* [PATCH] clk:mmp: clk-mix.c fix divide-by-zero
@ 2019-03-29 11:46 nixiaoming
2019-03-29 12:41 ` Mukesh Ojha
2019-03-29 22:48 ` Stephen Boyd
0 siblings, 2 replies; 4+ messages in thread
From: nixiaoming @ 2019-03-29 11:46 UTC (permalink / raw)
To: mturquette, sboyd, nixiaoming, chao.xie; +Cc: linux-clk, linux-kernel
The _get_div function has a branch with a return value of 0
Add a check on the return value of _get_div to avoid divide-by-zero
Signed-off-by: nixiaoming <nixiaoming@huawei.com>
---
drivers/clk/mmp/clk-mix.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/clk/mmp/clk-mix.c b/drivers/clk/mmp/clk-mix.c
index 90814b2..9d152c2 100644
--- a/drivers/clk/mmp/clk-mix.c
+++ b/drivers/clk/mmp/clk-mix.c
@@ -245,6 +245,8 @@ static int mmp_clk_mix_determine_rate(struct clk_hw *hw,
div_val_max = _get_maxdiv(mix);
for (j = 0; j < div_val_max; j++) {
div = _get_div(mix, j);
+ if (!div) /* avoid divide-by-zero */
+ continue;
mix_rate = parent_rate / div;
gap = abs(mix_rate - req->rate);
if (!parent_best || gap < gap_best) {
@@ -341,6 +343,8 @@ static unsigned long mmp_clk_mix_recalc_rate(struct clk_hw *hw,
shift = mix->reg_info.shift_div;
div = _get_div(mix, MMP_CLK_BITS_GET_VAL(mux_div, width, shift));
+ if (!div) /* avoid divide-by-zero */
+ return -EINVAL;
return parent_rate / div;
}
--
1.8.5.6
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] clk:mmp: clk-mix.c fix divide-by-zero
2019-03-29 11:46 [PATCH] clk:mmp: clk-mix.c fix divide-by-zero nixiaoming
@ 2019-03-29 12:41 ` Mukesh Ojha
2019-03-29 22:48 ` Stephen Boyd
1 sibling, 0 replies; 4+ messages in thread
From: Mukesh Ojha @ 2019-03-29 12:41 UTC (permalink / raw)
To: nixiaoming, mturquette, sboyd, chao.xie; +Cc: linux-clk, linux-kernel
On 3/29/2019 5:16 PM, nixiaoming wrote:
> The _get_div function has a branch with a return value of 0
> Add a check on the return value of _get_div to avoid divide-by-zero
>
> Signed-off-by: nixiaoming <nixiaoming@huawei.com>
Fix the below minor comments..
Otherwise things look good..you can take mine
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
after fixing it.
Cheers,
-Mukesh
> ---
> drivers/clk/mmp/clk-mix.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/clk/mmp/clk-mix.c b/drivers/clk/mmp/clk-mix.c
> index 90814b2..9d152c2 100644
> --- a/drivers/clk/mmp/clk-mix.c
> +++ b/drivers/clk/mmp/clk-mix.c
> @@ -245,6 +245,8 @@ static int mmp_clk_mix_determine_rate(struct clk_hw *hw,
> div_val_max = _get_maxdiv(mix);
> for (j = 0; j < div_val_max; j++) {
> div = _get_div(mix, j);
> + if (!div) /* avoid divide-by-zero */
Please move this comment at the top of the check.
> + continue;
> mix_rate = parent_rate / div;
> gap = abs(mix_rate - req->rate);
> if (!parent_best || gap < gap_best) {
> @@ -341,6 +343,8 @@ static unsigned long mmp_clk_mix_recalc_rate(struct clk_hw *hw,
> shift = mix->reg_info.shift_div;
>
> div = _get_div(mix, MMP_CLK_BITS_GET_VAL(mux_div, width, shift));
> + if (!div) /* avoid divide-by-zero */
ditto
> + return -EINVAL;
>
> return parent_rate / div;
> }
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] clk:mmp: clk-mix.c fix divide-by-zero
2019-03-29 11:46 [PATCH] clk:mmp: clk-mix.c fix divide-by-zero nixiaoming
2019-03-29 12:41 ` Mukesh Ojha
@ 2019-03-29 22:48 ` Stephen Boyd
2019-03-30 2:20 ` Nixiaoming
1 sibling, 1 reply; 4+ messages in thread
From: Stephen Boyd @ 2019-03-29 22:48 UTC (permalink / raw)
To: chao.xie, mturquette, nixiaoming; +Cc: linux-clk, linux-kernel
Quoting nixiaoming (2019-03-29 04:46:00)
> The _get_div function has a branch with a return value of 0
> Add a check on the return value of _get_div to avoid divide-by-zero
>
> Signed-off-by: nixiaoming <nixiaoming@huawei.com>
Similar questions apply here as they do on the generic divider patch you
sent.
