linux-kernel - Re: [PATCH 09/10] timer-riscv: Fix undefined riscv_time

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Date:   Tue, 19 May 2020 15:51:08 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Palmer Dabbelt <palmer@...belt.com>, tglx@...utronix.de
Cc:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        hulkci@...wei.com
Subject: Re: [PATCH 09/10] timer-riscv: Fix undefined riscv_time_val

On 19/05/2020 14:39, Kefeng Wang wrote:
> 
> On 2020/5/19 4:23, Daniel Lezcano wrote:
>> Hi Kefeng,
>>
>> On 18/05/2020 17:40, Kefeng Wang wrote:
>>> On 2020/5/18 22:09, Daniel Lezcano wrote:
>>>> On 13/05/2020 23:14, Palmer Dabbelt wrote:
>>>>> On Sun, 10 May 2020 19:20:00 PDT (-0700), wangkefeng.wang@...wei.com
>>>>> wrote:
>>>>>> ERROR: modpost: "riscv_time_val" [crypto/tcrypt.ko] undefined!
>>>>>>
>>>>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>>>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>>>>>> ---
>>>>>>    drivers/clocksource/timer-riscv.c | 1 +
>>>>>>    1 file changed, 1 insertion(+)
>>>>>>
>>>>>> diff --git a/drivers/clocksource/timer-riscv.c
>>>>>> b/drivers/clocksource/timer-riscv.c
>>>>>> index c4f15c4068c0..071b8c144027 100644
>>>>>> --- a/drivers/clocksource/timer-riscv.c
>>>>>> +++ b/drivers/clocksource/timer-riscv.c
>>>>>> @@ -19,6 +19,7 @@
>>>>>>
>>>>>>    u64 __iomem *riscv_time_cmp;
>>>>>>    u64 __iomem *riscv_time_val;
>>>>>> +EXPORT_SYMBOL(riscv_time_val);
>>>>>>
>>>>>>    static inline void mmio_set_timer(u64 val)
>>>>>>    {
>>>>> Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
>>>>> Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
>>>>>
>>>>> Adding the clocksource maintainers.  Let me know if you want this
>>>>> through my
>>>>> tree, I'm assuming you want it through your tree.
>>>> How can we end up by an export symbol here ?!
>>> Hi Danile,
>> s/Danile/Daniel/
> Sorry for typing error.
>>
>>> Found this build error when CONFIG_RISCV_M_MODE=y and CONFIG_RISCV_SBI
>>> is not,
>>>
>>> see patch "4f9bbcefa142 riscv: add support for MMIO access to the timer
>>> registers"
>> Thanks for the pointer.
>>
>> The question still remains, how do we end up with this EXPORT_SYMBOL?
>>
>> There is something wrong if the fix is an EXPORT_SYMBOL for a global
>> variable.
> 
> Not very clear, there are some global variable( eg, acpi_disabled,
> memstart_addr in arm64,) is exported by EXPORT_SYMBOL,  do you mean that
> export riscv_time_val is wrong way?

I do not maintain acpi neither arm64.mm.

AFAICT, riscv_time_val is globally declared in
drivers/clocksource/timer-riscv.c

The driver does not use this variable at all. Then there is a readl on
it in the header file arch/riscv/include/asm/timex.h

And finally it is initialized in arch/riscv/kernel/clint.c

Same thing for riscv_time_cmp.

The correct fix is to initialize the variables in the place where they
belong to (drivers/clocksource/timer-riscv.c), create a function to read
their content and export-symbol-gpl the function.


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