powerpc/powermac: Constrain 'cpu_sleep()' for AIM to mpc745x

Rename cpu_sleep() to mpc745x_sleep() to denote what it's actually
intended for.  This function is very G4-specific, and will not work on
any other CPU.  This will afterward eliminate a
platform_smp_timebase_sync() call by directly updating the timebase
instead.

(cherry picked from commit b6d8f3b)

sys/powerpc/aim/aim_machdep.c

@@ -721,8 +721,9 @@ flush_disable_caches(void)
 	mtmsr(msr);
 }
 
+#ifndef __powerpc64__
 void
-cpu_sleep()
+mpc745x_sleep()
 {
 	static u_quad_t timebase = 0;
 	static register_t sprgs[4];
@@ -785,3 +786,4 @@ cpu_sleep()
 		enable_vec(curthread);
 	powerpc_sync();
 }
+#endif

sys/powerpc/include/cpu.h

@@ -144,10 +144,14 @@ extern register_t lpcr;
 
 void	cpu_halt(void);
 void	cpu_reset(void);
-void	cpu_sleep(void);
 void	flush_disable_caches(void);
 void	fork_trampoline(void);
 void	swi_vm(void *);
 int	cpu_machine_check(struct thread *, struct trapframe *, int *);
 
+
+#ifndef __powerpc64__
+void	mpc745x_sleep(void);
+#endif
+
 #endif	/* _MACHINE_CPU_H_ */

sys/powerpc/powermac/platform_powermac.c

@@ -68,7 +68,9 @@ static int powermac_smp_get_bsp(platform_t, struct cpuref *cpuref);
 static int powermac_smp_start_cpu(platform_t, struct pcpu *cpu);
 static void powermac_smp_timebase_sync(platform_t, u_long tb, int ap);
 static void powermac_reset(platform_t);
+#ifndef __powerpc64__
 static void powermac_sleep(platform_t);
+#endif
 
 static platform_method_t powermac_methods[] = {
 	PLATFORMMETHOD(platform_probe, 		powermac_probe),
@@ -83,7 +85,9 @@ static platform_method_t powermac_methods[] = {
 	PLATFORMMETHOD(platform_smp_timebase_sync, powermac_smp_timebase_sync),
 
 	PLATFORMMETHOD(platform_reset,		powermac_reset),
+#ifndef __powerpc64__
 	PLATFORMMETHOD(platform_sleep,		powermac_sleep),
+#endif
 
 	PLATFORMMETHOD_END
 };
@@ -404,10 +408,17 @@ powermac_reset(platform_t platform)
 	OF_reboot();
 }
 
+#ifndef __powerpc64__
 void
 powermac_sleep(platform_t platform)
 {
+	/* Only supports MPC745x for now. */
+	if (!MPC745X_P(mfspr(SPR_PVR) >> 16)) {
+		printf("sleep only supported for G4 PowerMac hardware.\n");
+		return;
+	}
 
 	*(unsigned long *)0x80 = 0x100;
-	cpu_sleep();
+	mpc745x_sleep();
 }
+#endif