linux-kernel - Re: [PATCH 07/15] drm/amdgpu: use PCI_IRQ_MSI

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Message-ID: <CAHp75Vd1zVt7F2+44EFPHOrCOzexe=mLaiZixqJR9NNK9-wNQg@mail.gmail.com>
Date:   Tue, 2 Jun 2020 17:35:08 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alex Deucher <alexdeucher@...il.com>
Cc:     "Ruhl, Michael J" <michael.j.ruhl@...el.com>,
        David Airlie <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Stankiewicz, Piotr" <piotr.stankiewicz@...el.com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH 07/15] drm/amdgpu: use PCI_IRQ_MSI_TYPES where appropriate

On Tue, Jun 2, 2020 at 5:21 PM Alex Deucher <alexdeucher@...il.com> wrote:
> On Tue, Jun 2, 2020 at 10:00 AM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Tue, Jun 2, 2020 at 4:38 PM Ruhl, Michael J <michael.j.ruhl@...el.com> wrote:
> > > >From: dri-devel <dri-devel-bounces@...ts.freedesktop.org> On Behalf Of
> > > >Piotr Stankiewicz

> > > >               int nvec = pci_msix_vec_count(adev->pdev);
> > > >               unsigned int flags;
> > > >
> > > >-              if (nvec <= 0) {
> > > >+              if (nvec > 0)
> > > >+                      flags = PCI_IRQ_MSI_TYPES;
> > > >+              else
> > > >                       flags = PCI_IRQ_MSI;
> > > >-              } else {
> > > >-                      flags = PCI_IRQ_MSI | PCI_IRQ_MSIX;
> > > >-              }
> > >
> > > Minor nit:
> > >
> > > Is it really necessary to set do this check?  Can flags just
> > > be set?
> > >
> > > I.e.:
> > >         flags = PCI_IRQ_MSI_TYPES;
> > >
> > > pci_alloc_irq_vector() tries stuff in order.  If MSIX is not available,
> > > it will try MSI.
> >
> > That's also what I proposed earlier. But I suggested as well to wait
> > for AMD people to confirm that neither pci_msix_vec_count() nor flags
> > is needed and we can directly supply MSI_TYPES to the below call.
> >
>
> I think it was leftover from debugging and just to be careful.  We had
> some issues when we originally enabled MSI-X on certain boards.  The
> fix was to just allocate a single vector (since that is all we use
> anyway) and we were using the wrong irq (pdev->irq vs
> pci_irq_vector(pdev, 0)).

Do you agree that simple

  nvec = pci_alloc_irq_vectors(adev->pdev, 1, 1, PCI_IRQ_MSI_TYPES);

will work and we can remove that leftover?

-- 
With Best Regards,
Andy Shevchenko