linux-kernel - Re: [PATCH v6 02/12] drivers: base: cacheinfo: setup DT cache properties early

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Message-ID: <6627a9ef-8d62-3cdf-dbea-390770991f30@arm.com>
Date:   Fri, 19 Jan 2018 17:27:21 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        hanjun.guo@...aro.org, lorenzo.pieralisi@....com,
        rjw@...ysocki.net, will.deacon@....com, catalin.marinas@....com,
        gregkh@...uxfoundation.org, viresh.kumar@...aro.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, jhugo@...eaurora.org,
        wangxiongfeng2@...wei.com, Jonathan.Zhang@...ium.com,
        ahs3@...hat.com, Jayachandran.Nair@...ium.com,
        austinwc@...eaurora.org, lenb@...nel.org, vkilari@...eaurora.org,
        morten.rasmussen@....com, Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <albert@...ive.com>
Subject: Re: [PATCH v6 02/12] drivers: base: cacheinfo: setup DT cache
 properties early

Hi,

On 01/18/2018 04:14 AM, Sudeep Holla wrote:
> 
> 
> On 17/01/18 18:51, Jeremy Linton wrote:
>> Hi,
>>
>> On 01/17/2018 12:20 PM, Sudeep Holla wrote:
>>>
>>>
>>> On 16/01/18 21:07, Jeremy Linton wrote:
>>>> Hi,
>>>>
>>>> On 01/15/2018 06:33 AM, Sudeep Holla wrote:
>>>>> On Fri, Jan 12, 2018 at 06:59:10PM -0600, Jeremy Linton wrote:
>>>>>> The original intent in cacheinfo was that an architecture
>>>>>> specific populate_cache_leaves() would probe the hardware
>>>>>> and then cache_shared_cpu_map_setup() and
>>>>>> cache_override_properties() would provide firmware help to
>>>>>> extend/expand upon what was probed. Arm64 was really
>>>>>> the only architecture that was working this way, and
>>>>>> with the removal of most of the hardware probing logic it
>>>>>> became clear that it was possible to simplify the logic a bit.
>>>>>>
>>>>>> This patch combines the walk of the DT nodes with the
>>>>>> code updating the cache size/line_size and nr_sets.
>>>>>> cache_override_properties() (which was DT specific) is
>>>>>> then removed. The result is that cacheinfo.of_node is
>>>>>> no longer used as a temporary place to hold DT references
>>>>>> for future calls that update cache properties. That change
>>>>>> helps to clarify its one remaining use (matching
>>>>>> cacheinfo nodes that represent shared caches) which
>>>>>> will be used by the ACPI/PPTT code in the following patches.
>>>>>>
>>>>>> Cc: Palmer Dabbelt <palmer@...ive.com>
>>>>>> Cc: Albert Ou <albert@...ive.com>
>>>>>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>>>>>> ---
>>>>>>     arch/riscv/kernel/cacheinfo.c |  1 +
>>>>>>     drivers/base/cacheinfo.c      | 65
>>>>>> +++++++++++++++++++------------------------
>>>>>>     include/linux/cacheinfo.h     |  1 +
>>>>>>     3 files changed, 31 insertions(+), 36 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/riscv/kernel/cacheinfo.c
>>>>>> b/arch/riscv/kernel/cacheinfo.c
>>>>>> index 10ed2749e246..6f4500233cf8 100644
>>>>>> --- a/arch/riscv/kernel/cacheinfo.c
>>>>>> +++ b/arch/riscv/kernel/cacheinfo.c
>>>>>> @@ -30,6 +30,7 @@ static void ci_leaf_init(struct cacheinfo
>>>>>> *this_leaf,
>>>>>>             CACHE_WRITE_BACK
>>>>>>             | CACHE_READ_ALLOCATE
>>>>>>             | CACHE_WRITE_ALLOCATE;
>>>>>> +    cache_of_set_props(this_leaf, node);
>>>>>
>>>>> This may be necessary but can it be done as later patch ? So far
>>>>> nothing
>>>>> is added that may break riscv IIUC.
>>>>
>>>> Well I think you have a bisection issue where the additional information
>>>> will disappear between this patch and wherever we put this code back in.
>>>>
>>>
>>> Hmm, I am sorry but I fail to see the issue. Before this change,
>>> populate_cache_leaves just populated the info as per ci_leaf_init in
>>> arch/riscv/kernel/cacheinfo.c and cache_override_properties used to fill
>>> the remaining.
>>>
>>> After this patch, the same is achieved in cache_shared_cpu_map_setup.
>>>
>>> In both case, it was by the end of detect_cache_attributes, so I see no
>>> issue.
>>>
>>
>>
>> Hi,
>>
>> I must be misunderstanding something.
>>
> 
> Looks like I was missing to understand something :)
> 
>> AFAIK, The code in cache_setup_of_node() won't call cache_of_set_props()
>> because it returns when there is an existing of_node (fw_unique) created
>> by the riscv populate_cache_leaves(). That's why I'm making the direct
>> call here. If we fail to get that change in place before
>> cache_override_properties() is removed then the fields not set by the
>> riscv code (size/etc) will be missing.
> 
> Indeed. I am trying to avoid use of cache_of_set_props outside.
> How about skipping setting up of fw_unique in ci_leaf_init instead ?
> 

I've been thinking about this, but I'm hesitant because I don't have a 
good test platform for this code. Plus, I'm not 100% sure that the 
results are the same (is it possible that the platform setup node isn't 
the same as the one the the common code would find?).

I also think I'm getting a little off topic with these patches in 
relation to what the core goal is (adding PPTT parsing).