*
*/
-/* There exist multiprocessor SoC ARM processors, so this matters. */
-/* This needs to be augmented for later ARM (e.g. V7) procesors. */
+#include "../read_ordered.h"
+
+#include "../test_and_set_t_is_ao_t.h" /* Probably suboptimal */
+
+/* NEC LE-IT: ARMv6 is the first architecture providing support for simple LL/SC
+ * A data memory barrier must be raised via CP15 command (see documentation).
+ *
+ * ARMv7 is compatible to ARMv6 but has a simpler command for issuing a
+ * memory barrier (DMB). Raising it via CP15 should still work as told me by the
+ * support engineers. If it turns out to be much quicker than we should implement
+ * custom code for ARMv7 using the asm { dmb } command.
+ *
+ * If only a single processor is used, we can define AO_UNIPROCESSOR
+ * and do not need to access CP15 for ensuring a DMB
+*/
+
+/* NEC LE-IT: gcc has no way to easily check the arm architecture
+ * but defines only one of __ARM_ARCH_x__ to be true */
+#if defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_7__)
+AO_INLINE void
+AO_nop_full()
+{
+#ifndef AO_UNIPROCESSOR
+ /* issue an data memory barrier (keeps ordering of memory transactions */
+ /* before and after this operation) */
+ unsigned int dest=0;
+ __asm__ __volatile__("mcr p15,0,%0,c7,c10,5" :"=&r"(dest) : : "memory");
+#endif
+}
+
+#define AO_HAVE_nop_full
+
+/* NEC LE-IT: AO_t load is simple reading */
+AO_INLINE AO_t
+AO_load(volatile AO_t *addr)
+{
+ /* Cast away the volatile for architectures like IA64 where */
+ /* volatile adds barrier semantics. */
+ return (*(AO_t *)addr);
+}
+#define AO_HAVE_load
+
+/* NEC LE-IT: atomic "store" - according to ARM documentation this is
+ * the only safe way to set variables also used in LL/SC environment.
+ * A direct write won't be recognized by the LL/SC construct on the _same_ CPU.
+ * Support engineers response for behaviour of ARMv6:
+ *
+ Core1 Core2 SUCCESS
+ ===================================
+ LDREX(x)
+ STREX(x) Yes
+ -----------------------------------
+ LDREX(x)
+ STR(x)
+ STREX(x) No
+ -----------------------------------
+ LDREX(x)
+ STR(x)
+ STREX(x) Yes
+ -----------------------------------
+
+ * ARMv7 behaves similar, see documentation CortexA8 TRM, point 8.5
+ *
+ * HB: I think this is only a problem if interrupt handlers do not clear
+ * the reservation, as they almost certainly should. Probably change this back
+ * in a while?
+*/
+AO_INLINE void AO_store(volatile AO_t *addr, AO_t value)
+{
+ unsigned long tmp;
+
+ __asm__ __volatile__("@AO_store\n"
+"1: ldrex %0, [%1]\n"
+" strex %0, %2, [%1]\n"
+" teq %0, #0\n"
+" bne 1b"
+ : "=&r"(tmp)
+ : "r" (addr), "r"(value)
+ : "cc","memory");
+}
+#define AO_HAVE_store
+
+/* NEC LE-IT: replace the SWAP as recommended by ARM:
+
+ "Applies to: ARM11 Cores
+ Though the SWP instruction will still work with ARM V6 cores, it is
+ recommended to use the new V6 synchronization instructions. The SWP
+ instruction produces ‘locked’ read and write accesses which are atomic,
+ i.e. another operation cannot be done between these locked accesses which
+ ties up external bus (AHB,AXI) bandwidth and can increase worst case
+ interrupt latencies. LDREX,STREX are more flexible, other instructions can
+ be done between the LDREX and STREX accesses.