> ---
> drivers/clk/mmp/clk-mix.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/clk/mmp/clk-mix.c b/drivers/clk/mmp/clk-mix.c
> index 90814b2..9d152c2 100644
> --- a/drivers/clk/mmp/clk-mix.c
> +++ b/drivers/clk/mmp/clk-mix.c
> @@ -245,6 +245,8 @@ static int mmp_clk_mix_determine_rate(struct clk_hw *hw,
> div_val_max = _get_maxdiv(mix);
> for (j = 0; j < div_val_max; j++) {
> div = _get_div(mix, j);
> + if (!div) /* avoid divide-by-zero */
Why can't we return 1 for the divider value here?
> + continue;
> mix_rate = parent_rate / div;
> gap = abs(mix_rate - req->rate);
> if (!parent_best || gap < gap_best) {
> @@ -341,6 +343,8 @@ static unsigned long mmp_clk_mix_recalc_rate(struct clk_hw *hw,
> shift = mix->reg_info.shift_div;
>
> div = _get_div(mix, MMP_CLK_BITS_GET_VAL(mux_div, width, shift));
> + if (!div) /* avoid divide-by-zero */
Same question.
> + return -EINVAL;
>
> return parent_rate / div;
> }
^ permalink raw reply [flat|nested] 4+ messages in thread
* RE: [PATCH] clk:mmp: clk-mix.c fix divide-by-zero
2019-03-29 22:48 ` Stephen Boyd
@ 2019-03-30 2:20 ` Nixiaoming
0 siblings, 0 replies; 4+ messages in thread
From: Nixiaoming @ 2019-03-30 2:20 UTC (permalink / raw)
To: Stephen Boyd, chao.xie, mturquette; +Cc: linux-clk, linux-kernel
On 3/30/2019 6:48 AM Stephen Boyd wrote:
>Quoting nixiaoming (2019-03-29 04:46:00)
>> The _get_div function has a branch with a return value of 0
>> Add a check on the return value of _get_div to avoid divide-by-zero
>>
>> Signed-off-by: nixiaoming <nixiaoming@huawei.com>
>
>Similar questions apply here as they do on the generic divider patch you
>sent.
>
_get_div() in both files is a different function, with a divide-by-zero problem
I will organize it into a patch set later.
>> ---
>> drivers/clk/mmp/clk-mix.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/clk/mmp/clk-mix.c b/drivers/clk/mmp/clk-mix.c
>> index 90814b2..9d152c2 100644
>> --- a/drivers/clk/mmp/clk-mix.c
>> +++ b/drivers/clk/mmp/clk-mix.c
>> @@ -245,6 +245,8 @@ static int mmp_clk_mix_determine_rate(struct clk_hw *hw,
>> div_val_max = _get_maxdiv(mix);
>> for (j = 0; j < div_val_max; j++) {
>> div = _get_div(mix, j);
>> + if (!div) /* avoid divide-by-zero */
>
>Why can't we return 1 for the divider value here?
I personally understand that an exception or skip should be thrown after dividing by 0.
Directly modified to other values, I am not sure whether it affects the logic
My logical understanding of this code is not clear enough, I still need your guidance.
>
>> + continue;
>> mix_rate = parent_rate / div;
>> gap = abs(mix_rate - req->rate);
>> if (!parent_best || gap < gap_best) {
>> @@ -341,6 +343,8 @@ static unsigned long mmp_clk_mix_recalc_rate(struct clk_hw *hw,
>> shift = mix->reg_info.shift_div;
>>
>> div = _get_div(mix, MMP_CLK_BITS_GET_VAL(mux_div, width, shift));
>> + if (!div) /* avoid divide-by-zero */
>
>Same question.
I personally understand that an exception or skip should be thrown after dividing by 0.
Directly modified to other values, I am not sure whether it affects the logic
My logical understanding of this code is not clear enough, I still need your guidance.
>
>> + return -EINVAL;
>>
>> return parent_rate / div;
>> }
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-03-29 11:46 [PATCH] clk:mmp: clk-mix.c fix divide-by-zero nixiaoming
2019-03-29 12:41 ` Mukesh Ojha
2019-03-29 22:48 ` Stephen Boyd
2019-03-30 2:20 ` Nixiaoming
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