linux-kernel - Re: [PATCH v3 14/24] genirq/gic-v3-mbi: Remove unused wired MSI mechanics

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Date: Mon, 17 Jun 2024 16:02:24 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Marc Zyngier <maz@...nel.org>
Cc: Shivamurthy Shastri <shivamurthy.shastri@...utronix.de>,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH v3 14/24] genirq/gic-v3-mbi: Remove unused wired MSI
 mechanics

On Mon, Jun 17 2024 at 14:03, Marc Zyngier wrote:
> On Mon, 17 Jun 2024 13:55:24 +0100,
> Thomas Gleixner <tglx@...utronix.de> wrote:
>> 
>> On Sat, Jun 15 2024 at 18:24, Marc Zyngier wrote:
>> > On Fri, 14 Jun 2024 11:23:53 +0100,
>> > Shivamurthy Shastri <shivamurthy.shastri@...utronix.de> wrote:
>> >>  static struct msi_domain_info mbi_pmsi_domain_info = {
>> >> -	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
>> >> -		   MSI_FLAG_LEVEL_CAPABLE),
>> >> +	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),
>> >>  	.ops	= &mbi_pmsi_ops,
>> >>  	.chip	= &mbi_pmsi_irq_chip,
>> >>  };
>> >
>> > This patch doesn't do what it says. It simply kills any form of level
>> > MSI support for *endpoints*, and has nothing to do with any sort of
>> > "wire to MSI".
>> >
>> > What replaces it?
>> 
>> Patch 9/24 switches the wire to MSI with level support over. This just
>> removes the leftovers.
>
> That's not what I read.
>
> Patch 9/24 rewrites the mbigen driver. Which has nothing to do with
> what the gic-v3-mbi code does. They are different blocks, and the sole
> machine that has the mbigen IP doesn't have any gic-v3-mbi support.
> All they have in common are 3 random letters.
>
> What you are doing here is to kill any support for *devices* that need
> to signal level-triggered MSIs in that driver, and nothing to do with
> wire-MSI translation.
>
> So what replaces it?

Hrm. I must have misread this mess. Let me stare some more.