diff mbox

[v2,05/19] OMAP4: PM: Add CPUX OFF mode support

Message ID 1299766095-23879-6-git-send-email-santosh.shilimkar@ti.com (mailing list archive)
State New, archived
Delegated to: Kevin Hilman
Headers show

Commit Message

Santosh Shilimkar March 10, 2011, 2:08 p.m. UTC
None
diff mbox

Patch

diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index 1bf9cd2..04b97bb 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -63,13 +63,15 @@  obj-$(CONFIG_ARCH_OMAP2)		+= pm24xx.o
 obj-$(CONFIG_ARCH_OMAP2)		+= sleep24xx.o pm_bus.o
 obj-$(CONFIG_ARCH_OMAP3)		+= pm34xx.o sleep34xx.o \
 					   cpuidle34xx.o pm_bus.o
-obj-$(CONFIG_ARCH_OMAP4)		+= pm44xx.o pm_bus.o
+obj-$(CONFIG_ARCH_OMAP4)		+= pm44xx.o pm_bus.o \
+					   omap4-mpuss-lowpower.o sleep44xx.o
 obj-$(CONFIG_PM_DEBUG)			+= pm-debug.o
 obj-$(CONFIG_OMAP_SMARTREFLEX)          += sr_device.o smartreflex.o
 obj-$(CONFIG_OMAP_SMARTREFLEX_CLASS3)	+= smartreflex-class3.o
 
 AFLAGS_sleep24xx.o			:=-Wa,-march=armv6
 AFLAGS_sleep34xx.o			:=-Wa,-march=armv7-a
+AFLAGS_sleep44xx.o			:=-Wa,-march=armv7-a
 
 ifeq ($(CONFIG_PM_VERBOSE),y)
 CFLAGS_pm_bus.o				+= -DDEBUG
diff --git a/arch/arm/mach-omap2/include/mach/omap4-common.h b/arch/arm/mach-omap2/include/mach/omap4-common.h
index 284180c..a6ce905 100644
--- a/arch/arm/mach-omap2/include/mach/omap4-common.h
+++ b/arch/arm/mach-omap2/include/mach/omap4-common.h
@@ -13,6 +13,9 @@ 
 #ifndef OMAP_ARCH_OMAP4_COMMON_H
 #define OMAP_ARCH_OMAP4_COMMON_H
 
+#include <asm/proc-fns.h>
+
+#ifndef __ASSEMBLER__
 /*
  * wfi used in low power code. Directly opcode is used instead
  * of instruction to avoid mulit-omap build break
@@ -43,4 +46,47 @@  extern void __iomem *omap4_get_sar_ram_base(void);
 extern void __init gic_init_irq(void);
 extern void omap_smc1(u32 fn, u32 arg);
 
