linux-kernel - Re: [PATCH v9 1/6] platform-msi: Add msi_remove_device_irq_domain() in platform_device_msi_free_irqs

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Message-ID: <Z1B/CuivEIT9HR8c@lizhi-Precision-Tower-5810>
Date: Wed, 4 Dec 2024 11:10:50 -0500
From: Frank Li <Frank.li@....com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Anup Patel <apatel@...tanamicro.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, imx@...ts.linux.dev,
	Niklas Cassel <cassel@...nel.org>, dlemoal@...nel.org,
	maz@...nel.org, jdmason@...zu.us, stable@...nel.org
Subject: Re: [PATCH v9 1/6] platform-msi: Add msi_remove_device_irq_domain()
 in platform_device_msi_free_irqs_all()

On Wed, Dec 04, 2024 at 12:14:25AM +0100, Thomas Gleixner wrote:
> On Tue, Dec 03 2024 at 16:40, Frank Li wrote:
> > On Tue, Dec 03, 2024 at 10:12:36PM +0100, Thomas Gleixner wrote:
> >> Sure, but that's not a fix and not required for stable because no
> >> existing driver is affected by this unless I'm missing something.
> >>
> >> What's the actual use case for this? You describe in great length what
> >> fails, which is nice, but I'm missing the larger picture here.
> >
> > PCI host send a door bell to PCI endpoint, which use platform msi to
> > trigger a IRQ.
> >
> > PCI Host side				PCI endpoint side
> >
> > Send "enable"  command      ->         call platform_device_msi_init_and_alloc_irqs()
> > Get doorbell address        <-         send back MSI address by shared memory
> > Write data to doorbell      -> 	       MSI irq handler triggered.
> > Send "Disable"  command     ->	       call platform_device_msi_free_irqs_all()
> >
> >
> > At endpoint side, need dymatic response "enable/disable" commands. Of
> > course, I can call msi_remove_device_irq_domain() in my disable function.
> > But I think it should be symetic in alloc/free pair functions.
>
> No objections, but that's not a justification for a stable backport as
> nothing in tree has this problem right now. You add a new use case which
> requires it, so only that new use case has this dependency, no?

Okay, Let me drop fixes and stable tag in next version.

Frank

>
> Thanks,
>
>         tglx