RE: [EXTERNAL] Re: [PATCH] misc: Kconfig: add a new dependency for MARVELL_CN10K_DPI

[Vamsi Krishna Attunuru]

>-----Original Message-----
>From: Arnd Bergmann <arnd@xxxxxxxx>
>Sent: Tuesday, July 16, 2024 7:21 PM
>To: Nathan Chancellor <nathan@xxxxxxxxxx>; Vamsi Krishna Attunuru
><vattunuru@xxxxxxxxxxx>
>Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; linux-
>kernel@xxxxxxxxxxxxxxx
>Subject: [EXTERNAL] Re: [PATCH] misc: Kconfig: add a new dependency for
>MARVELL_CN10K_DPI
>
>On Tue, Jul 16, 2024, at 15: 26, Nathan Chancellor wrote: > On Thu, Jul 11, 2024
>at 05: 01: 15AM -0700, Vamsi Attunuru wrote: >> > > After this change,
>ARCH=arm allmodconfig fails with: > > drivers/misc/mrvl_cn10k_dpi. c: In
>
>On Tue, Jul 16, 2024, at 15:26, Nathan Chancellor wrote:
>> On Thu, Jul 11, 2024 at 05:01:15AM -0700, Vamsi Attunuru wrote:
>>>
>>
>> After this change, ARCH=arm allmodconfig fails with:
>>
>>   drivers/misc/mrvl_cn10k_dpi.c: In function 'dpi_reg_write':
>>   drivers/misc/mrvl_cn10k_dpi.c:190:9: error: implicit declaration of
>> function 'writeq'; did you mean 'writeb'?
>> [-Wimplicit-function-declaration]
>>     190 |         writeq(val, dpi->reg_base + offset);
>>         |         ^~~~~~
>>         |         writeb
>>   drivers/misc/mrvl_cn10k_dpi.c: In function 'dpi_reg_read':
>>   drivers/misc/mrvl_cn10k_dpi.c:195:16: error: implicit declaration of
>> function 'readq'; did you mean 'readb'?
>> [-Wimplicit-function-declaration]
>>     195 |         return readq(dpi->reg_base + offset);
>>         |                ^~~~~
>>         |                readb
>>
>> Including one of the io-64-nonatomic headers would resolve this but I
>> am not sure which one would be appropriate (or perhaps the dependency
>> should be tightened to requiring 64BIT, as some other drivers have
>> done).
>
>Right, a dependency on 64BIT makes sense here. The alternative is to include
>linux/io-64-nonatomic-hi-lo.h or linux/io-64-nonatomic-lo-hi.h in order to
>have a replacement readq/writeq implementation that works on 32-bit
>architectures. However, doing this requires understanding whether what the
>side-effects of accessing the 64-bit registers are and whether they require
>writing the upper or lower half of the register last.
>

Yes Arnd, I am checking the functionality using lo-hi calls that you suggested.
If it has any implications, I will fix it with the 64BIT dependency.

Thanks, Nathan, for reaching out. Could you please advise on the branch where
I should implement the fix.



>     Arnd