Re: [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver.

From: Marc Zyngier <maz@kernel.org>
To: Mohamed Mediouni <mohamed.mediouni@caramail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Arnd Bergmann <arnd@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Hector Martin <marcan@marcan.st>,
	linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Stan Skowronek <stan@corellium.com>
Subject: Re: [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver.
Date: Thu, 21 Jan 2021 14:10:28 +0000	[thread overview]
Message-ID: <7131f110736b8a17c824f39abeeaf711@kernel.org> (raw)
In-Reply-To: <2861E21B-32B9-479E-A5F6-528D021183E6@caramail.com>

On 2021-01-21 13:34, Mohamed Mediouni wrote:
>> On 21 Jan 2021, at 14:22, Marc Zyngier <maz@kernel.org> wrote:
>> 
>> On 2021-01-21 12:50, Mohamed Mediouni 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
>> 
>> [...]
>> 
>>>>> +       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.
>> 
>> Then please focus on a single implementation. Additional features can
>> always be merged later once something is up and running.
>> 
>> Also, there sysregs can be detected by matching the MIDR, so I don't
>> think we need a DT property for that.
>> 
>> Thanks,
>> 
> Because UART access adapters for the new M1 Macs aren’t plentiful
> at all, I actually use this for development, with iPhones which have
> much more easy to buy Lightning-to-UART adapters.
> 
> (That’s why the old implementation is there too)
> 
> Might be worth splitting the new one to a new commit though...

This series is supposed to cover M1 only, and adding extra support
as part of it is only likely to make the code harder to review.

I'd rather you focus on a single IPI interface (fast or slow,
I don't really care). Extra features can come in later.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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