Messages in this thread | | | From | Rob Herring <> | Date | Thu, 21 Jan 2021 12:57:34 -0600 | Subject | Re: [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver. |
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On Thu, Jan 21, 2021 at 12:09 PM Mohamed Mediouni <mohamed.mediouni@caramail.com> wrote: > > > > > On 21 Jan 2021, at 18:37, Rob Herring <robh@kernel.org> wrote: > > > > On Thu, Jan 21, 2021 at 10:43 AM Mohamed Mediouni > > <mohamed.mediouni@caramail.com> wrote: > >>> On 21 Jan 2021, at 17:40, Rob Herring <robh@kernel.org> wrote: > >>> On Thu, Jan 21, 2021 at 6:52 AM Mohamed Mediouni > >>> <mohamed.mediouni@caramail.com> wrote: > >>>>> On 21 Jan 2021, at 13:44, Arnd Bergmann <arnd@kernel.org> wrote: > >>>>> On Wed, Jan 20, 2021 at 2:27 PM Mohamed Mediouni > >>>>> <mohamed.mediouni@caramail.com> wrote: > > > > [...] > > > >>>>>> @@ -186,8 +325,11 @@ static int __init apple_aic_init(struct device_node *node, > >>>>>> if (WARN(!aic.base, "unable to map aic registers\n")) > >>>>>> return -EINVAL; > >>>>>> > >>>>>> + aic.fast_ipi = of_property_read_bool(node, "fast-ipi"); > >>>>> > >>>>> Where is this property documented, and what decides which one to use? > >>>> It’s getting documented in the next patch set. > >>>> > >>>> This property is there to enable support for older iPhone processors > >>>> later on, some of which do not have fast IPI support. > >>>> > >>>> On Apple M1, fast-ipi is always on. > >>> > >>> This should be implied by the compatible string which needs to be more > >>> specific and include the SoC name. > >>> > >>> Rob > >> > >> Then we’ll eventually have two aic compatible strings, aic which is compatible > >> with Apple A7 onwards and aicv2 which is a superset with fast IPI (introduced > >> on the Apple A11, 3 years ago, with no further programmer-visible changes since > >> then). > >> > >> Does that look right? > > > > If we did this from the start, it would evolve like this: > > > > A7: "AAPL,a7-aic" > > A8: "AAPL,a8-aic", "AAPL,a7-aic" # Read this as A8 AIC is backwards > > compatible with A7 AIC > > A9: "AAPL,a9-aic", "AAPL,a7-aic" > > > > A11: "AAPL,a11-aic", "AAPL,a7-aic" > > > > If the A11 version could work on an OS that only supported the > > original model (sounds like this is the case) Or if it's not backwards > > compatible: > > > > The A11 AIC indeed can be used by older drivers that aren’t aware > of the fast IPI path introduced on A11 just fine. > > > A11: "AAPL,a11-aic" > > > > If the A11 is different and not backwards compatible. > > > > Then M1 could be: > > > > M1: "AAPL,m1-aic", "AAPL,a11-aic" > > > > Or to even support an OS with only v1 support: > > > > M1: "AAPL,m1-aic", "AAPL,a11-aic", "AAPL,a7-aic" > > > > You don't really need the fallback here because there isn't any > > existing OS support and the baseline is the M1. > > > > If you want to have generic fallback compatible strings with versions, > > that's fine too. I'm not really a fan of version numbers that are just > > made up by the binding author though. Most SoC vendors don't have > > rigorous versioning of their IP and those that do seem to have a new > > version on every SoC. > > > > The important part is *always* having an SoC specific compatible so > > you can deal with any quirk or feature without having to change the > > DTB. Everyone says blocks are 'the same' until they aren’t. > > > Is it fine if such a SoC-specific compatible is present but with having > the driver only know about AAPL,a11-aic for example? > (To just have it when it’d be needed if ever in the future, but not uselessly > add entries to the driver that will not be currently used)
Yes, that's expected. You add the more specific compatible when you add the feature or quirk work-around.
> > On a tangent: > > The internal naming scheme used by Apple is off-by-one: > > Apple A14 for example is Apple H13P (H-series 13th gen processor, Phone) > Apple M1 is Apple H13G (H-series 13th gen, G series) > (And Apple A12X is Apple H11G for example, with A12 being H11P) > > Should we bother with those or use the marketing names? Especially because > the beefier SoCs might not be of the H series anyway… as the internal scheme > reveals that M1 could as well have been an A14X. > > And there’s also the other internal naming scheme: > Apple A12 being t8020, Apple A12X being t8027 > Apple A14 being t8101 > Apple M1 being t8103 > > T there means the foundry at which the chip was manufactured, in the cases above TSMC. > > Of course Apple itself uses both… with the marketing name being nowhere in their device > trees.
I'd probably lean toward the marketing names, but don't really care as long as you're consistent both for a given SoC and across generations.
Rob
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