Re: [PATCH v3 01/11] stm class: Introduce an abstraction for System Trace Module devices

[Chunyan Zhang]

On Thu, Jul 30, 2015 at 2:37 PM, Alexander Shishkin
<alexander.shishkin@xxxxxxxxxxxxxxx> wrote:
> Chunyan Zhang <zhang.lyra@xxxxxxxxx> writes:
>
>> Sure, I mean, the root reason of this problem is here ( i.e.
>> "stm_core_up" was zero then):
>>      if (!stm_core_up)
>>          return -EPROBE_DEFER;
>>
>> Why it was zero?
>> Because the function (i.e. stm_core_init() ) in which "stm_core_up"
>> would be added one hasn't been executed at this moment. It would be
>> executed on module_init stage for you this version of patch.
>
> Again, this is the indented behavior.
>
>> The reason of this warning is:
>> After stm_probe() failed, clk_core_disable() would be called from
>> amba_put_disable_pclk(), then WARN_ON() happened:
>>          if (WARN_ON(core->enable_count == 0))
>>                  return;
>>
>> I'm guessing the reason why "core->enable_count" was 0 at this moment is:
>> I don't know who created a thread to process the
>> amba_pm_runtime_suspend(), in which clk_core_disable() was already
>> called, "core->enable_count" was, of course, cleared to zero then.
>> And this thread run before amba_put_disable_pclk(pcdev) which is just
>> the one called from amba_probe() after
>> "->probe"(i.e. stm_probe in this case) returning a non-zero value.
>
> No, this is guesswork. In amba_probe(), clocks are enabled for the
> drv->probe() and then disabled afterwards and that's where the refcount
> ends up unbalanced, the probe is the culprit.
>
> I can debug your driver for you but you'll at least need to put the code
> up somewhere so I can see it.

The code has already been submitted like I said in the earlier emails,
you may refer [1].

Thanks,
Chunyan

[1] https://lkml.org/lkml/2015/2/4/729

>
> Regards,
> --
> Alex
>
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