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From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Tue, 3 Nov 2015 08:42:43 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r290326 - head/sys/dev/usb
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Author: hselasky
Date: Tue Nov  3 08:42:43 2015
New Revision: 290326
URL: https://svnweb.freebsd.org/changeset/base/290326

Log:
  Relax the BUS_DMA_KEEP_PG_OFFSET requirement to allow optimising
  allocation of DMA bounce buffers.
  
  Discussed with:	ian @
  MFC after:	3 weeks

Modified:
  head/sys/dev/usb/usb_busdma.c

Modified: head/sys/dev/usb/usb_busdma.c
==============================================================================
--- head/sys/dev/usb/usb_busdma.c	Tue Nov  3 08:33:24 2015	(r290325)
+++ head/sys/dev/usb/usb_busdma.c	Tue Nov  3 08:42:43 2015	(r290326)
@@ -443,9 +443,13 @@ usb_pc_common_mem_cb(void *arg, bus_dma_
 	pc->page_offset_buf = rem;
 	pc->page_offset_end += rem;
 #ifdef USB_DEBUG
-	if (rem != (USB_P2U(pc->buffer) & (USB_PAGE_SIZE - 1))) {
+	if (nseg > 1 &&
+	    ((segs->ds_addr + segs->ds_len) & (USB_PAGE_SIZE - 1)) !=
+	    ((segs + 1)->ds_addr & (USB_PAGE_SIZE - 1))) {
 		/*
-		 * This check verifies that the physical address is correct:
+		 * This check verifies there is no page offset hole
+		 * between the first and second segment. See the
+		 * BUS_DMA_KEEP_PG_OFFSET flag.
 		 */
 		DPRINTFN(0, "Page offset was not preserved\n");
 		error = 1;