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

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Date:   Wed, 17 Jan 2018 18:20:25 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     Sudeep Holla <sudeep.holla@....com>, 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



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.

-- 
Regards,
Sudeep