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

[Dirk Behme <dirk.behme@gmail.com>]

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@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@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
+doesn't make use of any values from the kernel device tree. There is no
+L2 cache configuration done in the kernel. The L2 cache is assumed to be
+preconfigured by early secure boot code.
+
+The ARM L2 cache representation for 32-bit cores in the device tree 
should be done
+as follows:

  Required properties: