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Message-ID: <1544695636.3137.27.camel@pengutronix.de>
Subject: Re: [v2] PCI: imx: make msi work without pcieportbus
From:   Lucas Stach <l.stach@pengutronix.de>
To:     Richard Zhu <hongxing.zhu@nxp.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
        "andrew.smirnov@gmail.com" <andrew.smirnov@gmail.com>
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        <linux-arm-kernel@lists.infradead.org>,
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Date:   Thu, 13 Dec 2018 11:07:16 +0100
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Am Donnerstag, den 13.12.2018, 09:57 +0000 schrieb Richard Zhu:
> Hi Lucas:
> 
> > -----Original Message-----
> > > > From: Lucas Stach [mailto:l.stach@pengutronix.de]
> > Sent: 2018年12月13日 17:19
> > > > > > To: Richard Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com;
> > lorenzo.pieralisi@arm.com; andrew.smirnov@gmail.com
> > > > > > Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> > linux-kernel@vger.kernel.org
> > Subject: Re: [v2] PCI: imx: make msi work without pcieportbus
> > 
> > Hi Richard,
> > 
> > Am Donnerstag, den 13.12.2018, 08:02 +0000 schrieb Richard Zhu:
> > > MSI_EN of iMX PCIe RC would be asserted when PCIEPORTBUS driver is
> > > selected.
> > > Thus, the MSI works fine on iMX PCIe before.
> > > Assert it unconditionally when MSI is supported.
> > > Otherwise, the MSI wouldn't be triggered although the EP is present
> > > and the MSIs are assigned.
> > 
> > Thanks for digging into this issue. This seems like the right way forward.
> > However, did you test this with devices using legacy IRQs?
> > I.e. booting with "nomsi" on the kernel command line to see if legacy IRQs still
> > work if this bit is set, or if we need to avoid setting this when the user
> > explicitly requests to disable MSIs?
> > 
> > Regards,
> > Lucas
> > 
> 
> [Richard Zhu] Thanks for your review.
> The Legacy INTx is broken.
> The MSI_EN bit shouldn't be asserted when the user explicitly requests to disable MSIs.

Okay, so this patch should be extended with a check for
pci_msi_enabled() to see if the user explicitly want legacy IRQs.

> BTW, regarding to Baruch's comments, it seems that all the (IS_ENABLED(CONFIG_PCI_MSI) check in
>  the dwc host drivers are not required anymore, since the depends on PCI_MSI_IRQ_DOMAIN, right?

That's correct. This is mostly a historical artifact from the time when
 we were able to build without MSI support. Those checks could be
cleaned up now that we depend on the MSI options.

Regards,
Lucas