Re: [PATCH v2] r8169: set coherent DMA mask as well as streaming DMA mask

From: Francois Romieu
Date: Fri Oct 14 2016 - 16:58:40 EST

Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> :
> PCI devices that are 64-bit DMA capable should set the coherent
> DMA mask as well as the streaming DMA mask. On some architectures,
> these are managed separately, and so the coherent DMA mask will be
> left at its default value of 32 if it is not set explicitly. This
> results in errors such as
> r8169 Gigabit Ethernet driver 2.3LK-NAPI loaded
> hwdev DMA mask = 0x00000000ffffffff, dev_addr = 0x00000080fbfff000
> swiotlb: coherent allocation failed for device 0000:02:00.0 size=4096
> CPU: 0 PID: 1062 Comm: systemd-udevd Not tainted 4.8.0+ #35
> Hardware name: AMD Seattle/Seattle, BIOS 10:53:24 Oct 13 2016
> on systems without memory that is 32-bit addressable by PCI devices.
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

Acked-by: Francois Romieu <romieu@xxxxxxxxxxxxx>

Unless someone plans to plug an acenic, a 83820 (pci-e gem board, anyone ?)
on top of a pci <-> pci-e adapter on this kind of motherboard, no other
network driver that uses the pci_... dma api exhibits this mixed 32 / 64 bit
support bug. I haven't checked devices with 32 < mask < 64 nor plain DMA api
converted ones.