[PATCH] drm/radeon: insist on 32-bit DMA for Cedar

[Alex Deucher]

On Wed, Feb 21, 2018 at 6:41 PM, Ben Crocker <bcrocker at redhat.com> wrote:
> In radeon_device_init, set the need_dma32 flag for Cedar chips
> (e.g. FirePro 2270).  This fixes, or at least works around, a bug
> on PowerPC exposed by last year's commits
>
> 8e3f1b1d8255105f31556aacf8aeb6071b00d469 (Russell Currey)
>
> and
>
> 253fd51e2f533552ae35a0c661705da6c4842c1b (Alistair Popple)
>
> which enabled the 64-bit DMA iommu bypass.
>
> This caused the device to freeze, in some cases unrecoverably, and is
> the subject of several bug reports internal to Red Hat.

Can we make this ppc only?  40 bit DMA works fine on x86.

Alex

>
> Signed-off-by: Ben Crocker <bcrocker at redhat.com>
> ---
>  drivers/gpu/drm/radeon/radeon_device.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index ffc10cadcf34..02538903830d 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1395,7 +1395,10 @@ int radeon_device_init(struct radeon_device *rdev,
>         if (rdev->flags & RADEON_IS_AGP)
>                 rdev->need_dma32 = true;
>         if ((rdev->flags & RADEON_IS_PCI) &&
> -           (rdev->family <= CHIP_RS740))
> +           (rdev->family <= CHIP_RS740 || rdev->family == CHIP_CEDAR))
> +               rdev->need_dma32 = true;
> +       if ((rdev->flags & RADEON_IS_PCIE) &&
> +           (rdev->family == CHIP_CEDAR))
>                 rdev->need_dma32 = true;
>
>         dma_bits = rdev->need_dma32 ? 32 : 40;
> --
> 2.13.6
>
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