From 6b56a99e942c3c82ba1bc76d7fb0b3a362c520bd Mon Sep 17 00:00:00 2001
From: hselasky <hselasky@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Tue, 10 Feb 2015 13:25:29 +0000
Subject: [PATCH] MFC r278074: Optimise allocation of USB DMA structures. By
 default don't double map allocations if only one element should be allocated
 per page cache. Make one allocation per element compile time configurable.
 Fix a comment while at it.

git-svn-id: svn://svn.freebsd.org/base/stable/10@278510 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/conf/options           |  1 +
 sys/dev/usb/usb_transfer.c | 31 +++++++++++++++++++++++++++----
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/sys/conf/options b/sys/conf/options
index 2d68b750d..33046f707 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -663,6 +663,7 @@ USB_HOST_ALIGN		opt_usb.h
 USB_REQ_DEBUG		opt_usb.h
 USB_TEMPLATE		opt_usb.h
 USB_VERBOSE		opt_usb.h
+USB_DMA_SINGLE_ALLOC	opt_usb.h
 USB_EHCI_BIG_ENDIAN_DESC	opt_usb.h
 U3G_DEBUG		opt_u3g.h
 UKBD_DFLT_KEYMAP	opt_ukbd.h
diff --git a/sys/dev/usb/usb_transfer.c b/sys/dev/usb/usb_transfer.c
index 464e12816..c5815f7ae 100644
--- a/sys/dev/usb/usb_transfer.c
+++ b/sys/dev/usb/usb_transfer.c
@@ -237,7 +237,11 @@ usbd_transfer_setup_sub_malloc(struct usb_setup_params *parm,
 		n_obj = 1;
 	} else {
 		/* compute number of objects per page */
+#ifdef USB_DMA_SINGLE_ALLOC
+		n_obj = 1;
+#else
 		n_obj = (USB_PAGE_SIZE / size);
+#endif
 		/*
 		 * Compute number of DMA chunks, rounded up
 		 * to nearest one:
@@ -273,15 +277,33 @@ usbd_transfer_setup_sub_malloc(struct usb_setup_params *parm,
 		    &parm->curr_xfer->xroot->dma_parent_tag;
 	}
 
-	if (ppc) {
-		*ppc = parm->xfer_page_cache_ptr;
+	if (ppc != NULL) {
+		if (n_obj != 1)
+			*ppc = parm->xfer_page_cache_ptr;
+		else
+			*ppc = parm->dma_page_cache_ptr;
 	}
 	r = count;			/* set remainder count */
 	z = n_obj * size;		/* set allocation size */
 	pc = parm->xfer_page_cache_ptr;
 	pg = parm->dma_page_ptr;
 
-	for (x = 0; x != n_dma_pc; x++) {
+	if (n_obj == 1) {
+	    /*
+	     * Avoid mapping memory twice if only a single object
+	     * should be allocated per page cache:
+	     */
+	    for (x = 0; x != n_dma_pc; x++) {
+		if (usb_pc_alloc_mem(parm->dma_page_cache_ptr,
+		    pg, z, align)) {
+			return (1);	/* failure */
+		}
+		/* Make room for one DMA page cache and "n_dma_pg" pages */
+		parm->dma_page_cache_ptr++;
+		pg += n_dma_pg;
+	    }
+	} else {
+	    for (x = 0; x != n_dma_pc; x++) {
 
 		if (r < n_obj) {
 			/* compute last remainder */
@@ -294,7 +316,7 @@ usbd_transfer_setup_sub_malloc(struct usb_setup_params *parm,
 		}
 		/* Set beginning of current buffer */
 		buf = parm->dma_page_cache_ptr->buffer;
-		/* Make room for one DMA page cache and one page */
+		/* Make room for one DMA page cache and "n_dma_pg" pages */
 		parm->dma_page_cache_ptr++;
 		pg += n_dma_pg;
 
@@ -314,6 +336,7 @@ usbd_transfer_setup_sub_malloc(struct usb_setup_params *parm,
 			}
 			mtx_unlock(pc->tag_parent->mtx);
 		}
+	    }
 	}
 
 	parm->xfer_page_cache_ptr = pc;
-- 
2.45.0