linux-kernel - Re: [PATCH v2 2/3] cacheinfo: Check cache properties are present in DT

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Date:   Wed, 12 Apr 2023 11:38:30 +0200
From:   Alexandre Ghiti <alexghiti@...osinc.com>
To:     Pierre Gondois <pierre.gondois@....com>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        linux-kernel@...r.kernel.org, Radu Rendec <rrendec@...hat.com>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v2 2/3] cacheinfo: Check cache properties are present in DT

Hi Pierre, Conor,

On Wed, Apr 12, 2023 at 10:12 AM Pierre Gondois <pierre.gondois@....com> wrote:
>
> Hello Conor,
>
> On 4/12/23 09:55, Conor Dooley wrote:
> > Hey Pierre!
> >
> > On Wed, Apr 12, 2023 at 09:18:05AM +0200, 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.
> >
> > Hmm, w/ this series I am still seeing a:
> > [    0.306736] Early cacheinfo failed, ret = -22
> >
> > Not finding any cacheinfo is totally valid, right?
> >
> > A basic RISC-V QEMU setup is sufficient to reproduce, for instance:
> > | $(qemu) \
> > |     -m 2G -smp 5 \
> > |     -M virt -nographic \
> > |     -kernel $(vmlinux_bin)
>
> Sorry I forgot to remove the:
>    pr_err("Early cacheinfo failed, ret = %d\n", ret);

I have just tested it and the messages "cacheinfo: Unable to detect
cache hierarchy for CPU" disappear, I'll add my tested by on the next
version. And just to make sure we agree: this fix should go into
-fixes (for 6.3).

Thanks again Conor and Pierre,

Alex

>
> I ll wait until tomorrow to send a v3 with this fixed.
>
> Thanks for testing,
> Regards,
> Pierre
>
> >
> > Cheers,
> > Conor.
> >