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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Marc Zyngier <maz@kernel.org>
Cc:     Frank Wunderlich <frank-w@public-files.de>,
        Ryder Lee <ryder.lee@mediatek.com>,
        linux-mediatek@lists.infradead.org,
        Frank Wunderlich <linux@fw-web.de>,
        linux-kernel@vger.kernel.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: Aw: Re: [PATCH] pci: mediatek: fix warning in msi.h
In-Reply-To: <901c5eb8bbaa3fe53ddc8f65917e48ef@kernel.org>
References: <20201031140330.83768-1-linux@fw-web.de> <878sbm9icl.fsf@nanos.tec.linutronix.de> <EC02022C-64CF-4F4B-A0A2-215A0A49E826@public-files.de> <87lfflti8q.wl-maz@kernel.org> <1604253261.22363.0.camel@mtkswgap22> <trinity-9eb2a213-f877-4af3-87df-f76a9c093073-1604255233122@3c-app-gmx-bap08> <87k0v4u4uq.wl-maz@kernel.org> <87pn4w90hm.fsf@nanos.tec.linutronix.de> <df5565a2f1e821041c7c531ad52a3344@kernel.org> <87h7q791j8.fsf@nanos.tec.linutronix.de> <877dr38kt8.fsf@nanos.tec.linutronix.de> <901c5eb8bbaa3fe53ddc8f65917e48ef@kernel.org>
Date:   Tue, 03 Nov 2020 11:16:56 +0100
Message-ID: <87o8ke7njb.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
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On Tue, Nov 03 2020 at 09:54, Marc Zyngier wrote:
> On 2020-11-02 22:18, Thomas Gleixner wrote:
>> On Mon, Nov 02 2020 at 17:16, Thomas Gleixner wrote:
>>> On Mon, Nov 02 2020 at 11:30, Marc Zyngier wrote:
>>>> --- a/drivers/pci/probe.c
>>>> +++ b/drivers/pci/probe.c
>>>> @@ -871,6 +871,8 @@ static void pci_set_bus_msi_domain(struct pci_bus
>>>> *bus)
>>>>   		d = pci_host_bridge_msi_domain(b);
>>>> 
>>>>   	dev_set_msi_domain(&bus->dev, d);
>>>> +	if (!d)
>>>> +		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
>>> 
>>> Hrm, that might break legacy setups (no irqdomain support). I'd rather
>>> prefer to explicitly tell the pci core at host registration time.
>> 
>> s/might break/ breaks /     Just validated :)
>
> For my own edification, can you point me to the failing case?

Any architecture which selects PCI_MSI_ARCH_FALLBACKS and does not have
irqdomain support runs into:

	if (!d)
		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;

which in turn makes pci_msi_supported() return 0 and consequently makes
pci_enable_msi[x]() fail.

Thanks,

        tglx