Date: Wed, 8 Jul 2015 14:58:23 +0100 From: Andrew Turner <andrew@fubar.geek.nz> To: Zbigniew Bodek <zbb@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r285270 - head/sys/sys Message-ID: <20150708145823.50ae6395@bender> In-Reply-To: <201507081353.t68Dr0up028388@repo.freebsd.org> References: <201507081353.t68Dr0up028388@repo.freebsd.org>
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On Wed, 8 Jul 2015 13:53:00 +0000 (UTC) Zbigniew Bodek <zbb@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(); Should this be a dmb or dsb? mb() is implemented as the former on ARMv7, and as the equivalent using mcr on ARMv6. Only on ARMv4 and ARMv5 is it a dsb. Andrew
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