svn commit: r285270 - head/sys/sys

[Adrian Chadd]

Why is this implemented in sys/sys/bus_dma.h, rather than in a machdep header?


-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)
>
>  /*
>