linux-kernel - Re: [PATCH v4 2/4] arm64: dts: morello: Add support for common functionalities

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Message-Id: <45E38F12-3585-4AE0-8F05-431DB355FC69@jrtc27.com>
Date: Tue, 7 Jan 2025 14:51:12 +0000
From: Jessica Clarke <jrtc27@...c27.com>
To: Vincenzo Frascino <vincenzo.frascino@....com>
Cc: Rob Herring <robh@...nel.org>,
 devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org,
 Linus Walleij <linus.walleij@...aro.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Liviu Dudau <liviu.dudau@....com>,
 Sudeep Holla <sudeep.holla@....com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH v4 2/4] arm64: dts: morello: Add support for common
 functionalities

On 7 Jan 2025, at 14:34, Vincenzo Frascino <vincenzo.frascino@....com> wrote:
> 
> Hi Jessica,
> 
> Thank you for your review.
> 
> On 07/01/2025 12:56, Jessica Clarke wrote:
>> On Fri, Jan 03, 2025 at 04:14:31PM -0600, Rob Herring wrote:
>>> On Fri, Jan 3, 2025 at 12:16 PM Vincenzo Frascino
>>> <vincenzo.frascino@....com> wrote:
>>>> +       cpus {
>>>> +               #address-cells = <2>;
>>>> +               #size-cells = <0>;
>>>> +
>>>> +               cpu0: cpu@0 {
>>>> +                       compatible = "arm,neoverse-n1";
>>> 
>>> I'm pretty sure the N1 doesn't support CHERI/morello. Perhaps
>>> "arm,neoverse-n1-morello" if we want to capture what it is derived
>>> from and since "arm,morello" is taken already.
>> 
>> Rainier is the codename of the core itself, and Morello LLVM recognises
>> -mcpu=rainier not -mcpu=morello (there's -march=morello instead), so
>> perhaps it should really be "arm,rainier". Though SMBIOS reports it as
>> Morello-R0P1 so it may be best to use "arm,morello" here.
>> 
> 
> We agree on the concept. It should either be "arm,rainier" or "arm,morello-r0p1"

r0p1 isn’t right. Boards with r0p0 and r0p2 CPUs also exist (although
the former are now only within Arm, but the latter are in the wild in
limited numbers, including a couple here at Cambridge).

> if we want to capture the information of SMBIOS. When we reach consensus I will
> update the patches accordingly (Please have a look at my reply to Rob).
> 
>> The real problem is that the board compatible has changed to include a
>> generic "arm,morello" node, with the argument that a v2 board could
>> appear. So why not instead change *that* to be something like:
>> 
>>  compatible = "arm,morello-sdp-v1", "arm,morello-sdp";
>> 
>> Then you can use "arm,morello" here for the cores.>
> 
> The name morello on its own is too overloaded of meaning if we do not specify to
> what we are referring to.
> 
>> Though some of this may depend on what the FVP's DTS looks like; is it
>> going to claim to be a Morello SDP, or does there need to be a common
>> denominator compatible beneath that it can use?
>> 
> 
> I still did not start bringing up to speed the DTS for FVP but I think that we
> should distinguish in between SDP and FVP since not everything is the same,
> hence it should have something similar to:
> 
> compatible = "arm,morello-fvp", "arm,morello";
> 
>> Please CC me on future versions of this series.
>> 
> 
> Will do.
> 
>> Jess
> 
> -- 
> Regards,
> Vincenzo