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-rw-r--r--drivers/misc/sgi-xp/xp_nofault.S36
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diff --git a/drivers/misc/sgi-xp/xp_nofault.S b/drivers/misc/sgi-xp/xp_nofault.S
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+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2008 Silicon Graphics, Inc. All Rights Reserved.
+ */
+
+
+/*
+ * The xp_nofault_PIOR function takes a pointer to a remote PIO register
+ * and attempts to load and consume a value from it. This function
+ * will be registered as a nofault code block. In the event that the
+ * PIO read fails, the MCA handler will force the error to look
+ * corrected and vector to the xp_error_PIOR which will return an error.
+ *
+ * The definition of "consumption" and the time it takes for an MCA
+ * to surface is processor implementation specific. This code
+ * is sufficient on Itanium through the Montvale processor family.
+ * It may need to be adjusted for future processor implementations.
+ *
+ * extern int xp_nofault_PIOR(void *remote_register);
+ */
+
+ .global xp_nofault_PIOR
+xp_nofault_PIOR:
+ mov r8=r0 // Stage a success return value
+ ld8.acq r9=[r32];; // PIO Read the specified register
+ adds r9=1,r9;; // Add to force consumption
+ srlz.i;; // Allow time for MCA to surface
+ br.ret.sptk.many b0;; // Return success
+
+ .global xp_error_PIOR
+xp_error_PIOR:
+ mov r8=1 // Return value of 1
+ br.ret.sptk.many b0;; // Return failure