(Third try, after turning on Plain Text mode in Gmail; apologies if
you got this more than once)
Hi Greg,
Thanks for the note. I think this is a case of the same change having
been checked in on different branches. I downloaded the linux-4.16.3
tarball, unpacked it, and examined radeon_device.c; the correct change
is there in radeon_device_init (the four lines beginning "#ifdef
CONFIG_PPC64").
Looking at the whole git log, I see two instances of exactly the same
patch:
commit bcb0b981c5571744ac446a6c906aa05a28d21446
Author: Ben Crocker <bcrocker@xxxxxxxxxx>
Date: Thu Feb 22 17:52:19 2018 -0500
drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE
and
commit 2c83029cda55a5e7665c7c6326909427d6a01350
Author: Ben Crocker <bcrocker@xxxxxxxxxx>
Date: Thu Feb 22 17:52:19 2018 -0500
drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE
A colleague of mine here at Red Hat thinks that no further action is
necessary; please let me know what you think.
Thanks,
Ben
On Sun, Apr 22, 2018 at 4:19 AM, <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> The patch below does not apply to the 4.16-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From bcb0b981c5571744ac446a6c906aa05a28d21446 Mon Sep 17 00:00:00 2001
> From: Ben Crocker <bcrocker@xxxxxxxxxx>
> Date: Thu, 22 Feb 2018 17:52:19 -0500
> Subject: [PATCH] drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE
>
> 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.
>
> Signed-off-by: Ben Crocker <bcrocker@xxxxxxxxxx>
> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
>
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 7f40c6f7c4dd..e415d2c097a7 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1366,6 +1366,10 @@ int radeon_device_init(struct radeon_device *rdev,
> if ((rdev->flags & RADEON_IS_PCI) &&
> (rdev->family <= CHIP_RS740))
> rdev->need_dma32 = true;
> +#ifdef CONFIG_PPC64
> + if (rdev->family == CHIP_CEDAR)
> + rdev->need_dma32 = true;
> +#endif
>
> dma_bits = rdev->need_dma32 ? 32 : 40;
> r = pci_set_dma_mask(rdev->pdev, DMA_BIT_MASK(dma_bits));
>