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

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Date:   Wed, 17 Jan 2018 18:08:27 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Sudeep Holla <sudeep.holla@....com>, jeremy.linton@....com,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        hanjun.guo@...aro.org, lorenzo.pieralisi@....com,
        rjw@...ysocki.net, Will Deacon <will.deacon@....com>,
        catalin.marinas@....com, Greg KH <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,
        albert@...ive.com
Subject: Re: [PATCH v6 02/12] drivers: base: cacheinfo: setup DT cache
 properties early

(Sorry, somehow I missed this email until I saw Jeremy's reply today)

On 15/01/18 16:07, Palmer Dabbelt wrote:
> On Mon, 15 Jan 2018 04:33:38 PST (-0800), sudeep.holla@....com 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.
>>
>> Palmer, Albert,
>>
>> Can you confirm ? Also, as I see we can thin down arch specific
>> implementation on riscv if it's just using DT like ARM64. Sorry if
>> I am missing to see something, so thought of checking.
>>
>> [...]
> 
> Sorry, I guess I'm a bit confused as to what's going on here.  RISC-V
> uses device tree on all Linux systems.
> 

Good. By thin down, I was thinking of moving the init_cache_level and
populate_cache_leaves implementation of riscv to generic weak function
under CONFIG_OF. You may even endup deleting riscv cacheinfo.c

Just a thought, sorry for not being clear earlier.

-- 
Regards,
Sudeep