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List:       freebsd-alpha
Subject:    ATA DMA patch
From:       John Baldwin <jhb () freebsd ! org>
Date:       2007-11-28 19:03:18
Message-ID: 200711281403.18563.jhb () freebsd ! org
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Ok, so I have a patch for the ATA DMA problems relative to the fixes I just
checked into RELENG_6 and RELENG_6_3.  I'd really like to get these tested so
that 6.3 will have working ATA DMA.  I have a PWS machine locally, but it
doesn't have a UDMA controller and I wasn't able to reproduce any corruption
locally.  So to test this can people first verify that they get corruption
with the existing up-to-date RELENG_6 code and then see if this patch makes it
go away?  Note that the workaround is currently only enabled for the CIA
chipsets (such as in the PWS boxes).  I know at least some other boxes (like
some PC164 boxes) also have an issue, but you can test those by forcing
busdma_pyxis_bug to be 1.  If it does work we can come up with some way to
enable the workaround on PC164/2100, etc. boxes as well.

--- //depot/vendor/freebsd_6/src/sys/alpha/alpha/busdma_machdep.c	2007/11/27 17:47:17
+++ //depot/user/jhb/alpha_busdma/sys/alpha/alpha/busdma_machdep.c	2007/11/28 14:21:01
@@ -77,7 +77,7 @@
 	STAILQ_ENTRY(bounce_page) links;
 };
 
-int busdma_swi_pending;
+int busdma_pyxis_bug, busdma_swi_pending;
 
 static struct mtx bounce_lock;
 static STAILQ_HEAD(bp_list, bounce_page) bounce_page_list;
@@ -514,6 +514,22 @@
 	vm_offset_t vaddr;
 	bus_addr_t paddr;
 	int seg;
+	bus_size_t boundary;
+	bus_size_t maxsegsz;
+
+	/*
+	 * Enforce a boundary of 8k for buffers that aren't allocated
+	 * via bus_dmamem_alloc() on systems with the Pyxis pass 1 DMA
+	 * bug.  This is somewhat gross.
+	 */
+	boundary = dmat->boundary;
+	maxsegsz = dmat->maxsegsz;
+	if (busdma_pyxis_bug && map != &nobounce_dmamap) {
+		if (boundary == 0 || boundary > 8192)
+			boundary = 8192;
+		if (boundary < maxsegsz)
+			maxsegsz = boundary;
+	}
 
 	/*
 	 * If we are being called during a callback, pagesneeded will
@@ -566,7 +582,7 @@
 
 	vaddr = (vm_offset_t)buf;
 	lastaddr = *lastaddrp;
-	bmask = ~(dmat->boundary - 1);
+	bmask = ~(boundary - 1);
 
 	for (seg = *segp; buflen > 0 ; ) {
 		/*
@@ -587,8 +603,8 @@
 		/*
 		 * Make sure we don't cross any boundaries.
 		 */
-		if (dmat->boundary > 0) {
-			baddr = (curaddr + dmat->boundary) & bmask;
+		if (boundary > 0) {
+			baddr = (curaddr + boundary) & bmask;
 			if (sgsize > (baddr - curaddr))
 				sgsize = (baddr - curaddr);
 		}
@@ -611,8 +627,8 @@
 			first = 0;
 		} else {
 			if (curaddr == lastaddr &&
-			    (segs[seg].ds_len + sgsize) <= dmat->maxsegsz &&
-			    (dmat->boundary == 0 ||
+			    (segs[seg].ds_len + sgsize) <= maxsegsz &&
+			    (boundary == 0 ||
 			     (segs[seg].ds_addr & bmask) == (curaddr & bmask)))
 				segs[seg].ds_len += sgsize;
 			else {
--- //depot/vendor/freebsd_6/src/sys/alpha/include/md_var.h	2005/12/09 17:45:51
+++ //depot/user/jhb/alpha_busdma/sys/alpha/include/md_var.h	2007/11/25 14:02:05
@@ -50,6 +50,7 @@
 #endif
 extern	long	Maxmem;
 extern	int	busdma_swi_pending;
+extern	int	busdma_pyxis_bug;
 extern struct rpb *hwrpb;
 extern volatile int mc_expected;
 extern volatile int mc_received;
--- //depot/vendor/freebsd_6/src/sys/alpha/pci/cia.c	2005/12/09 17:45:51
+++ //depot/user/jhb/alpha_busdma/sys/alpha/pci/cia.c	2007/11/25 14:02:05
@@ -490,6 +490,7 @@
 		ctrl &= ~(CTRL_RD_TYPE|CTRL_RL_TYPE|CTRL_RM_TYPE);
 		REGVAL(CIA_CSR_CTRL) = ctrl;
 		alpha_mb();
+		busdma_pyxis_bug = 1;
 	}
 #endif
 

-- 
John Baldwin
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