linux-kernel - Re: [PATCH] arm64: Make L1_CACHE

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Message-ID: <126b2cc2-a61e-b30d-1ff9-ea30af7abf57@gmail.com>
Date:   Mon, 12 Feb 2018 16:17:44 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Timur Tabi <timur@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org
Cc:     tchalamarla@...ium.com, rrichter@...ium.com, opendmb@...il.com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: Make L1_CACHE_SHIFT configurable

On 02/12/2018 04:10 PM, Timur Tabi wrote:
> On 02/12/2018 05:57 PM, Florian Fainelli wrote:
>> That is debatable, is there a good publicly available table of what the
>> typical L1 cache line size is on ARMv8 platforms?
> 
> I don't have that, but I was under the impression that we moved from 6
> to 7 because more and more ARMv8 platforms have 128-byte caches, so that
> is the "new normal".
> 

That does not seem to be the data that I am collecting from ARM's
website and some quick googling:

The following cores appear to have a 64bytes L1D cache line size: A55,
A73 (fixed), A35, A32, A53, A57 (fixed), A72 (fixed) even the Falkor
seems to be that way according to [1].

APM Mustang also seems to be 64b L1D according to [2].

[1]: https://en.wikichip.org/wiki/qualcomm/microarchitectures/falkor
[2]: http://www.7-cpu.com/cpu/X-Gene.html

And then we seem to covering what the ARM64 mainline kernel knows about
non-ARM implementations: ThunderX and ThunderX2 (formerly Broadcom
Vulcan). There is possibly the Qualcomm Kryo is different, but wikipedia
seems to suggest it is a derivative of existing Cortex-A CPUs which have
a 64b cache line size.

Let's see what Catalin and Will think about what the default should be.

Thanks!
-- 
Florian