[PATCH Xenial 4.4] UBUNTU: [Config] CONFIG_ZONE_DEVICE=y for amd64

[Mark]

On Sat, January 23, 2016 14:13, Tim Gardner wrote:
> In the event that upstream does not come up with a solution, how about
> if we leave ZONE_DMA enabled in the low-latency flavour ? After all, it
> seems most of the devices that this affects are audio related (except
> for the parallel port).

Another point of information. According to a post in fa.linux.kernel from
2007, some Broadcom NICs may need ZONE_DMA.

https://groups.google.com/forum/#!original/fa.linux.kernel/bXnCP9QIlMI/V6pLHumoe0oJ

"Just because you don't need ISA, doesn't mean you don't need
ZONE_DMA. Various PCI cards have limitations on what addresses they
can DMA to (24 bits on some old PCI sound cards iirc, and more recently
a 30 bit DMA limitation on some Broadcom networking equipment.)"

Another thread mentions the floppy controller, so systems with native
floppy drives could be another casualty:
https://groups.google.com/forum/#!original/fa.linux.kernel/rM_PYJc9ExE/brVe--Xr0FgJ

Is there an easy way to grep the kernel source tree to get a list of all
drivers which depend on ZONE_DMA? I tried that in the drivers subdirectory
and came up with
net/wireless/b43/dma.c
net/wireless/b43legacy/dma.c

Grepping for GFP_DMA returned many more results; someone more
knowledgeable than me might be able to say whether any are relevant.


Mark