[PATCH v2] drm/amdgpu/gmc6: fix DMA mask from 44 to 40 bits

[Alex Deucher]

On Thu, Oct 28, 2021 at 11:19 AM Paul Menzel <pmenzel at molgen.mpg.de> wrote:
>
> Dear Alex,
>
>
> On 28.10.21 16:21, Alex Deucher wrote:
> > The DMA mask on SI parts is 40 bits not 44.  Copy
> > paste typo.
> >
> > Fixes: 244511f386ccb9 ("drm/amdgpu: simplify and cleanup setting the dma mask")
>
> This was present in Linux 5.4-rc1. Can it also be the cause of some of
> the crashes with the AMD Ryzen systems like Bug 206487 - Random
> freezes/crashes with enabled C-State C6 - AMD Ryzen [1]? I know, there
> were also some things with Linux 4.19.57, but, if my memory serves
> correctly, they were much more often with Linux 5.4. Some crashes had
> MCE and other did not, some froze the system, some rebooted it.

I doubt it would cause an MCE.  You should just see an IOMMU page fault.

Alex

>
> > Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1762
> > Acked-by: Christian König <christian.koenig at amd.com>
> > Tested-by: Paul Menzel <pmenzel at molgen.mpg.de>
> > Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> > index 0e81e03e9b49..0fe714f54cca 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
> > @@ -841,12 +841,12 @@ static int gmc_v6_0_sw_init(void *handle)
> >
> >       adev->gmc.mc_mask = 0xffffffffffULL;
> >
> > -     r = dma_set_mask_and_coherent(adev->dev, DMA_BIT_MASK(44));
> > +     r = dma_set_mask_and_coherent(adev->dev, DMA_BIT_MASK(40));
> >       if (r) {
> >               dev_warn(adev->dev, "No suitable DMA available.\n");
> >               return r;
> >       }
> > -     adev->need_swiotlb = drm_need_swiotlb(44);
> > +     adev->need_swiotlb = drm_need_swiotlb(40);
> >
> >       r = gmc_v6_0_init_microcode(adev);
> >       if (r) {
> >
>
>
> Kind regards,
>
> Paul
>
>
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=206487