Subject: [Patch] powerpc/cell: make ptcal more reliable

From: [email-masked]
Date: Mon, 04 May 2009 21:32:01 +0200

This is for QS21. The following patch allocates pages only from 
the specified node, moves the ptcal area into the middle of the 
allocated page to avoid potential prefetch problems and prints 
the address of the ptcal area to facilitate diagnostics. 
    
Signed-off-by: Gerhard Stenzel <[email-masked]>

Index: linux-2.6/arch/powerpc/platforms/cell/ras.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/ras.c
+++ linux-2.6/arch/powerpc/platforms/cell/ras.c
@@ -122,12 +122,22 @@ static int __init cbe_ptcal_enable_on_no
 
 	area->nid = nid;
 	area->order = order;
-	area->pages = alloc_pages_node(area->nid, GFP_KERNEL, area->order);
+	area->pages = alloc_pages_node(area->nid, GFP_KERNEL | GFP_THISNODE, area->order);
 
-	if (!area->pages)
+	if (!area->pages) {
+		printk(KERN_INFO "%s: no page on node %d\n",
+			__FUNCTION__, area->nid);
 		goto out_free_area;
+	}
 
-	addr = __pa(page_address(area->pages));
+	/*
+	 * We move the ptcal area to the middle of the allocated
+	 * page, in order to avoid prefetches in memcpy and similar
+	 * functions stepping on it.
+	 */
+	addr = __pa(page_address(area->pages)) + (PAGE_SIZE >> 1);
+	printk(KERN_INFO "%s: enabling PTCAL on node %d address=0x%016lx PAGE_SIZE>>1=0x%016lx \n",
+			__FUNCTION__, area->nid, addr, PAGE_SIZE>>1);
 
 	ret = -EIO;
 	if (rtas_call(ptcal_start_tok, 3, 1, NULL, area->nid,
===================================================================

Best regards, 

Gerhard Stenzel, Linux on Cell Development, LTC
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