linux-kernel - Re: [PATCH v8 07/13] drivers: base cacheinfo: Add support for ACPI based firmware tables

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Message-ID: <14062628-d6bb-2e46-fd7c-edce814b5d22@arm.com>
Date:   Fri, 27 Apr 2018 13:49:51 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jeremy Linton <jeremy.linton@....com>, linux-acpi@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        linux-arm-kernel@...ts.infradead.org, Lorenzo.Pieralisi@....com,
        hanjun.guo@...aro.org, rjw@...ysocki.net, Will.Deacon@....com,
        Catalin.Marinas@....com, gregkh@...uxfoundation.org,
        Mark.Rutland@....com, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, wangxiongfeng2@...wei.com,
        vkilari@...eaurora.org, ahs3@...hat.com, Dietmar.Eggemann@....com,
        Morten.Rasmussen@....com, palmer@...ive.com, lenb@...nel.org,
        john.garry@...wei.com, austinwc@...eaurora.org,
        tnowicki@...iumnetworks.com, jhugo@....qualcomm.com,
        timur@....qualcomm.com, ard.biesheuvel@...aro.org
Subject: Re: [PATCH v8 07/13] drivers: base cacheinfo: Add support for ACPI
 based firmware tables



On 26/04/18 19:57, Jeremy Linton wrote:
> Hi,
> 
> On 04/26/2018 06:05 AM, Sudeep Holla wrote:
>>
>>
>> On 26/04/18 00:31, Jeremy Linton wrote:
>>> Call ACPI cache parsing routines from base cacheinfo code if ACPI
>>> is enable. Also stub out cache_setup_acpi() so that individual
>>> architectures can enable ACPI topology parsing.
>>>
>>
>> [...]
>>
>>> +#ifndef CONFIG_ACPI
>>> +static inline int acpi_find_last_cache_level(unsigned int cpu)
>>> +{
>>> +    /* ACPI kernels should be built with PPTT support */
>>
>> This sounds incorrect for x86. But I understand why you have it there.
>> Does it makes sense to change above to .. ?
>>
>> #if !defined(CONFIG_ACPI) || (defined(CONFIG_ACPI) &&
>> !(CONFIG_ACPI_PPTT))
>>
> I'm not sure what that buys us, if anything you want more non-users of
> the function to be falling through to the function prototype rather than
> the static inline. The only place any of this matters (as long as the
> compiler/linker is tossing the static inline) is arm64 because its the
> only arch making a call to acpi_find_last_cache_level(). ACPI_PPTT is
> also only visible on arm64 at the moment due to being wrapped in a if
> ARM64 in the Kconfig
> 

Fair enough.

> Put another way, I wouldn't expect an arch to have a 'user' visible
> option to enable/disable parsing the PPTT. If an arch can handle
> ACPI/PPTT topology then I would expect it to be fixed to the CONFIG_ACPI
> state. What happens when acpi_find_last_cache_level() is called should
> only be dependent on whether ACPI is enabled, the PPTT parser itself
> will handle the cases of a missing table.

Agreed. But technically that statement is still incorrect as x86 ACPI
build need not have PPTT enabled. IMO you can reword it, but I will
leave that to Rafael :)

Other than that, it looks good.

Acked-by: Sudeep Holla <sudeep.holla@....com>

-- 
Regards,
Sudeep