linux-kernel - Re: [PATCH 1/3] ARM: uniphier: add outer cache support

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Date:	Tue, 8 Sep 2015 15:09:54 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Jungseung Lee <js07.lee@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	"arm@...nel.org" <arm@...nel.org>, Jiri Slaby <jslaby@...e.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Joe Perches <joe@...ches.com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Paul Bolle <pebolle@...cali.nl>,
	Greg KH <gregkh@...uxfoundation.org>,
	Nathan Lynch <nathan_lynch@...tor.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Kumar Gala <galak@...eaurora.org>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/3] ARM: uniphier: add outer cache support

On Fri, Aug 28, 2015 at 12:24 PM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> 2015-08-26 22:39 GMT+09:00 Linus Walleij <linus.walleij@...aro.org>:

>> cache-unified and cache-level are *not* optional and should be required.
>
> "cache-unified" is mentioned in "3.7.3 Internal (L1) Cache Properties"
> (Table 3-8),
> but it is not in "3.8 Multi-level and Shared Caches" (Table 3-9)
>
> Are the rules in Table 3-8 also applied for L2?

Your guess is as good as mine unless someone involved in
actually writing that spec says something :/

>> (I'm just assuming this cache is unified, anything else would be baffling.)
>
> In fact, unified/harvard is configurable thru a register of this cache
> controller.

Jesus Christ.

> It is usually used as a unified cached, though.

I would, too.

> So,I am planning to use the same compatible for L2 and L3, like this:
>
>
>        l2-cache@...c0000 {
>                compatible = "socionext,uniphier-cache";
>                reg = <0x500c0000 0x2000>, <0x503c0100 0x8>,
>                      <0x506c0000 0x400>;
>                cache-unified;
>                cache-level = <2>;
>                next-level-cache = <&L2>;
>                cache-size = <0x200000>;
>                cache-sets = <256>;
>                cache-line-size = <128>;
>             };
>
>        /* Not all of UniPhier SoCs have L3 cache */
>        l3-cache@...c8000 {
>                compatible = "socionext,uniphier-cache";
>                reg = <0x500c8000 0x2000>, <0x503c8100 0x8>,
>                      <0x506c8000 0x400>;
>                cache-unified;
>                cache-level = <3>;
>                cache-size = <0x400000>;
>                cache-sets = <256>;
>                cache-line-size = <256>;
>        };

This LooksGoodToMe.

> The Table 3-9 in ePAPR v1.1 says
> the compatible should be "cache", but I do not think it makes sense here.

Agree.

Yours,
Linus Walleij
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