On Tue, Aug 06, 2019 at 05:45:03PM +0100, Russell King - ARM Linux admin wrote:
> We could have used a different approach, making all IO writes contain
> a "drain write buffer" instruction, and map DMA memory as "buffered",
> but as there were no Linux barriers defined to order memory accesses
> to
On Tue, Aug 06, 2019 at 05:45:03PM +0100, Russell King - ARM Linux admin wrote:
> On Tue, Aug 06, 2019 at 05:08:54PM +0100, Will Deacon wrote:
> > On Sat, Aug 03, 2019 at 08:48:12AM +0200, Christoph Hellwig wrote:
> > > On Fri, Aug 02, 2019 at 11:38:03AM +0100, Will Deacon wrote:
> > > >
> > > > S
On Tue, Aug 06, 2019 at 05:08:54PM +0100, Will Deacon wrote:
> On Sat, Aug 03, 2019 at 08:48:12AM +0200, Christoph Hellwig wrote:
> > On Fri, Aug 02, 2019 at 11:38:03AM +0100, Will Deacon wrote:
> > >
> > > So this boils down to a terminology mismatch. The Arm architecture
> > > doesn't have
> >
On Sat, Aug 03, 2019 at 08:48:12AM +0200, Christoph Hellwig wrote:
> On Fri, Aug 02, 2019 at 11:38:03AM +0100, Will Deacon wrote:
> >
> > So this boils down to a terminology mismatch. The Arm architecture doesn't
> > have
> > anything called "write combine", so in Linux we instead provide what th
On Fri, Aug 02, 2019 at 11:38:03AM +0100, Will Deacon wrote:
>
> So this boils down to a terminology mismatch. The Arm architecture doesn't
> have
> anything called "write combine", so in Linux we instead provide what the Arm
> architecture calls "Normal non-cacheable" memory for pgprot_writecomb
On Fri, Aug 02, 2019 at 10:14:41AM +0200, Christoph Hellwig wrote:
> On Thu, Aug 01, 2019 at 05:44:12PM +0100, Will Deacon wrote:
> > > > Although arch_dma_mmap_pgprot() is a bit of a misnomer now that it only
> > > > gets involved in the non-coherent case.
> > >
> > > A better name is welcome.
>
On Thu, Aug 01, 2019 at 05:44:12PM +0100, Will Deacon wrote:
> > > Although arch_dma_mmap_pgprot() is a bit of a misnomer now that it only
> > > gets involved in the non-coherent case.
> >
> > A better name is welcome.
>
> How about arch_dma_noncoherent_mmap_pgprot() ? Too long?
Sounds a little
On Thu, Aug 01, 2019 at 06:34:57PM +0200, Christoph Hellwig wrote:
> On Thu, Aug 01, 2019 at 05:23:06PM +0100, Will Deacon wrote:
> > > - if (!dev_is_dma_coherent(dev) || (attrs & DMA_ATTR_WRITE_COMBINE))
> > > - return pgprot_writecombine(prot);
> > > - return prot;
> > > + return pgprot_w
On Thu, Aug 01, 2019 at 05:23:06PM +0100, Will Deacon wrote:
> > - if (!dev_is_dma_coherent(dev) || (attrs & DMA_ATTR_WRITE_COMBINE))
> > - return pgprot_writecombine(prot);
> > - return prot;
> > + return pgprot_writecombine(prot);
> > }
>
> Seems like a sensible cleanup to me:
>
On Thu, Aug 01, 2019 at 05:21:18PM +0300, Christoph Hellwig wrote:
> All the way back to introducing dma_common_mmap we've defaulyed to mark
> the pages as uncached. But this is wrong for DMA coherent devices or
> if using DMA_ATTR_NON_CONSISTENT. Later on DMA_ATTR_WRITE_COMBINE
> also got incorr
All the way back to introducing dma_common_mmap we've defaulyed to mark
the pages as uncached. But this is wrong for DMA coherent devices or
if using DMA_ATTR_NON_CONSISTENT. Later on DMA_ATTR_WRITE_COMBINE
also got incorrect treatment as that flag is only treated special on
the alloc side for no
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