+ "
+*/
+AO_INLINE AO_TS_t
+AO_test_and_set(volatile AO_TS_t *addr) {
+
+ AO_TS_t oldval;
+ unsigned long tmp;
+
+ __asm__ __volatile__("@AO_test_and_set\n"
+"1: ldrex %0, [%2]\n"
+" strex %1, %3, [%2]\n"
+" teq %1, #0\n"
+" bne 1b\n"
+ : "=&r"(oldval),"=&r"(tmp)
+ : "r"(addr), "r"(1)
+ : "memory","cc");
+
+ return oldval;
+}
+
+#define AO_HAVE_test_and_set
+
+/* NEC LE-IT: fetch and add for ARMv6 */
+AO_INLINE AO_t
+AO_fetch_and_add(volatile AO_t *p, AO_t incr)
+{
+ unsigned long tmp,tmp2;
+ AO_t result;
+
+ __asm__ __volatile__("@AO_fetch_and_add\n"
+"1: ldrex %0, [%4]\n" /* get original */
+" add %2, %3, %0\n" /* sum up */
+" strex %1, %2, [%4]\n" /* store them */
+" teq %1, #0\n"
+" bne 1b\n"
+ : "=&r"(result),"=&r"(tmp),"=&r"(tmp2)
+ : "r"(incr), "r"(p)
+ : "cc","memory");
+
+ return result;
+}
+
+#define AO_HAVE_fetch_and_add
+
+/* NEC LE-IT: fetch and add1 for ARMv6 */
+AO_INLINE AO_t
+AO_fetch_and_add1(volatile AO_t *p)
+{
+ unsigned long tmp,tmp2;
+ AO_t result;
+
+ __asm__ __volatile__("@AO_fetch_and_add1\n"
+"1: ldrex %0, [%3]\n" /* get original */
+" add %1, %0, #1\n" /* increment */
+" strex %2, %1, [%3]\n" /* store them */
+" teq %2, #0\n"
+" bne 1b\n"
+ : "=&r"(result), "=&r"(tmp), "=&r"(tmp2)
+ : "r"(p)
+ : "cc","memory");
+
+ return result;
+}
+
+#define AO_HAVE_fetch_and_add1
+
+/* NEC LE-IT: fetch and sub for ARMv6 */
+AO_INLINE AO_t
+AO_fetch_and_sub1(volatile AO_t *p)
+{
+ unsigned long tmp,tmp2;
+ AO_t result;
+
+ __asm__ __volatile__("@ AO_fetch_and_sub1\n"
+"1: ldrex %0, [%3]\n" /* get original */
+" sub %1, %0, #1\n" /* increment */
+" strex %2, %1, [%3]\n" /* store them */
+" teq %2, #0\n"
+" bne 1b\n"
+ : "=&r"(result), "=&r"(tmp), "=&r"(tmp2)
+ : "r"(p)
+ : "cc","memory");
+
+ return result;
+}
+
+#define AO_HAVE_fetch_and_sub1
+/* NEC LE-IT: compare and swap */
+/* Returns nonzero if the comparison succeeded. */
+AO_INLINE int
+AO_compare_and_swap(volatile AO_t *addr,
+ AO_t old_val, AO_t new_val)
+{
+ AO_t result,tmp;
+
+ __asm__ __volatile__("@ AO_compare_and_swap\n"
+"1: ldrex %1, [%2]\n" /* get original */
+" mov %0, #2\n" /* store a flag */
+" teq %1, %3\n" /* see if match */
+" strexeq %0, %4, [%2]\n" /* store new one if matched */
+" teq %0, #1\n"
+" beq 1b\n" /* if update failed, repeat */
+" eor %0, %0, #2\n" /* if succeded, return 2, else 0 */
+ : "=&r"(result), "=&r"(tmp)
+ : "r"(addr), "r"(old_val), "r"(new_val)
+ : "cc","memory");
+
+ return (result>>1);
+}
+#define AO_HAVE_compare_and_swap
+
+#else
+/* pre ARMv6 architecures ... */
+
/* I found a slide set that, if I read it correctly, claims that */
/* Loads followed by either a Load or Store are ordered, but nothing */
/* else is. */
/* It appears that SWP is the only simple memory barrier. */
#include "../all_atomic_load_store.h"
-#include "../read_ordered.h"
-
-#include "../test_and_set_t_is_ao_t.h" /* Probably suboptimal */
-
-
AO_INLINE AO_TS_VAL_t
AO_test_and_set_full(volatile AO_TS_t *addr) {
AO_TS_VAL_t oldval;
#define AO_HAVE_test_and_set_full
-
-
+#endif // __ARM_ARCH_x
projects / cacao.git / blobdiff