Author: ian Date: Wed Oct 16 16:32:35 2013 New Revision: 256637 URL: http://svnweb.freebsd.org/changeset/base/256637
Log: When calculating the number of bounce pages needed, round the maxsize up to a multiple of PAGE_SIZE, and add one page because there can always be one more boundary crossing than the number of pages in the transfer. Modified: head/sys/arm/arm/busdma_machdep-v6.c Modified: head/sys/arm/arm/busdma_machdep-v6.c ============================================================================== --- head/sys/arm/arm/busdma_machdep-v6.c Wed Oct 16 16:05:49 2013 (r256636) +++ head/sys/arm/arm/busdma_machdep-v6.c Wed Oct 16 16:32:35 2013 (r256637) @@ -425,14 +425,21 @@ bus_dma_tag_create(bus_dma_tag_t parent, if (_bus_dma_can_bounce(newtag->lowaddr, newtag->highaddr) || newtag->alignment > 1) newtag->flags |= BUS_DMA_COULD_BOUNCE; - else - maxsize = 2; /* Need at most 2 bounce pages for unaligned access on cache line boundaries */ + /* + * Any request can auto-bounce due to cacheline alignment, in addition + * to any alignment or boundary specifications in the tag, so if the + * ALLOCNOW flag is set, there's always work to do. + */ if ((flags & BUS_DMA_ALLOCNOW) != 0) { struct bounce_zone *bz; - - /* Must bounce */ - + /* + * Round size up to a full page, and add one more page because + * there can always be one more boundary crossing than the + * number of pages in a transfer. + */ + maxsize = roundup2(maxsize, PAGE_SIZE) + PAGE_SIZE; + if ((error = alloc_bounce_zone(newtag)) != 0) { free(newtag, M_DEVBUF); return (error); @@ -518,20 +525,22 @@ static int allocate_bz_and_pages(bus_dma STAILQ_INIT(&(mapp->bpages)); /* - * Attempt to add pages to our pool on a per-instance - * basis up to a sane limit. + * Attempt to add pages to our pool on a per-instance basis up to a sane + * limit. Even if the tag isn't flagged as COULD_BOUNCE due to + * alignment and boundary constraints, it could still auto-bounce due to + * cacheline alignment, which requires at most two bounce pages. */ if (dmat->flags & BUS_DMA_COULD_BOUNCE) maxpages = MAX_BPAGES; else - maxpages = 2 * bz->map_count; /* Only need at most 2 pages for buffers unaligned on cache line boundaries */ + maxpages = 2 * bz->map_count; if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0 || (bz->map_count > 0 && bz->total_bpages < maxpages)) { int pages; - pages = MAX(atop(dmat->maxsize), 1); + pages = atop(roundup2(dmat->maxsize, PAGE_SIZE)) + 1; pages = MIN(maxpages - bz->total_bpages, pages); - pages = MAX(pages, 1); + pages = MAX(pages, 2); if (alloc_bounce_pages(dmat, pages) < pages) return (ENOMEM); _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"