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

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Date:   Tue, 2 Jun 2020 10:39:47 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Tom St Denis <tom.stdenis@....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 10:35 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> 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?

Yes, I believe so.  Tom, can you give this a quick spin on raven just
in case if you get a chance?  Something like this:

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
index 0cc4c67f95f7..c59111b57cc2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
@@ -248,16 +248,10 @@ int amdgpu_irq_init(struct amdgpu_device *adev)
        adev->irq.msi_enabled = false;

        if (amdgpu_msi_ok(adev)) {
-               int nvec = pci_msix_vec_count(adev->pdev);
-               unsigned int flags;
+               int nvec;

-               if (nvec <= 0) {
-                       flags = PCI_IRQ_MSI;
-               } else {
-                       flags = PCI_IRQ_MSI | PCI_IRQ_MSIX;
-               }
                /* we only need one vector */
-               nvec = pci_alloc_irq_vectors(adev->pdev, 1, 1, flags);
+               nvec = pci_alloc_irq_vectors(adev->pdev, 1, 1,
PCI_IRQ_MSI | PCI_IRQ_MSIX);
                if (nvec > 0) {
                        adev->irq.msi_enabled = true;
                        dev_dbg(adev->dev, "using MSI/MSI-X.\n");


Thanks,

Alex