linux-kernel - Re: [PATCH v13 07/13] irqchip/riscv-imsic: Add device MSI domain support for platform devices

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Date: Tue, 20 Feb 2024 22:22:01 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Frank Rowand <frowand.list@...il.com>, 
	Conor Dooley <conor+dt@...nel.org>, Marc Zyngier <maz@...nel.org>, Björn Töpel <bjorn@...nel.org>, 
	Atish Patra <atishp@...shpatra.org>, Andrew Jones <ajones@...tanamicro.com>, 
	Sunil V L <sunilvl@...tanamicro.com>, Saravana Kannan <saravanak@...gle.com>, 
	Anup Patel <anup@...infault.org>, linux-riscv@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH v13 07/13] irqchip/riscv-imsic: Add device MSI domain
 support for platform devices

On Tue, Feb 20, 2024 at 7:02 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Tue, Feb 20 2024 at 11:37, Anup Patel wrote:
> > +#ifdef CONFIG_SMP
> > +static void imsic_msi_update_msg(struct irq_data *d, struct imsic_vector *vec)
> > +{
> > +     struct msi_msg msg[2] = { [1] = { }, };
>
> That's a weird initializer and why do you need an array here?
>
>        struct msi_msg msg = { };
>
> Should be sufficient, no?

I had taken reference from irq_msi_update_msg() in
arch/x86/kernel/apic/msi.c

I tried "struct msi_msg msg = { };" and it works fine so
I will update.

>
> > +
> > +     imsic_irq_compose_vector_msg(vec, msg);
> > +     irq_data_get_irq_chip(d)->irq_write_msi_msg(d, msg);
> > +}
>
> > +static int imsic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> > +                               unsigned int nr_irqs, void *args)
> > +{
> > +     struct imsic_vector *vec;
> > +
> > +     /* Legacy-MSI or multi-MSI not supported yet. */
>
> Coming back to my earlier question:
>
> >> What's legacy MSI in that context?
> >
> > The legacy-MSI is the MSI support in PCI v2.2 where
> > number of MSIs allocated by device were either 1, 2, 4,
> > 8, 16, or 32 and the data written is <data_word> + <irqnum>.
>
> You talk about PCI/MSI, where more than one vector is named
> multi-MSI. Contrary to the modern v3.0 variant which is PCI/MSI-X.
>
> So this should be "Multi-MSI is not supported yet", no?

Yes, I agree. We should just call it "Multi-MSI is not supported yet"
to avoid confusion. I will update.

>
> > +     if (nr_irqs > 1)
> > +             return -ENOTSUPP;
> > +
> > +     vec = imsic_vector_alloc(virq, cpu_online_mask);
> > +     if (!vec)
> > +             return -ENOSPC;
> > +
> > +     irq_domain_set_info(domain, virq, virq,
> > +                         &imsic_irq_base_chip, vec,
> > +                         handle_simple_irq, NULL, NULL);
>
> Please utilize the 100 characters.

Okay, I will update.

>
> > +     irq_set_noprobe(virq);
> > +     irq_set_affinity(virq, cpu_online_mask);
> > +
> > +     return 0;
> > +}
>
> Thanks,
>
>         tglx

Thanks,
Anup