Subject: [PATCH v2 6/6] arm64: renesas: r8a7795: Add L2 cache-controller nodes

From: [email-masked] (Sudeep Holla)
Date: Tue, 8 Dec 2015 18:58:50 +0000

On 08/12/15 18:50, Dirk Behme wrote:
> On 07.12.2015 20:03, Mark Rutland wrote:
>> On Mon, Dec 07, 2015 at 06:49:43PM +0000, Sudeep Holla wrote:
>>>
>>> On 07/12/15 18:24, Geert Uytterhoeven wrote:
>>>> +    L2_CA57: cache-controller at 0 {
>>>> +        compatible = "cache";
>>>> +        arm,data-latency = <4 4 1>;
>>>> +        arm,tag-latency = <3 3 3>;
>>>
>>> Interesting, only PL2xx/3xx cache controller driver reads this from the
>>> DT and configures the controller. The integrated L2 found in
>>> A15/A7/A57/A53 needs doesn't make use of these values from the DT.
>>
>> These properties seem to be from l2cc.txt, which really only corresponds
>> to PL210/PL220/PL310 (and variants) and isn't as generic as it sounds.
>>
>> I don't see that these are necessary at all.
>
>
> What's about a documentation patch like [1], then?
>
>
> For what is the arm64 dts entry
>
> cpu at 0 {
>      ...
>      next-level-cache = <&L2_0>;
> };
>
> L2_0: l2-cache0 {
>      compatible = "cache";
> };
>
> good for at all, then?
>
>
> Best regards
>
> Dirk
>
>
> [1]
>
> diff --git a/Documentation/devicetree/bindings/arm/l2cc.txt
> b/Documentation/devicetree/bindings/arm/l2cc.txt
> index 06c88a4..f687aed 100644
> --- a/Documentation/devicetree/bindings/arm/l2cc.txt
> +++ b/Documentation/devicetree/bindings/arm/l2cc.txt
> @@ -1,12 +1,18 @@
>   * ARM L2 Cache Controller
>
> -ARM cores often have a separate level 2 cache controller. There are
> various
> +ARM 32-bit cores often have a separate level 2 cache controller. There
> are various
>   implementations of the L2 cache controller with compatible programming
> models.
>   Some of the properties that are just prefixed "cache-*" are taken from
> section
>   3.7.3 of the ePAPR v1.1 specification which can be found at:
>
> https://www.power.org/wp-content/uploads/2012/06/Power_ePAPR_APPROVED_v1.1.pdf
>
>
> -The ARM L2 cache representation in the device tree should be done as
> follows:
> +ARM 64-bit cores (e.g. A15/A7/A57/A53) have an integrated level 2 cache which

A15 and A7 are 32-bit cores, so you can't generalize it.
IMO you can just specify that this binding is applicable for separate L2
cache controllers.

-- 
-- 
Regards,
Sudeep