cpu/x86: Add infinite timeout support into run_ap_work() function

There might be certain requirement in user function where user
might not want to pass any timeout value, in those cases
run_ap_work() should consider infinity as timeout and perform
all APs initialization as per specification.

Set expire_us <= 0 to specify an infinite timeout.

BRANCH=none
BUG=b:74436746
TEST=run_ap_work() is running successfully with 0 expire_us.

Change-Id: Iacd67768c8a120f6a01baaa6817468f6b9a3b764
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/25622
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/x86/mp_init.c

@@ -907,7 +907,9 @@ static int run_ap_work(mp_callback_t func, long expire_us)
 	mfence();
 
 	/* Wait for all the APs to signal back that call has been accepted. */
+	if (expire_us > 0)
 		stopwatch_init_usecs_expire(&sw, expire_us);
+
 	do {
 		cpus_accepted = 0;
 
@@ -920,7 +922,7 @@ static int run_ap_work(mp_callback_t func, long expire_us)
 
 		if (cpus_accepted == global_num_aps)
 			return 0;
-	} while (!stopwatch_expired(&sw));
+	} while (expire_us <= 0 || !stopwatch_expired(&sw));
 
 	printk(BIOS_ERR, "AP call expired. %d/%d CPUs accepted.\n",
 		cpus_accepted, global_num_aps);

src/include/cpu/x86/mp.h

@@ -121,6 +121,9 @@ int mp_init_with_smm(struct bus *cpu_bus, const struct mp_ops *mp_ops);
  * After APs are up and PARALLEL_MP_AP_WORK is enabled one can issue work
  * to all the APs to perform. Currently the BSP is the only CPU that is allowed
  * to issue work. i.e. the APs should not call any of these functions.
+ *
+ * Input parameter expire_us <= 0 to specify an infinite timeout.
+ *
  * All functions return < 0 on error, 0 on success.
  */
 int mp_run_on_aps(void (*func)(void), long expire_us);