powerpc: use ATB clock, if it's available
The ATB is more precise, but we don't know if it's available.
Check by forking off a process that attempts to use it, if
we die with SIGILL, then we know it's not there.
Based on code from Steven Noonan.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/arch/arch-ppc.h b/arch/arch-ppc.h
index e73093d..7517627 100644
--- a/arch/arch-ppc.h
+++ b/arch/arch-ppc.h
@@ -1,6 +1,11 @@
#ifndef ARCH_PPC_H
#define ARCH_PPH_H
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
#define FIO_ARCH (arch_ppc)
#ifndef __NR_ioprio_set
@@ -43,26 +48,72 @@
return __ilog2(bitmask & -bitmask);
}
+static inline unsigned int mfspr(unsigned int reg)
+{
+ unsigned int val;
+
+ asm volatile("mfspr %0,%1": "=r" (val) : "K" (reg));
+ return val;
+}
+
+#define SPRN_TBRL 0x10C /* Time Base Register Lower */
+#define SPRN_TBRU 0x10D /* Time Base Register Upper */
+#define SPRN_ATBL 0x20E /* Alternate Time Base Lower */
+#define SPRN_ATBU 0x20F /* Alternate Time Base Upper */
+
static inline unsigned long long get_cpu_clock(void)
{
unsigned int tbl, tbu0, tbu1;
unsigned long long ret;
do {
- __asm__ __volatile__ ("mftbu %0" : "=r"(tbu0));
- __asm__ __volatile__ ("mftb %0" : "=r"(tbl) );
- __asm__ __volatile__ ("mftbu %0" : "=r"(tbu1));
+ if (arch_flags & ARCH_FLAG_1) {
+ tbu0 = mfspr(SPRN_ATBU);
+ tbl = mfspr(SPRN_ATBL);
+ tbu1 = mfspr(SPRN_ATBU);
+ } else {
+ __asm__ __volatile__("mftbu %0" : "=r"(tbu0));
+ __asm__ __volatile__("mftb %0" : "=r"(tbl) );
+ __asm__ __volatile__("mftbu %0" : "=r"(tbu1));
+ }
} while (tbu0 != tbu1);
ret = (((unsigned long long)tbu0) << 32) | tbl;
return ret;
}
+static void atb_child(void)
+{
+ arch_flags |= ARCH_FLAG_1;
+ get_cpu_clock();
+ _exit(0);
+}
+
+static void atb_clocktest(void)
+{
+ pid_t pid;
+
+ pid = fork();
+ if (!pid)
+ atb_child();
+ else {
+ int status;
+
+ wait(&status);
+ if (!WIFEXITED(status))
+ arch_flags &= ~ARCH_FLAG_1;
+ else
+ arch_flags |= ARCH_FLAG_1;
+ }
+}
+
#define ARCH_HAVE_INIT
extern int tsc_reliable;
+
static inline int arch_init(char *envp[])
{
tsc_reliable = 1;
+ atb_clocktest();
return 0;
}