+/*
+ * Read MPIDR: Multiprocessor affinity register
+ */
+static inline unsigned int hard_smp_processor_id(void)
+{
+	unsigned int cpunum;
+
+	asm volatile (
+	"mrc	 p15, 0, %0, c0, c0, 5\n"
+		: "=r" (cpunum));
+	return cpunum &= 0x0f;
+}
+
+#if defined(CONFIG_SMP)	&& defined(CONFIG_PM)
+extern int omap4_mpuss_init(void);
+extern int omap4_enter_lowpower(unsigned int cpu, unsigned int power_state);
+extern void omap4_cpu_suspend(unsigned int cpu, unsigned int save_state);
+extern void omap4_cpu_resume(void);
+
+#else
+
+static inline int omap4_enter_lowpower(unsigned int cpu,
+					unsigned int power_state)
+{
+	cpu_do_idle();
+	return 0;
+}
+
+static inline int omap4_mpuss_init(void)
+{
+	return 0;
+}
+
+static inline void omap4_cpu_suspend(unsigned int cpu, unsigned int save_state)
+{
+}
+
+static inline void omap4_cpu_resume(void)
+{
+}
+
 #endif
+#endif /* __ASSEMBLER__ */
+#endif /* OMAP_ARCH_OMAP4_COMMON_H */
diff --git a/arch/arm/mach-omap2/omap4-mpuss-lowpower.c b/arch/arm/mach-omap2/omap4-mpuss-lowpower.c
new file mode 100644
index 0000000..21c5ad3
--- /dev/null
+++ b/arch/arm/mach-omap2/omap4-mpuss-lowpower.c
@@ -0,0 +1,240 @@ 
+/*
+ * OMAP4 MPUSS low power code
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Written by Santosh Shilimkar <santosh.shilimkar@ti.com>
+ *
+ * OMAP4430 MPUSS mainly consists of dual Cortex-A9 with per-CPU
+ * Local timer and Watchdog, GIC, SCU, PL310 L2 cache controller,
+ * CPU0 and CPU1 LPRM modules.
+ * CPU0, CPU1 and MPUSS each have there own power domain and
+ * hence multiple low power combinations of MPUSS are possible.
+ *
+ * The CPU0 and CPU1 can't support Closed switch Retention (CSWR)
+ * because the mode is not supported by hw constraints of dormant
+ * mode. While waking up from the dormant mode, a reset  signal
+ * to the Cortex-A9 processor must be asserted by the external
+ * power controller.
+ *
+ * With architectural inputs and hardware recommendations, only
+ * below modes are supported from power gain vs latency point of view.
+ *
+ *	CPU0		CPU1		MPUSS
+ *	----------------------------------------------
+ *	ON		ON		ON
+ *	ON(Inactive)	OFF		ON(Inactive)
+ *	OFF		OFF		CSWR
+ *	OFF		OFF		OSWR (*TBD)
+ *	OFF		OFF		OFF* (*TBD)
+ *	----------------------------------------------
+ *
+ * Note: CPU0 is the master core and it is the last CPU to go down
+ * and first to wake-up when MPUSS low power states are excercised
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/errno.h>
+#include <linux/linkage.h>
+#include <linux/smp.h>
+
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <asm/smp_scu.h>
+#include <asm/system.h>
+
+#include <plat/omap44xx.h>
+#include <mach/omap4-common.h>
+
+#include "omap4-sar-layout.h"
+#include "pm.h"
+#include "powerdomain.h"
+
+#ifdef CONFIG_SMP
+
+struct omap4_cpu_pm_info {
+	struct powerdomain *pwrdm;
+	void __iomem *scu_sar_addr;
+};
+
+static DEFINE_PER_CPU(struct omap4_cpu_pm_info, omap4_pm_info);
+
+/*
+ * Set the CPUx powerdomain's previous power state
+ */
+static inline void set_cpu_next_pwrst(unsigned int cpu_id,
+				unsigned int power_state)
+{
+	struct omap4_cpu_pm_info *pm_info = &per_cpu(omap4_pm_info, cpu_id);
+
+	pwrdm_set_next_pwrst(pm_info->pwrdm, power_state);
+}
+
+/*
+ * Read CPU's previous power state
+ */
+static inline unsigned int read_cpu_prev_pwrst(unsigned int cpu_id)
+{
+	struct omap4_cpu_pm_info *pm_info = &per_cpu(omap4_pm_info, cpu_id);
+
+	return pwrdm_read_prev_pwrst(pm_info->pwrdm);
+}
+
+/*
+ * Clear the CPUx powerdomain's previous power state
+ */
+static inline void clear_cpu_prev_pwrst(unsigned int cpu_id)
+{
+	struct omap4_cpu_pm_info *pm_info = &per_cpu(omap4_pm_info, cpu_id);
+
+	pwrdm_clear_all_prev_pwrst(pm_info->pwrdm);
+}
+
+/*
+ * Store the SCU power status value to scratchpad memory
+ */
+static void scu_pwrst_prepare(unsigned int cpu_id, unsigned int cpu_state)
+{
