linux-kernel - Re: [PATCH v2 2/7] dt-bindings: interrupt-controller: apple,aic2: New binding for AICv2

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Date:   Mon, 07 Mar 2022 11:35:24 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/7] dt-bindings: interrupt-controller: apple,aic2: New binding for AICv2

On Fri, 25 Feb 2022 21:58:34 +0000,
Hector Martin <marcan@...can.st> wrote:
> 
> On 26/02/2022 05.19, Rob Herring wrote:
> >> +properties:
> >> +  compatible:
> >> +    items:
> >> +      - const: apple,t6000-aic
> >> +      - const: apple,aic2
> > 
> > I feel I was sold on Apple doesn't change h/w and we're the 2nd chip in 
> > and the h/w changed. Just my musings, but aic3 will be rejected. :(
> 
> Well yes, after not changing hardware for N phone/tablet generations,
> they figured out they *finally* had to make some changes for real
> desktop chips... (t8103 was a tablet chip they shoehorned into laptops;
> t6000 is the first real laptop/desktop chip). This isn't the 2nd chip
> in, this is the 26th chip in or so, and yet it's called AIC2 (by Apple
> even)... We aren't starting from chip #1, just the first chip they
> decided to *let* us put Linux on.
> 
> It's pretty clear that the t6000 changes were made with future-proofing
> in mind. I guess we'll find out in a couple weeks, since the rumor mill
> says M2 is coming. If I'm right and we end up needing *zero* kernel
> changes to boot on M2, will you be happy? ;-)
> 
> >> +  apple,event-reg:
> >> +    $ref: /schemas/types.yaml#/definitions/uint32
> >> +    description:
> >> +      Specifies the offset of the event register, which lies after all the
> >> +      implemented die register sets, page aligned. This is not computable from
> >> +      capability register values, so we have to specify it explicitly.
> > 
> > If this is last, then couldn't it be a 2nd 'reg' entry?
> > 
> > 'page aligned' is ambiguous. I assume that means 16K since that's what 
> > Apple uses, but I might assume 4K not knowing that.
> 
> 16K, and yeah, it could be a 2nd reg entry if you think that works
> better. Makes sense.

Do you plan to respin this? If I'm going to that this series for 5.18,
it needs to be this week.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.