ARM: tegra20: add CPU hotplug support

Hotplug function put CPU in offline or online mode at runtime.
When the CPU been put into offline, it was been clock gated. The
offline CPU can be power gated, when the remaining CPU goes into
LP2.

Based on the worked by:
Colin Cross <ccross@android.com>
Gary King <gking@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/mach-tegra/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_CPU_IDLE)			+= sleep.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)         += tegra20_clocks.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)         += tegra20_clocks_data.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)		+= tegra2_emc.o
+obj-$(CONFIG_ARCH_TEGRA_2x_SOC)		+= sleep-t20.o
 obj-$(CONFIG_ARCH_TEGRA_3x_SOC)		+= tegra30_clocks.o
 obj-$(CONFIG_ARCH_TEGRA_3x_SOC)		+= tegra30_clocks_data.o
 obj-$(CONFIG_ARCH_TEGRA_3x_SOC)		+= sleep-t30.o

arch/arm/mach-tegra/common.c

@@ -136,6 +136,7 @@ void __init tegra20_init_early(void)
 	tegra_init_cache(0x331, 0x441);
 	tegra_pmc_init();
 	tegra_powergate_init();
+	tegra20_hotplug_init();
 }
 #endif
 #ifdef CONFIG_ARCH_TEGRA_3x_SOC

arch/arm/mach-tegra/hotplug.c

@@ -56,6 +56,14 @@ int platform_cpu_disable(unsigned int cpu)
 	return cpu == 0 ? -EPERM : 0;
 }
 
+#ifdef CONFIG_ARCH_TEGRA_2x_SOC
+extern void tegra20_hotplug_shutdown(void);
+void __init tegra20_hotplug_init(void)
+{
+	tegra_hotplug_shutdown = tegra20_hotplug_shutdown;
+}
+#endif
+
 #ifdef CONFIG_ARCH_TEGRA_3x_SOC
 extern void tegra30_hotplug_shutdown(void);
 void __init tegra30_hotplug_init(void)

arch/arm/mach-tegra/sleep-t20.S

+/*
+ * Copyright (c) 2010-2012, NVIDIA Corporation. All rights reserved.
+ * Copyright (c) 2011, Google, Inc.
+ *
+ * Author: Colin Cross <ccross@android.com>
+ *         Gary King <gking@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/assembler.h>
+
+#include <mach/iomap.h>
+
+#include "sleep.h"
+#include "flowctrl.h"
+
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PM_SLEEP)
+/*
+ * tegra20_hotplug_shutdown(void)
+ *
+ * puts the current cpu in reset
+ * should never return
+ */
+ENTRY(tegra20_hotplug_shutdown)
+	/* Turn off SMP coherency */
+	exit_smp r4, r5
+
+	/* Put this CPU down */
+	cpu_id	r0
+	bl	tegra20_cpu_shutdown
+	mov	pc, lr			@ should never get here
+ENDPROC(tegra20_hotplug_shutdown)
+
+/*
+ * tegra20_cpu_shutdown(int cpu)
+ *
+ * r0 is cpu to reset
+ *
+ * puts the specified CPU in wait-for-event mode on the flow controller
+ * and puts the CPU in reset
+ * can be called on the current cpu or another cpu
+ * if called on the current cpu, does not return
+ * MUST NOT BE CALLED FOR CPU 0.
+ *
+ * corrupts r0-r3, r12
+ */
+ENTRY(tegra20_cpu_shutdown)
+	cmp	r0, #0
+	moveq	pc, lr			@ must not be called for CPU 0
+
+	cpu_to_halt_reg r1, r0
+	ldr	r3, =TEGRA_FLOW_CTRL_VIRT
+	mov	r2, #FLOW_CTRL_WAITEVENT | FLOW_CTRL_JTAG_RESUME
+	str	r2, [r3, r1]		@ put flow controller in wait event mode
+	ldr	r2, [r3, r1]
+	isb
+	dsb
+	movw	r1, 0x1011
+	mov	r1, r1, lsl r0
+	ldr	r3, =TEGRA_CLK_RESET_VIRT
+	str	r1, [r3, #0x340]	@ put slave CPU in reset
+	isb
+	dsb
+	cpu_id	r3
+	cmp	r3, r0
+	beq	.
+	mov	pc, lr
+ENDPROC(tegra20_cpu_shutdown)
+#endif

arch/arm/mach-tegra/sleep.h

@@ -23,6 +23,8 @@
 					+ IO_CPU_VIRT)
 #define TEGRA_FLOW_CTRL_VIRT (TEGRA_FLOW_CTRL_BASE - IO_PPSB_PHYS \
 					+ IO_PPSB_VIRT)
+#define TEGRA_CLK_RESET_VIRT (TEGRA_CLK_RESET_BASE - IO_PPSB_PHYS \
+					+ IO_PPSB_VIRT)
 
 #ifdef __ASSEMBLY__
 /* returns the offset of the flow controller halt register for a cpu */
@@ -72,8 +74,10 @@
 #else
 
 #ifdef CONFIG_HOTPLUG_CPU
+void tegra20_hotplug_init(void);
 void tegra30_hotplug_init(void);
 #else
+static inline void tegra20_hotplug_init(void) {}
 static inline void tegra30_hotplug_init(void) {}
 #endif