From 39a72e06bfca1f79c9a07d23d75fda9755f372e9 Mon Sep 17 00:00:00 2001 From: ian Date: Fri, 13 Dec 2013 16:38:21 +0000 Subject: MFC r256637: 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. --- sys/arm/arm/busdma_machdep-v6.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) (limited to 'sys/arm') diff --git a/sys/arm/arm/busdma_machdep-v6.c b/sys/arm/arm/busdma_machdep-v6.c index b4f4110..15329ac 100644 --- a/sys/arm/arm/busdma_machdep-v6.c +++ b/sys/arm/arm/busdma_machdep-v6.c @@ -425,14 +425,21 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment, 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_tag_t dmat, bus_dmamap_t mapp) 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); -- cgit v1.1