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From: Thomas Gleixner <tglx@linutronix.de>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Paul Walmsley <pjw@kernel.org>,
	Samuel Holland <samuel.holland@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH] irqchip/sifive-plic: use hartid as context_id in OF to fix AMP conflicts
Date: Mon, 20 Oct 2025 19:44:55 +0200	[thread overview]
Message-ID: <87bjm1zcvc.ffs@tglx> (raw)
In-Reply-To: <20251020-fix-plic-amp-v1-1-defe2a99ab80@linux.dev>

On Mon, Oct 20 2025 at 11:49, Troy Mitchell wrote:
> In asymmetric multi-processing (AMP) scenarios, the original PLIC
> driver used the context loop index 'i' as context_id for OF (device

Which original driver and when did it stop to use the context loop index?

> tree) platforms. This caused multiple contexts from different harts
> (e.g., core0 and core4) to share the same enable_base, leading to
> conflicts when initializing the PLIC.

When did it stop to cause the issues? And if the issues have been
already resolved, what is this patch about?

> This patch resolves enable_base conflicts on AMP platforms while

# git grep 'This patch' Documentation/process/

> maintaining SMP/UP behavior.

There is zero explanation what this patch does to resolve the issue.

See also:

  https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#changelog

>  
>  		if (is_of_node(fwnode)) {
> -			context_id = i;
> +			context_id = hartid * 2 + i % 2;

This is incomprehensible and will cause head scratching 6 weeks down the
road. This needs a proper comment with an explanation what this is
about and why it is correct under all circumstances.

Thanks,

        tglx

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http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Paul Walmsley <pjw@kernel.org>,
	Samuel Holland <samuel.holland@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH] irqchip/sifive-plic: use hartid as context_id in OF to fix AMP conflicts
Date: Mon, 20 Oct 2025 19:44:55 +0200	[thread overview]
Message-ID: <87bjm1zcvc.ffs@tglx> (raw)
In-Reply-To: <20251020-fix-plic-amp-v1-1-defe2a99ab80@linux.dev>

On Mon, Oct 20 2025 at 11:49, Troy Mitchell wrote:
> In asymmetric multi-processing (AMP) scenarios, the original PLIC
> driver used the context loop index 'i' as context_id for OF (device

Which original driver and when did it stop to use the context loop index?

> tree) platforms. This caused multiple contexts from different harts
> (e.g., core0 and core4) to share the same enable_base, leading to
> conflicts when initializing the PLIC.

When did it stop to cause the issues? And if the issues have been
already resolved, what is this patch about?

> This patch resolves enable_base conflicts on AMP platforms while

# git grep 'This patch' Documentation/process/

> maintaining SMP/UP behavior.

There is zero explanation what this patch does to resolve the issue.

See also:

  https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#changelog

>  
>  		if (is_of_node(fwnode)) {
> -			context_id = i;
> +			context_id = hartid * 2 + i % 2;

This is incomprehensible and will cause head scratching 6 weeks down the
road. This needs a proper comment with an explanation what this is
about and why it is correct under all circumstances.

Thanks,

        tglx

  reply	other threads:[~2025-10-20 17:45 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-20  3:49 [PATCH] irqchip/sifive-plic: use hartid as context_id in OF to fix AMP conflicts Troy Mitchell
2025-10-20  3:49 ` Troy Mitchell
2025-10-20 17:44 ` Thomas Gleixner [this message]
2025-10-20 17:44   ` Thomas Gleixner
2025-10-21  1:14   ` Troy Mitchell
2025-10-21  1:14     ` Troy Mitchell
2025-10-21 18:23     ` Thomas Gleixner
2025-10-21 18:23       ` Thomas Gleixner
2025-10-23  6:09       ` Troy Mitchell
2025-10-23  6:09         ` Troy Mitchell

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