Blackfin arch: add support for working around anomaly 05000312

Anomaly 05000312 - Errors When SSYNC, CSYNC, or Loads to LT, LB and LC Registers Are Interrupted:

DESCRIPTION:
When instruction cache is enabled, erroneous behavior may occur when any of the following instructions are interrupted:

. CSYNC
• SSYNC
• LCx =
• LTx = (only when LCx is non-zero)
• LBx = (only when LCx is non-zero)

When this problem occurs, a variety of incorrect things could happen, including an illegal instruction exception. Additional errors could
show up as an exception, a hardware error, or an instruction that is valid but different than the one that was expected.

WORKAROUND:
Place a cli before all SSYNC, CSYNC, "LCx =", "LTx =", and "LBx =" instructions to disable interrupts, and place an sti after each of these
instructions to re-enable interrupts. When these instructions are executed in code that is already non-interruptible, the problem will not
occur.
Signed-off-by: NMike Frysinger <michael.frysinger@analog.com>
Signed-off-by: NBryan Wu <bryan.wu@analog.com>

include/asm-blackfin/delay.h

-#ifndef _BLACKFIN_DELAY_H
-#define _BLACKFIN_DELAY_H
-
-static inline void __delay(unsigned long loops)
-{
-
-/* FIXME: Currently the assembler doesn't recognize Loop Register Clobbers,
-   uncomment this as soon those are implemented */
 /*
-      __asm__ __volatile__ (  "\t LSETUP (1f,1f) LC0= %0\n\t"
-                              "1:\t NOP;\n\t"
-                              : :"a" (loops)
-                              : "LT0","LB0","LC0");
+ * delay.h - delay functions
+ *
+ * Copyright (c) 2004-2007 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef __ASM_DELAY_H__
+#define __ASM_DELAY_H__
 
-*/
+#include <asm/mach/anomaly.h>
 
-	__asm__ __volatile__("[--SP] = LC0;\n\t"
-			     "[--SP] = LT0;\n\t"
-			     "[--SP] = LB0;\n\t"
-			     "LSETUP (1f,1f) LC0 = %0;\n\t"
-			     "1:\t NOP;\n\t"
-			     "LB0 = [SP++];\n\t"
-				"LT0 = [SP++];\n\t"
-				"LC0 = [SP++];\n"
-				:
-				:"a" (loops));
+static inline void __delay(unsigned long loops)
+{
+	if (ANOMALY_05000312) {
+		/* Interrupted loads to loop registers -> bad */
+		unsigned long tmp;
+		__asm__ __volatile__(
+			"[--SP] = LC0;"
+			"[--SP] = LT0;"
+			"[--SP] = LB0;"
+			"LSETUP (1f,1f) LC0 = %1;"
+			"1: NOP;"
+			/* We take advantage of the fact that LC0 is 0 at
+			 * the end of the loop.  Otherwise we'd need some
+			 * NOPs after the CLI here.
+			 */
+			"CLI %0;"
+			"LB0 = [SP++];"
+			"LT0 = [SP++];"
+			"LC0 = [SP++];"
+			"STI %0;"
+			: "=d" (tmp)
+			: "a" (loops)
+		);
+	} else
+		__asm__ __volatile__ (
+			"LSETUP(1f, 1f) LC0 = %0;"
+			"1: NOP;"
+			:
+			: "a" (loops)
+			: "LT0", "LB0", "LC0"
+		);
 }
 
 #include <linux/param.h>	/* needed for HZ */
@@ -41,4 +59,4 @@ static inline void udelay(unsigned long usecs)
 	__delay(usecs * loops_per_jiffy / (1000000 / HZ));
 }
 
-#endif				/* defined(_BLACKFIN_DELAY_H) */
+#endif