Re: [PATCH 2/2] arm64: dts: r8a7795: Add L2 cache-controller nodes

[Sudeep Holla <sudeep.holla@arm.com>]

On 18/12/15 13:33, Geert Uytterhoeven wrote:
> Hi Dirk,
>
> On Fri, Dec 18, 2015 at 12:56 PM, Dirk Behme <dirk.behme@gmail.com> wrote:
>> On 18.12.2015 12:03, Geert Uytterhoeven wrote:
>>> On Sat, Dec 12, 2015 at 8:16 AM, Dirk Behme <dirk.behme@gmail.com> wrote:
>>>> From: Geert Uytterhoeven <geert+renesas@glider.be>
>>>>
>>>> Add device nodes for the L2 caches, and link the CPU node to its L2
>>>> cache node.
>>>>
>>>> The L2 cache for the Cortex-A57 CPU cores is 2 MiB large (organized as
>>>> 128 KiB x 16 ways).
>>>>
>>>> The L2 cache for the Cortex-A53 CPU cores is 512 KiB large (organized as
>>>> 32 KiB x 16 ways).
>>>>
>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>>> Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
>>>> ---
>>>> Note: Geert: I picked your patch from
>>>>
>>>> http://www.spinics.net/lists/arm-kernel/msg466628.html
>>>>
>>>> incoporated some review comments and rebased it against
>>>>
>>>> https://git.kernel.org/cgit/linux/kernel/git/horms/renesas.git/log/?h=next
>>>> renesas-next-20151211v2-v4.4-rc1
>>>
>>> This is more or less what I have locally, except that I kept the latency
>>> properties
>>
>> Hmm, maybe I missed anything, but the only part reading the latency I can
>> find is
>>
>> arch/arm/mm/cache-l2x0.c
>>
>> [1] which isn't relevant for arm64?
>
> No driver using a property in DT is not a reason not to put the property in DT.
> The r8a7995 datasheet does contain the latency values to use.
>

While I agree with that, I would avoid having these values for 2 reasons:

1. Others might blindly copy and expect these setting to done in Linux
    or any non-secure OS using DT which is clearly not possible on ARM64

2. Going by your argument, we usually have much more in datasheets
    which are not all in DT, so strictly speaking that's not a reason to
    have it here.

Again I am not against it, just an opinion.

-- 
Regards,
Sudeep