From f5a477a34baa2461a9a42a3ecb4783c04ce9201c Mon Sep 17 00:00:00 2001
From: Ian Lepore <ian@FreeBSD.org>
Date: Sun, 2 Mar 2014 19:46:03 +0000
Subject: [PATCH] Add a tunable to set the number of active cores, and enable
 SMP by default.

---
 sys/arm/conf/IMX6               |  2 +-
 sys/arm/freescale/imx/imx6_mp.c | 12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/sys/arm/conf/IMX6 b/sys/arm/conf/IMX6
index 8d418e57efdd..1e08e1f1b263 100644
--- a/sys/arm/conf/IMX6
+++ b/sys/arm/conf/IMX6
@@ -143,7 +143,7 @@ options  	ROOTDEVNAME=\"ufs:mmcsd0s2a\"
 
 # ARM and SoC-specific options
 options  	FDT			# Configure using FDT/DTB data.
-#options  	SMP			# Enable multiple cores
+options  	SMP			# Enable multiple cores
 options  	VFP			# Enable floating point hardware support
 options  	FREEBSD_BOOT_LOADER	# Process metadata passed from loader(8)
 
diff --git a/sys/arm/freescale/imx/imx6_mp.c b/sys/arm/freescale/imx/imx6_mp.c
index 5b5136b61812..dfa435bc149c 100644
--- a/sys/arm/freescale/imx/imx6_mp.c
+++ b/sys/arm/freescale/imx/imx6_mp.c
@@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/bus.h>
+#include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/smp.h>
@@ -72,6 +73,7 @@ void
 platform_mp_setmaxid(void)
 {
 	bus_space_handle_t scu;
+	int hwcpu, ncpu;
 	uint32_t val;
 
 	/* If we've already set the global vars don't bother to do it again. */
@@ -81,10 +83,16 @@ platform_mp_setmaxid(void)
 	if (bus_space_map(fdtbus_bs_tag, SCU_PHYSBASE, SCU_SIZE, 0, &scu) != 0)
 		panic("Couldn't map the SCU\n");
 	val = bus_space_read_4(fdtbus_bs_tag, scu, SCU_CONFIG_REG);
+	hwcpu = (val & SCU_CONFIG_REG_NCPU_MASK) + 1;
 	bus_space_unmap(fdtbus_bs_tag, scu, SCU_SIZE);
 
-	mp_maxid = (val & SCU_CONFIG_REG_NCPU_MASK);
-	mp_ncpus = mp_maxid + 1;
+	ncpu = hwcpu;
+	TUNABLE_INT_FETCH("hw.ncpu", &ncpu);
+	if (ncpu < 1 || ncpu > hwcpu)
+		ncpu = hwcpu;
+
+	mp_ncpus = ncpu;
+	mp_maxid = ncpu - 1;
 }
 
 int