svn commit: r285270 - head/sys/sys

[Ian Lepore]

On Wed, 2015-07-08 at 07:30 -0700, Adrian Chadd wrote:
> Why is this implemented in sys/sys/bus_dma.h, rather than in a machdep header?
> 
> 

Indeed, this stuff is a mess that really needs to be cleaned up.  The
pre-existing assumption that MI functions don't need to be called, just
because one of the parameters of that function has some value that has a
special meaning on one platform, is purely x86-MD code in an MI header
file.  This change just complicates the existing mess.

> -a
> 
> 
> On 8 July 2015 at 06:53, Zbigniew Bodek <zbb at freebsd.org> wrote:
> > Author: zbb
> > Date: Wed Jul  8 13:52:59 2015
> > New Revision: 285270
> > URL: https://svnweb.freebsd.org/changeset/base/285270
> >
> > Log:
> >   Add memory barrier to bus_dmamap_sync()
> >
> >   On platforms which are fully IO-coherent, the map might be null.
> >   We need to guarantee that all data is observable after the
> >   sync operation is called. Add a memory barrier to ensure that on ARM.
> >
> >   Reviewed by:   andrew, kib
> >   Obtained from: Semihalf
> >   Sponsored by:  The FreeBSD Foundation
> >   Differential Revision: https://reviews.freebsd.org/D3012
> >
> > Modified:
> >   head/sys/sys/bus_dma.h
> >
> > Modified: head/sys/sys/bus_dma.h
> > ==============================================================================
> > --- head/sys/sys/bus_dma.h      Wed Jul  8 13:19:13 2015       (r285269)
> > +++ head/sys/sys/bus_dma.h      Wed Jul  8 13:52:59 2015        (r285270)
> > @@ -282,13 +282,25 @@ int bus_dmamem_alloc(bus_dma_tag_t dmat,
> >  void bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map);
> >
> >  /*
> > - * Perform a synchronization operation on the given map.
> > + * Perform a synchronization operation on the given map. If the map
> > + * is NULL we have a fully IO-coherent system. On every ARM architecture
> > + * there must be a memory barrier placed to ensure that all data
> > + * accesses are visible before going any further.
> >   */
> >  void _bus_dmamap_sync(bus_dma_tag_t, bus_dmamap_t, bus_dmasync_op_t);
> > +#if defined(__arm__)
> > +       #define __BUS_DMAMAP_SYNC_DEFAULT               mb();
> > +#elif defined(__aarch64__)
> > +       #define __BUS_DMAMAP_SYNC_DEFAULT               dmb(sy);
> > +#else
> > +       #define __BUS_DMAMAP_SYNC_DEFAULT               {}
> > +#endif
> >  #define bus_dmamap_sync(dmat, dmamap, op)                      \
> >         do {                                                    \
> >                 if ((dmamap) != NULL)                           \
> >                         _bus_dmamap_sync(dmat, dmamap, op);     \
> > +               else                                            \
> > +                       __BUS_DMAMAP_SYNC_DEFAULT               \
> >         } while (0)
> >
> >  /*
> >
>