Re: [PATCH v7 00/22] RISC-V Kendryte K210 support improvements

[Damien Le Moal <Damien.LeMoal@xxxxxxx>]

On 2020/12/10 22:23, Geert Uytterhoeven wrote:
> Hi Damien,
> 
> On Thu, Dec 10, 2020 at 1:36 PM Damien Le Moal <Damien.LeMoal@xxxxxxx> wrote:
>> On Thu, 2020-12-10 at 11:04 +0100, Geert Uytterhoeven wrote:
>>> On Thu, Dec 10, 2020 at 4:41 AM Damien Le Moal <damien.lemoal@xxxxxxx> wrote:
>>>> Changes from v6:
>>>> * Annotate struct platform_driver variables with __refdata to avoid
>>>>   section mismatch compilation errors
>>>
>>> Blindly following the advice from kernel test robot <lkp@xxxxxxxxx> is
>>> not always a good idea:
>>>
>>>     The variable k210_rst_driver references
>>>     the function __init set_reset_devices()
>>>     If the reference is valid then annotate the
>>>     variable with or __refdata (see linux/init.h) or name the variable:
>>>
>>> If your driver's probe function is annotated with __init, you cannot
>>> have a pointer to it in the driver structure, as any binding done after
>>> the freeing of initmem will cause a crash.  Adding the __refdata merely
>>> suppresses the warning, and won't avoid the crash.
>>
>> Hmm... I must be misunderstanding something here. free_initmem() is called from
>> kernel_init() right before starting the user init process. That is late enough
>> that all drivers are already probed and initialized. At least that is what I
>> thought, especially considering that none of the k210 drivers can be modules
>> and are all builtin. What am I missing here ?
> 
> For these specific cases, binding is indeed unlikely to happen after
> free_initmem(). In the generic case that is not true.
> However, you can still trigger it manually by unbinding and rebinding
> the device manually through sysfs.

Got it. Sending a v8 with the correction.

Thanks !

> 
>> So I think I will go with option 2. It is simpler and safer. We can always
>> revisit and optimize later. I would prefer this series to land first :)
> 
> Right. Correctness first, performance later.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 


-- 
Damien Le Moal
Western Digital Research