linux-kernel - Re: [PATCH v3 2/4] cacheinfo: Check cache properties are present in DT

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Date:   Thu, 13 Apr 2023 11:16:37 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Pierre Gondois <pierre.gondois@....com>,
        linux-kernel@...r.kernel.org
Cc:     Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Will Deacon <will@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v3 2/4] cacheinfo: Check cache properties are present in
 DT

On 4/13/23 02:14, Pierre Gondois wrote:
> If a Device Tree (DT) is used, the presence of cache properties is
> assumed. Not finding any is not considered. For arm64 platforms,
> cache information can be fetched from the clidr_el1 register.
> Checking whether cache information is available in the DT
> allows to switch to using clidr_el1.
> 
> init_of_cache_level()
> \-of_count_cache_leaves()
> will assume there a 2 cache leaves (L1 data/instruction caches), which
> can be different from clidr_el1 information.
> 
> cache_setup_of_node() tries to read cache properties in the DT.
> If there are none, this is considered a success. Knowing no
> information was available would allow to switch to using clidr_el1.
> 
> Fixes: de0df442ee49 ("cacheinfo: Check 'cache-unified' property to count cache leaves")
> Reported-by: Alexandre Ghiti <alexghiti@...osinc.com>
> Link: https://lore.kernel.org/all/20230404-hatred-swimmer-6fecdf33b57a@spud/
> Signed-off-by: Pierre Gondois <pierre.gondois@....com>

Humm, it would appear that the cache levels and topology is still 
provided, despite the lack of cache properties in the Device Tree which 
is intended by this patch set however we lost the size/ways/sets 
information, could we not complement the missing properties here?

If this is out of the scope of what you are doing:

Tested-by: Florian Fainelli <f.fainelli@...il.com>

Before:

# lscpu -C
NAME ONE-SIZE ALL-SIZE WAYS TYPE        LEVEL SETS PHY-LINE COHERENCY-SIZE
L1d       32K     128K    4 Data            1  128                      64
L1i       32K     128K    2 Instruction     1  256                      64
L2       512K     512K   16 Unified         2  512                      64

After:

# lscpu -C
NAME ONE-SIZE ALL-SIZE WAYS TYPE        LEVEL SETS PHY-LINE COHERENCY-SIZE
L1d                         Data            1
L1i                         Instruction     1
L2                          Unified         2


-- 
Florian