Re: [PATCH 1/1] x86/amd_nb: unexport amd_cache_northbridges()

["Chatradhi, Naveen Krishna" <nchatrad@amd.com>]

Hi Boris,

On 3/15/2022 10:58 PM, Borislav Petkov wrote:
> [CAUTION: External Email]
>
> On Mon, Feb 28, 2022 at 09:41:54PM +0530, Naveen Krishna Chatradhi wrote:
>> From: Muralidhara M K <muralimk@amd.com>
>>
>> amd_cache_northbridges() is called from init_amd_nbs(), during
>> fs_initcall() and need not be called explicitly. Kernel components
>> can directly call amd_nb_num() to get the initialized number of
>> north bridges.
>>
>> unexport amd_cache_northbridges(), update dependent modules to
>> call amd_nb_num() instead. While at it, simplify the while checks
>> in amd_cache_northbridges().
Apologies for the late reply.
> What I am missing in this commit message is why is it ok to do that?
>
> AFAIR, previously, amd_cache_northbridges() wasn't an initcall so the
> module or builtin - which came first - was forcing the NB caching
> through the explicit call to amd_cache_northbridges().
>
> fs_inicall() does that now unconditionally so the question is, why can
> the module init functions assume that the northbridges have been cached
> already and can simply get the NB number?

Modules that are using this API comes after the fs_initcall() is called.

This patch is prepared based on a previous discussion

https://lore.kernel.org/lkml/bcf5e86c-d3f1-0dab-2bed-505b1eb95f17@amd.com/

quoting from the thread

 > I'm going to venture a pretty sure guess that the initcall runs first
 > and that amd_cache_northbridges() call in amd64_edac_init() is probably

 > not even needed anymore...

and i've confirmed the call flow.

>
> Thx.
>
> --
> Regards/Gruss,
>      Boris.
>
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Regards,

Naveenk