Re: [RFCv3][PATCH 3/5] arm64: Implement ARCH_HAS_FORCE_CACHE

[Will Deacon]

On Tue, Sep 13, 2016 at 08:02:20AM -0700, Laura Abbott wrote:
> On 09/13/2016 02:19 AM, Will Deacon wrote:
> >On Mon, Sep 12, 2016 at 02:32:56PM -0700, Laura Abbott wrote:
> >>
> >>arm64 may need to guarantee the caches are synced. Implement versions of
> >>the kernel_force_cache API to allow this.
> >>
> >>Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
> >>---
> >>v3: Switch to calling cache operations directly instead of relying on
> >>DMA mapping.
> >>---
> >> arch/arm64/include/asm/cacheflush.h |  8 ++++++++
> >> arch/arm64/mm/cache.S               | 24 ++++++++++++++++++++----
> >> arch/arm64/mm/flush.c               | 11 +++++++++++
> >> 3 files changed, 39 insertions(+), 4 deletions(-)
> >
> >I'm really hesitant to expose these cache routines as an API solely to
> >support a driver sitting in staging/. I appreciate that there's a chicken
> >and egg problem here, but we *really* don't want people using these routines
> >in preference to the DMA API, and I fear that we'll simply grow a bunch
> >more users of these things if we promote it as an API like you're proposing.
> >
> >Can the code not be contained under staging/, as part of ion?
> >
> 
> I proposed that in V1 and it was suggested I make it a proper API
> 
> http://www.mail-archive.com/driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx/msg47654.html
> http://www.mail-archive.com/driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx/msg47672.html

:/ then I guess we're in disagreement. If ion really needs this stuff
(which I don't fully grok), perhaps we should be exposing something at
a higher level from the architecture, so it really can't be used for
anything other than ion.

Will