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From: Thomas Gleixner <tglx@linutronix.de>
To: Marc Zyngier <maz@kernel.org>
Cc: Ryder Lee <ryder.lee@mediatek.com>,
	Frank Wunderlich <frank-w@public-files.de>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-mediatek@lists.infradead.org,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Frank Wunderlich <linux@fw-web.de>
Subject: Re: Aw: Re: [PATCH] pci: mediatek: fix warning in msi.h
Date: Tue, 03 Nov 2020 11:31:17 +0100	[thread overview]
Message-ID: <87k0v27mve.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <901c5eb8bbaa3fe53ddc8f65917e48ef@kernel.org>

On Tue, Nov 03 2020 at 09:54, Marc Zyngier wrote:
> On 2020-11-02 22:18, Thomas Gleixner wrote:
>> So we really need some other solution and removing the warning is not 
>> an option. If MSI is enabled then we want to get a warning when a PCI
>> device has no MSI domain associated. Explicitly expressing the PCIE
>> brigde misfeature of not supporting MSI is way better than silently
>> returning an error code which is swallowed anyway.
>
> I don't disagree here, though the PCI_MSI_ARCH_FALLBACKS mechanism
> makes it more difficult to establish.

Only for the few leftovers which implement msi_controller, i.e.

drivers/pci/controller/pci-hyperv.c
drivers/pci/controller/pci-tegra.c
drivers/pci/controller/pcie-rcar-host.c
drivers/pci/controller/pcie-xilinx.c

The architectures which select PCI_MSI_ARCH_FALLBACKS are:

arch/ia64/Kconfig:      select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
arch/mips/Kconfig:      select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
arch/powerpc/Kconfig:   select PCI_MSI_ARCH_FALLBACKS           if PCI_MSI
arch/s390/Kconfig:      select PCI_MSI_ARCH_FALLBACKS   if PCI_MSI
arch/sparc/Kconfig:     select PCI_MSI_ARCH_FALLBACKS if PCI_MSI

implement arch_setup_msi_irq() which makes it magically work :)

>> Whatever the preferred way is via flags at host probe time or flagging
>> it post probe I don't care much as long as it is consistent.
>
> Host probe time is going to require some changes in the core PCI api,
> as everything that checks for a MSI domain is based on the pci_bus
> structure, which is only allocated much later.

Yeah, it's nasty. One possible solution is to add flags or a callback to
pci_ops, but it's not pretty either.

I think we should go with the 'mark it after pci_host_probe()' hack for
5.10-rc. The real fix will be larger and go into 5.11.

Thoughts?

Thanks,

        tglx


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  parent reply	other threads:[~2020-11-03 10:31 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-31 14:03 [PATCH] pci: mediatek: fix warning in msi.h Frank Wunderlich
2020-10-31 21:49 ` Thomas Gleixner
2020-11-01  9:25   ` Frank Wunderlich
2020-11-01 11:17     ` Thomas Gleixner
2020-11-01 11:43     ` Marc Zyngier
2020-11-01 15:58       ` Aw: " Frank Wunderlich
2020-11-01 17:54       ` Ryder Lee
2020-11-01 18:27         ` Aw: " Frank Wunderlich
2020-11-01 21:47           ` Marc Zyngier
2020-11-01 22:27             ` Thomas Gleixner
2020-11-02 11:30               ` Marc Zyngier
2020-11-02 11:56                 ` Aw: " Frank Wunderlich
2020-11-02 13:58                   ` Marc Zyngier
2020-11-02 14:27                     ` Aw: " Frank Wunderlich
2020-11-02 16:16                 ` Aw: " Thomas Gleixner
2020-11-02 22:18                   ` Thomas Gleixner
2020-11-03  9:54                     ` Marc Zyngier
2020-11-03 10:16                       ` Thomas Gleixner
2020-11-03 10:29                         ` Marc Zyngier
2020-11-04 16:49                         ` Aw: " Frank Wunderlich
2020-11-04 23:14                           ` Thomas Gleixner
2020-11-05  9:20                             ` Marc Zyngier
2020-11-05 13:59                               ` Aw: " Frank Wunderlich
2020-11-05 23:00                               ` Aw: " Thomas Gleixner
2020-11-06  9:43                                 ` Marc Zyngier
2020-11-21 16:12                                   ` Aw: " Frank Wunderlich
2021-01-03 13:08                                     ` Frank Wunderlich
2021-02-02 16:21                                   ` Frank Wunderlich
2020-11-03 10:31                       ` Thomas Gleixner [this message]
2020-11-03 11:41                         ` Aw: " Marc Zyngier
2020-11-03 14:23                           ` Thomas Gleixner

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