Hi Christoph,
On Fri, Dec 14, 2018 at 12:47 PM Christoph Hellwig <hch@xxxxxx> wrote:
On Fri, Dec 14, 2018 at 10:54:32AM +0100, Geert Uytterhoeven wrote:
- page = alloc_pages(flag, order);
+ page = alloc_pages(flag | GFP_ZERO, order);
if (!page)
return NULL;
There's second implementation below, which calls __get_free_pages() and
does an explicit memset(). As __get_free_pages() calls alloc_pages(), perhaps
it makes sense to replace the memset() by GFP_ZERO, to increase consistency?
It would, but this patch really tries to be minimally invasive to just
provide the zeroing everywhere.
Fair enough.
There is plenty of opportunity
to improve the m68k dma allocator if I can get enough reviewers/testers:
- for one the coldfire/nommu case absolutely does not make sense to
me as there is not work done at all to make sure the memory is
mapped uncached despite the architecture implementing cache
flushing for the map interface. So this whole implementation
looks broken to me and will need some major work (I had a previous
discussion with Greg on that which needs to be dug out)
- the "regular" implementation in this patch should probably be replaced
with the generic remapping helpers that have been added for the 4.21
merge window:
http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/0c3b3171ceccb8830c2bb5adff1b4e9b204c1450
Compile tested only patch below:
--
From ade86dc75b9850daf9111ebf9ce15825a6144f2d Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Fri, 14 Dec 2018 12:41:45 +0100
Subject: m68k: use the generic dma coherent remap allocator
This switche to using common code for the DMA allocations, including
potential use of the CMA allocator if configure. Also add a few
comments where the existing behavior seems to be lacking.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Thanks, looks OK to me.
M68k doesn't have many drivers using the DMA framework, as most of them
predated that framework.
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
-void arch_dma_free(struct device *dev, size_t size, void *addr,
- dma_addr_t handle, unsigned long attrs)
+pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
+ unsigned long attrs)
{
- pr_debug("dma_free_coherent: %p, %x\n", addr, handle);
- vfree(addr);
+ /*
+ * XXX: this doesn't seem to handle the sun3 MMU at all.
Sun-3 selects NO_DMA, and this file is compiled for the HAS_DMA case only.
+ */
+ if (CPU_IS_040_OR_060) {
+ pgprot_val(prot) &= ~_PAGE_CACHE040;
+ pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
+ } else {
+ pgprot_val(prot) |= _PAGE_NOCACHE030;
+ }
+ return prot;
}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
