linux-kernel - Re: [PATCH v6 07/12] drivers: base cacheinfo: Add support for ACPI based firmware tables

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Date:   Tue, 23 Jan 2018 01:11:57 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, jhugo@...eaurora.org,
        wangxiongfeng2@...wei.com, Jonathan.Zhang@...ium.com,
        Al Stone <ahs3@...hat.com>, Jayachandran.Nair@...ium.com,
        austinwc@...eaurora.org, Len Brown <lenb@...nel.org>,
        vkilari@...eaurora.org, Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [PATCH v6 07/12] drivers: base cacheinfo: Add support for ACPI
 based firmware tables

On Mon, Jan 22, 2018 at 10:14 PM, Jeremy Linton <jeremy.linton@....com> wrote:
> Hi,
>
> Thanks for taking a look at this.
>
>
> On 01/22/2018 09:50 AM, Greg KH wrote:
>>
>> On Fri, Jan 12, 2018 at 06:59:15PM -0600, Jeremy Linton wrote:
>>>
>>> Add a entry to to struct cacheinfo to maintain a reference to the PPTT
>>> node which can be used to match identical caches across cores. Also
>>> stub out cache_setup_acpi() so that individual architectures can
>>> enable ACPI topology parsing.
>>>
>>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>>> ---
>>>   drivers/acpi/pptt.c       |  1 +
>>>   drivers/base/cacheinfo.c  | 20 +++++++++++++-------
>>>   include/linux/cacheinfo.h |  9 +++++++++
>>>   3 files changed, 23 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
>>> index 2c4b3ed862a8..4f5ab19c3a08 100644
>>> --- a/drivers/acpi/pptt.c
>>> +++ b/drivers/acpi/pptt.c
>>> @@ -329,6 +329,7 @@ static void update_cache_properties(struct cacheinfo
>>> *this_leaf,
>>>   {
>>>         int valid_flags = 0;
>>>   +     this_leaf->fw_unique = cpu_node;
>>>         if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID) {
>>>                 this_leaf->size = found_cache->size;
>>>                 valid_flags++;
>>> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
>>> index 217aa90fb036..ee51e33cc37c 100644
>>> --- a/drivers/base/cacheinfo.c
>>> +++ b/drivers/base/cacheinfo.c
>>> @@ -208,16 +208,16 @@ static int cache_setup_of_node(unsigned int cpu)
>>>         if (index != cache_leaves(cpu)) /* not all OF nodes populated */
>>>                 return -ENOENT;
>>> -
>>>         return 0;
>>>   }
>>> +
>>
>>
>> Whitespace changes not needed for this patch :(
>
>
> Sure.
>
>
>>
>>
>>>   #else
>>>   static inline int cache_setup_of_node(unsigned int cpu) { return 0; }
>>>   static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
>>>                                            struct cacheinfo *sib_leaf)
>>>   {
>>>         /*
>>> -        * For non-DT systems, assume unique level 1 cache, system-wide
>>> +        * For non-DT/ACPI systems, assume unique level 1 caches,
>>> system-wide
>>>          * shared caches for all other levels. This will be used only if
>>>          * arch specific code has not populated shared_cpu_map
>>>          */
>>> @@ -225,6 +225,11 @@ static inline bool cache_leaves_are_shared(struct
>>> cacheinfo *this_leaf,
>>>   }
>>>   #endif
>>>   +int __weak cache_setup_acpi(unsigned int cpu)
>>> +{
>>> +       return -ENOTSUPP;
>>> +}
>>> +
>>>   static int cache_shared_cpu_map_setup(unsigned int cpu)
>>>   {
>>>         struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
>>> @@ -235,11 +240,11 @@ static int cache_shared_cpu_map_setup(unsigned int
>>> cpu)
>>>         if (this_cpu_ci->cpu_map_populated)
>>>                 return 0;
>>>   -     if (of_have_populated_dt())
>>> +       if (!acpi_disabled)
>>> +               ret = cache_setup_acpi(cpu);
>>
>>
>> Why does acpi go first?  :)
>
>
> This sounds like a joke i heard...
>
> OTOH, given that we have machines with both ACPI and DT tables, it seemed a
> little clearer and a little more robust to code that so that if ACPI is
> enabled to prefer it over DT information. As long as the routines which set
> of of_root are protected by if (acpi_disabled) checks it should be safe to
> do it either way.

I guess adding a comment about that might help.