New patch to review for coreboot: WIP:cpu/x86: allow the number of APs to be specified for running code in parallel to BSP.

[Bora Guvendik]

Bora Guvendik ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/17986

-gerrit

commit eaaf23b76c0b3c2657dfede852bf364417d22409
Author: Bora Guvendik 
Date:   Wed Dec 28 14:46:11 2016 -0800

WIP:cpu/x86: allow the number of APs to be specified for running
    	     code in parallel to BSP.

Allow the number of APs,that will run a piece of code, to be specified.
    In some cases, a single AP needs to run the code alone.

BUG=chrome-os-partner:56656
    BRANCH=reef
    TEST=None

Change-Id: I39d0210886428187cd7c6e75b3473dd5c733842c
    Signed-off-by: Bora Guvendik 
---
 src/cpu/x86/mp_init.c    | 22 ++++++++++++++++++----
 src/include/cpu/x86/mp.h |  3 +++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/cpu/x86/mp_init.c b/src/cpu/x86/mp_init.c
index c989963..57f670b 100644
--- a/src/cpu/x86/mp_init.c
+++ b/src/cpu/x86/mp_init.c
@@ -855,10 +855,11 @@ static void store_callback(mp_callback_t *slot, mp_callback_t value)
    *(volatile mp_callback_t *)slot = value;
 }

-static int run_ap_work(mp_callback_t func, long expire_us)
+static int run_ap_work(mp_callback_t func, long expire_us, int num_aps_needed)
 {
    int i;
    int cpus_accepted;
+	int cpus_signaled = 0;
    struct stopwatch sw;
    int cur_cpu = cpu_index();

@@ -867,11 +868,17 @@ static int run_ap_work(mp_callback_t func, long expire_us)
    	return -1;
    }

+	if ( num_aps_needed > ARRAY_SIZE(ap_callbacks) )
+		return -1;
+
    /* Signal to all the APs to run the func. */
    for (i = 0; i < ARRAY_SIZE(ap_callbacks); i++) {
    	if (cur_cpu == i)
    		continue;
    	store_callback(&ap_callbacks[i], func);
+		cpus_signaled++;
+		if ( cpus_signaled == num_aps_needed )
+			break;
    }
    mfence();

@@ -883,13 +890,15 @@ static int run_ap_work(mp_callback_t func, long expire_us)
    			continue;
    		if (read_callback(&ap_callbacks[i]) == NULL)
    			cpus_accepted++;
+			if ( cpus_accepted == num_aps_needed )
+				break;
    	}
-		if (cpus_accepted == global_num_aps)
+		if (cpus_accepted == num_aps_needed)
    		return 0;
    }

printk(BIOS_ERR, "AP call expired. %d/%d CPUs accepted.\n",
-		cpus_accepted, global_num_aps);
+		cpus_accepted, num_aps_needed);
    return -1;
 }

@@ -916,7 +925,12 @@ static void ap_wait_for_instruction(void)

int mp_run_on_aps(void (*func)(void), long expire_us)
 {
-	return run_ap_work(func, expire_us);
+	return run_ap_work(func, expire_us, ARRAY_SIZE(ap_callbacks));
+}
+
+int mp_run_on_single_ap(void (*func)(void), long expire_us)
+{
+	return run_ap_work(func, expire_us, 1);
 }

int mp_run_on_all_cpus(void (*func)(void), long expire_us)
diff --git a/src/include/cpu/x86/mp.h b/src/include/cpu/x86/mp.h
index b9b4d57..8220530 100644
--- a/src/include/cpu/x86/mp.h
+++ b/src/include/cpu/x86/mp.h
@@ -133,6 +133,9 @@ int mp_init_with_smm(struct bus *cpu_bus, const struct mp_ops *mp_ops);
  */
 int mp_run_on_aps(void (*func)(void), long expire_us);

+/* Like mp_run_on_aps() but runs func on only one ap */
+int mp_run_on_single_ap(void (*func)(void), long expire_us);
+
 /* Like mp_run_on_aps() but also runs func on BSP. */
 int mp_run_on_all_cpus(void (*func)(void), long expire_us);