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Date:      Tue, 27 May 2014 21:31:11 +0000 (UTC)
From:      Scott Long <scottl@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r266775 - head/sys/x86/x86
Message-ID:  <201405272131.s4RLVBEU035321@svn.freebsd.org>
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Author: scottl
Date: Tue May 27 21:31:11 2014
New Revision: 266775
URL: http://svnweb.freebsd.org/changeset/base/266775

Log:
  Eliminate the fake contig_dmamap and replace it with a new flag,
  BUS_DMA_KMEM_ALLOC.  They serve the same purpose, but using the flag
  means that the map can be NULL again, which in turn enables significant
  optimizations for the common case of no bouncing.
  
  Obtained from:	Netflix, Inc.
  MFC after:	3 days

Modified:
  head/sys/x86/x86/busdma_bounce.c

Modified: head/sys/x86/x86/busdma_bounce.c
==============================================================================
--- head/sys/x86/x86/busdma_bounce.c	Tue May 27 20:45:15 2014	(r266774)
+++ head/sys/x86/x86/busdma_bounce.c	Tue May 27 21:31:11 2014	(r266775)
@@ -62,6 +62,7 @@ __FBSDID("$FreeBSD$");
 enum {
 	BUS_DMA_COULD_BOUNCE	= 0x01,
 	BUS_DMA_MIN_ALLOC_COMP	= 0x02,
+	BUS_DMA_KMEM_ALLOC	= 0x04,
 };
 
 struct bounce_zone;
@@ -125,7 +126,7 @@ struct bus_dmamap {
 
 static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
 static STAILQ_HEAD(, bus_dmamap) bounce_map_callbacklist;
-static struct bus_dmamap nobounce_dmamap, contig_dmamap;
+static struct bus_dmamap nobounce_dmamap;
 
 static void init_bounce_pages(void *dummy);
 static int alloc_bounce_zone(bus_dma_tag_t dmat);
@@ -346,7 +347,7 @@ static int
 bounce_bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
 
-	if (map != NULL && map != &nobounce_dmamap && map != &contig_dmamap) {
+	if (map != NULL && map != &nobounce_dmamap) {
 		if (STAILQ_FIRST(&map->bpages) != NULL) {
 			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
 			    __func__, dmat, EBUSY);
@@ -420,13 +421,13 @@ bounce_bus_dmamem_alloc(bus_dma_tag_t dm
 		*vaddr = (void *)kmem_alloc_attr(kernel_arena,
 		    dmat->common.maxsize, mflags, 0ul, dmat->common.lowaddr,
 		    attr);
-		*mapp = &contig_dmamap;
+		dmat->bounce_flags |= BUS_DMA_KMEM_ALLOC;
 	} else {
 		*vaddr = (void *)kmem_alloc_contig(kernel_arena,
 		    dmat->common.maxsize, mflags, 0ul, dmat->common.lowaddr,
 		    dmat->common.alignment != 0 ? dmat->common.alignment : 1ul,
 		    dmat->common.boundary, attr);
-		*mapp = &contig_dmamap;
+		dmat->bounce_flags |= BUS_DMA_KMEM_ALLOC;
 	}
 	if (*vaddr == NULL) {
 		CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
@@ -449,18 +450,18 @@ bounce_bus_dmamem_free(bus_dma_tag_t dma
 {
 	/*
 	 * dmamem does not need to be bounced, so the map should be
-	 * NULL if malloc() was used and contig_dmamap if
-	 * kmem_alloc_contig() was used.
+	 * NULL and the BUS_DMA_KMEM_ALLOC flag cleared if malloc()
+	 * was used and set if kmem_alloc_contig() was used.
 	 */
-	if (!(map == NULL || map == &contig_dmamap))
+	if (map != NULL)
 		panic("bus_dmamem_free: Invalid map freed\n");
-	if (map == NULL)
+	if ((dmat->bounce_flags & BUS_DMA_KMEM_ALLOC) == 0)
 		free(vaddr, M_DEVBUF);
 	else
 		kmem_free(kernel_arena, (vm_offset_t)vaddr,
 		    dmat->common.maxsize);
 	CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat,
-	    dmat->common.flags);
+	    dmat->bounce_flags);
 }
 
 static void
@@ -612,7 +613,7 @@ bounce_bus_dmamap_load_phys(bus_dma_tag_
 	bus_addr_t curaddr;
 	int error;
 
-	if (map == NULL || map == &contig_dmamap)
+	if (map == NULL)
 		map = &nobounce_dmamap;
 
 	if (segs == NULL)
@@ -665,7 +666,7 @@ bounce_bus_dmamap_load_buffer(bus_dma_ta
 	vm_offset_t vaddr;
 	int error;
 
-	if (map == NULL || map == &contig_dmamap)
+	if (map == NULL)
 		map = &nobounce_dmamap;
 
 	if (segs == NULL)
@@ -976,7 +977,7 @@ add_bounce_page(bus_dma_tag_t dmat, bus_
 	struct bounce_page *bpage;
 
 	KASSERT(dmat->bounce_zone != NULL, ("no bounce zone in dma tag"));
-	KASSERT(map != NULL && map != &nobounce_dmamap && map != &contig_dmamap,
+	KASSERT(map != NULL && map != &nobounce_dmamap,
 	    ("add_bounce_page: bad map %p", map));
 
 	bz = dmat->bounce_zone;

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