+	struct omap4_cpu_pm_info *pm_info = &per_cpu(omap4_pm_info, cpu_id);
+	u32 scu_pwr_st;
+
+	switch (cpu_state) {
+	case PWRDM_POWER_RET:
+		scu_pwr_st = SCU_PM_DORMANT;
+		break;
+	case PWRDM_POWER_OFF:
+		scu_pwr_st = SCU_PM_POWEROFF;
+		break;
+	case PWRDM_POWER_ON:
+	case PWRDM_POWER_INACTIVE:
+	default:
+		scu_pwr_st = SCU_PM_NORMAL;
+		break;
+	}
+
+	__raw_writel(scu_pwr_st, pm_info->scu_sar_addr);
+}
+
+/*
+ * OMAP4 MPUSS Low Power Entry Function
+ *
+ * The purpose of this function is to manage low power programming
+ * of OMAP4 MPUSS subsystem
+ * Paramenters:
+ *	cpu : CPU ID
+ *	power_state: Targetted Low power state.
+ */
+int omap4_enter_lowpower(unsigned int cpu, unsigned int power_state)
+{
+	unsigned int save_state = 0;
+	unsigned int wakeup_cpu = hard_smp_processor_id();
+
+	if ((cpu >= NR_CPUS) || (omap_rev() == OMAP4430_REV_ES1_0))
+		goto ret;
+
+	switch (power_state) {
+	case PWRDM_POWER_ON:
+	case PWRDM_POWER_INACTIVE:
+		save_state = 0;
+		break;
+	case PWRDM_POWER_OFF:
+		save_state = 1;
+		break;
+	case PWRDM_POWER_RET:
+	default:
+		/*
+		 * CPUx CSWR is invalid hardware state. Also CPUx OSWR
+		 * doesn't make much scense, since logic is lost and $L1
+		 * needs to be cleaned because of coherency. This makes
+		 * CPUx OSWR equivalent to CPUX OFF and hence not supported
+		 */
+		WARN_ON(1);
+		goto ret;
+	}
+
+	clear_cpu_prev_pwrst(cpu);
+	set_cpu_next_pwrst(cpu, power_state);
+	scu_pwrst_prepare(cpu, power_state);
+
+	/*
+	 * Call low level function  with targeted CPU id
+	 * and its low power state.
+	 */
+	omap4_cpu_suspend(cpu, save_state);
+
+	/*
+	 * Restore the CPUx power state to ON otherwise CPUx
+	 * power domain can transitions to programmed low power
+	 * state while doing WFI outside the low powe code. On
+	 * secure devices, CPUx does WFI which can result in
+	 * domain transition
+	 */
+	wakeup_cpu = hard_smp_processor_id();
+	set_cpu_next_pwrst(wakeup_cpu, PWRDM_POWER_ON);
+
+ret:
+	return 0;
+}
+
+/*
+ * Initialise OMAP4 MPUSS
+ */
+int __init omap4_mpuss_init(void)
+{
+	struct omap4_cpu_pm_info *pm_info;
+	void __iomem *sar_ram_base = omap4_get_sar_ram_base();
+
+	if (omap_rev() == OMAP4430_REV_ES1_0) {
+		WARN(1, "Power Management not supported on OMAP4430 ES1.0\n");
+		return -ENODEV;
+	}
+
+	/* Initilaise per CPU PM information */
+	pm_info = &per_cpu(omap4_pm_info, 0x0);
+	pm_info->scu_sar_addr = sar_ram_base + SCU_OFFSET0;
+	pm_info->pwrdm = pwrdm_lookup("cpu0_pwrdm");
+	if (!pm_info->pwrdm) {
+		pr_err("Lookup failed for CPU0 pwrdm\n");
+		return -ENODEV;
+	}
+
+	/* Clear CPU previous power domain state */
+	pwrdm_clear_all_prev_pwrst(pm_info->pwrdm);
+
+	/* Initialise CPU0 power domain state to ON */
+	pwrdm_set_next_pwrst(pm_info->pwrdm, PWRDM_POWER_ON);
+
+	pm_info = &per_cpu(omap4_pm_info, 0x1);
+	pm_info->scu_sar_addr = sar_ram_base + SCU_OFFSET1;
+	pm_info->pwrdm = pwrdm_lookup("cpu1_pwrdm");
+	if (!pm_info->pwrdm) {
+		pr_err("Lookup failed for CPU1 pwrdm\n");
+		return -ENODEV;
+	}
+
+	/* Clear CPU previous power domain state */
+	pwrdm_clear_all_prev_pwrst(pm_info->pwrdm);
+
+	/* Initialise CPU1 power domain state to ON */
+	pwrdm_set_next_pwrst(pm_info->pwrdm, PWRDM_POWER_ON);
+
+	/*
+	 * Program the wakeup routine address for the CPU0 and CPU1
+	 * used for OFF or DORMANT wakeup. Wakeup routine address
+	 * is fixed so programit in init itself.
+	 */
+	__raw_writel(virt_to_phys(omap4_cpu_resume),
+			sar_ram_base + CPU1_WAKEUP_NS_PA_ADDR_OFFSET);
+	__raw_writel(virt_to_phys(omap4_cpu_resume),
+			sar_ram_base + CPU0_WAKEUP_NS_PA_ADDR_OFFSET);
+
+	return 0;
+}
+
+#endif
+
diff --git a/arch/arm/mach-omap2/omap4-sar-layout.h b/arch/arm/mach-omap2/omap4-sar-layout.h
index 1cfb4dd..8b71b1e 100644
--- a/arch/arm/mach-omap2/omap4-sar-layout.h
+++ b/arch/arm/mach-omap2/omap4-sar-layout.h
@@ -19,4 +19,15 @@ 
 #define SAR_BANK3_OFFSET		0x2000
 #define SAR_BANK4_OFFSET		0x3000
 
