ARM: mmp: add SMP support

Used to bring up the second core on MMP3.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

arch/arm/mach-mmp/Makefile

@@ -22,6 +22,9 @@ ifeq ($(CONFIG_PM),y)
 obj-$(CONFIG_CPU_PXA910)	+= pm-pxa910.o
 obj-$(CONFIG_CPU_MMP2)		+= pm-mmp2.o
 endif
+ifeq ($(CONFIG_SMP),y)
+obj-$(CONFIG_MACH_MMP3_DT)	+= platsmp.o
+endif
 
 # board support
 obj-$(CONFIG_MACH_ASPENITE)	+= aspenite.o

arch/arm/mach-mmp/platsmp.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2019 Lubomir Rintel <lkundrak@v3.sk>
+ */
+#include <linux/io.h>
+#include <asm/smp_scu.h>
+#include <asm/smp.h>
+#include "addr-map.h"
+
+#define SW_BRANCH_VIRT_ADDR	CIU_REG(0x24)
+
+static int mmp3_boot_secondary(unsigned int cpu, struct task_struct *idle)
+{
+	/*
+	 * Apparently, the boot ROM on the second core spins on this
+	 * register becoming non-zero and then jumps to the address written
+	 * there. No IPIs involved.
+	 */
+	__raw_writel(__pa_symbol(secondary_startup), SW_BRANCH_VIRT_ADDR);
+	return 0;
+}
+
+static void mmp3_smp_prepare_cpus(unsigned int max_cpus)
+{
+	scu_enable(SCU_VIRT_BASE);
+}
+
+static const struct smp_operations mmp3_smp_ops __initconst = {
+	.smp_prepare_cpus	= mmp3_smp_prepare_cpus,
+	.smp_boot_secondary	= mmp3_boot_secondary,
+};
+CPU_METHOD_OF_DECLARE(mmp3_smp, "marvell,mmp3-smp", &mmp3_smp_ops);