Re: [v2] PCI: imx: make msi work without pcieportbus
From: Lucas Stach
Date: Thu Dec 13 2018 - 05:07:25 EST
Am Donnerstag, den 13.12.2018, 09:57 +0000 schrieb Richard Zhu:
> Hi Lucas:
> > -----Original Message-----
> > > > From: Lucas Stach [mailto:l.stach@xxxxxxxxxxxxxx]
> > Sent: 2018å12æ13æ 17:19
> > > > > > To: Richard Zhu <hongxing.zhu@xxxxxxx>; bhelgaas@xxxxxxxxxx;
> > lorenzo.pieralisi@xxxxxxx; andrew.smirnov@xxxxxxxxx
> > > > > > Cc: linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx
> > 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
> Âthe 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.