b40a000157..488055ed944f 100644
--- a/drivers/clk/sunxi-ng/ccu_nkmp.c
+++ b/drivers/clk/sunxi-ng/ccu_nkmp.c
@@ -107,7 +107,7 @@ static unsigned long ccu_nkmp_recalc_rate(struct clk_hw *hw,
 	p = reg >> nkmp->p.shift;
 	p &= (1 << nkmp->p.width) - 1;
 
-	return parent_rate * n * k >> p / m;
+	return (parent_rate * n * k >> p) / m;
 }
 
 static long ccu_nkmp_round_rate(struct clk_hw *hw, unsigned long rate,
-- 
2.12.0

[PATCH] clk: sunxi-ng: fix recalc_rate formula of NKMP clocks

[Maxime Ripard]

On Sat, Mar 18, 2017 at 04:19:43AM +0800, Icenowy Zheng wrote:
> In commit e66f81bbd746 ("clk: sunxi-ng: Implement factors offsets"), the
> final formula of NKMP clocks' recalc_rate is refactored; however, the
> refactored formula broke the calculation due to some C language operand
> priority problem -- the priority of operand >> is lower than * and /,
> makes the formula being parsed as "(parent_rate * n * k) >> (p / m)", but
> it should be "(parent_rate * n * k >> p) / m".
> 
> Add the pair of parentheses to fix up this issue. This pair of
> parentheses used to exist in the old formula.
> 
> Fixes: commit e66f81bbd746 ("clk: sunxi-ng: Implement factors offsets")

You shouldn't have commit here.

> Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>

Fixed it, and applied, thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 801 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20170320/5741ef4a/attachment.sig>