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SubjectRe: [PATCH 1/1] clk-divider: fix is_power_of_two()
On 16/01/13 00:56, Mike Turquette wrote:
> Quoting Joe Perches (2013-01-15 10:31:05)
>> On Tue, 2013-01-15 at 10:28 +0000, James Hogan wrote:
>>> The macro is_power_of_two() in clk-divider.c was defined as !(i & ~i)
>>> which is always true. Correct it to !(i & (i - 1)).
>> []
>>> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
>> []
>>> @@ -29,8 +29,8 @@
>> []
>>> -#define div_mask(d) ((1 << (d->width)) - 1)
>>> -#define is_power_of_two(i) !(i & ~i)
>>> +#define div_mask(d) ((1 << ((d)->width)) - 1)
>>> +#define is_power_of_two(i) (!((i) & ((i) - 1)))
>>
>> Use is_power_of_2 in log2.h instead?
>
> Both are fine suggestions. How about I apply the below patch?

Looks good to me, thanks for taking care of the log.h change.

Cheers
James

> From 54c6c9e5f61693effbe6e4fb28ef9f2f9b3d7a23 Mon Sep 17 00:00:00 2001
> From: James Hogan <james.hogan@imgtec.com>
> Date: Tue, 15 Jan 2013 10:28:05 +0000
> Subject: [PATCH] clk-divider: fix macros
>
> The macro is_power_of_two() in clk-divider.c was defined as !(i & ~i)
> which is always true. Instead use is_power_of_2() from log2.h.
>
> Also add brackets around the macro arguments in div_mask to avoid any
> future operator precedence problems.
>
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Cc: Joe Perches <joe@perches.com>
> Signed-off-by: Mike Turquette <mturquette@linaro.org>
> [mturquette@linaro.org: use log2.h per Joe Perches; update changelog]
> ---
> drivers/clk/clk-divider.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index a9204c6..68b4021 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -16,6 +16,7 @@
> #include <linux/io.h>
> #include <linux/err.h>
> #include <linux/string.h>
> +#include <linux/log2.h>
>
> /*
> * DOC: basic adjustable divider clock that cannot gate
> @@ -29,8 +30,7 @@
>
> #define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
>
> -#define div_mask(d) ((1 << (d->width)) - 1)
> -#define is_power_of_two(i) !(i & ~i)
> +#define div_mask(d) ((1 << ((d)->width)) - 1)
>
> static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
> {
> @@ -137,7 +137,7 @@ static bool _is_valid_table_div(const struct clk_div_table *table,
> static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
> {
> if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
> - return is_power_of_two(div);
> + return is_power_of_2(div);
> if (divider->table)
> return _is_valid_table_div(divider->table, div);
> return true;
>



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