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SubjectRe: commit 5146e0b05963 is causing a kernel crash on SoCFPGA
From
2016-02-09 19:11 GMT+09:00 Dinh Nguyen <dinguyen@kernel.org>:
> Hi Masahiro,
>
> On 02/08/2016 10:00 PM, Masahiro Yamada wrote:
>> Hi Dinh,
>>
>> Thanks for your report.
>>
>>
>> 2016-02-09 11:35 GMT+09:00 Dinh Nguyen <dinguyen@kernel.org>:
>>> Hi Stephen,
>>>
>>> It appears that commit 5146e0b05966 "clk: simplify __clk_init_parent()"
>>> that is currently in linux-next is causing the following kernel crash on
>>> SoCFGPA[1].
>>>
>>> I have bisected to this commit and doing a revert of the commit fixes
>>> the issue.
>>
>>
>> Could you check if the following simple patch fixes your problem?
>>
>>
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -1662,7 +1662,7 @@ static struct clk_core *__clk_init_parent(struct
>> clk_core *core)
>> {
>> u8 index = 0;
>>
>> - if (core->ops->get_parent)
>> + if (core->num_parents > 1 && core->ops->get_parent)
>> index = core->ops->get_parent(core->hw);
>>
>> return clk_core_get_parent_by_index(core, index);
>>
>>
>
> Yes, the above patch fixes the problem and the SoCFPGA board is able to
> boot.

Thanks for your testing!

I've sent a patch with your Reported-by.


>>
>>
>> Let me ask one more question.
>>
>> Do SoCFPGA clocks define .get_parent callback even if num_parents <= 1 ?
>>
>>
>> I just skimmed over driver/clk/socfpga/clk-gate.c
>> and found it defines .get_parent().
>>
>> I think a gating clock is usually single-parent (so not need to have
>> .get_parent),
>> but I am not sure if this is the case.
>>
>
> Yes, .get_parent call back is define when num_parents = 1. If you take a
> look at socfpga.dtsi, the main_pll of type "altr,socfpga-pll-clk" only
> has 1 parent, osc1. But the periph_pll and sdram_pll, also of type
> "altr,socfpga-pll-clk" has > 1 parents.


OK. Then, I understood the cause of the problem.



--
Best Regards
Masahiro Yamada

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