+/* Scratch pad memory offsets from SAR_BANK1 */
+#define CPU0_SAVE_OFFSET			0xb00
+#define CPU1_SAVE_OFFSET			0xc00
+#define MMU_OFFSET				0xd00
+#define SCU_OFFSET0				0xd20
+#define SCU_OFFSET1				0xd24
+
+/* CPUx Wakeup Non-Secure Physical Address offsets in SAR_BANK3 */
+#define CPU0_WAKEUP_NS_PA_ADDR_OFFSET		0xa04
+#define CPU1_WAKEUP_NS_PA_ADDR_OFFSET		0xa08
+
 #endif
diff --git a/arch/arm/mach-omap2/pm44xx.c b/arch/arm/mach-omap2/pm44xx.c
index 76cfff2..7502723 100644
--- a/arch/arm/mach-omap2/pm44xx.c
+++ b/arch/arm/mach-omap2/pm44xx.c
@@ -111,6 +111,12 @@  static int __init omap4_pm_init(void)
 		pr_err("Failed to setup powerdomains\n");
 		goto err2;
 	}
+
+	ret = omap4_mpuss_init();
+	if (ret) {
+		pr_err("Failed to initialise OMAP4 MPUSS\n");
+		goto err2;
+	}
 #endif
 
 #ifdef CONFIG_SUSPEND
diff --git a/arch/arm/mach-omap2/sleep44xx.S b/arch/arm/mach-omap2/sleep44xx.S
new file mode 100644
index 0000000..1d166ef
--- /dev/null
+++ b/arch/arm/mach-omap2/sleep44xx.S
@@ -0,0 +1,335 @@ 
+/*
+ * OMAP44xx CPU low power powerdown and powerup code.
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Written by Santosh Shilimkar <santosh.shilimkar@ti.com>
+ *
+ * This program is free software,you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/linkage.h>
+#include <asm/system.h>
+#include <asm/smp_scu.h>
+#include <asm/memory.h>
+
+#include <plat/omap44xx.h>
+#include <mach/omap4-common.h>
+#include <asm/hardware/cache-l2x0.h>
+
+#include "omap4-sar-layout.h"
+
+#ifdef CONFIG_SMP
+
+/* Masks used for MMU manipulation */
+#define TTRBIT_MASK				0xffffc000
+#define TABLE_INDEX_MASK			0xfff00000
+#define TABLE_ENTRY				0x00000c02
+#define CACHE_DISABLE_MASK			0xffffe7fb
+#define TABLE_ADDRESS_OFFSET			0x04
+#define CR_VALUE_OFFSET				0x08
+
+/*
+ * =============================
+ * == CPU suspend entry point ==
+ * =============================
+ *
+ * void omap4_cpu_suspend(unsigned int cpu, unsigned int save_state)
+ *
+ * This function code saves the CPU context and performs the CPU
+ * power down sequence. Calling WFI effectively changes the CPU
+ * power domains states to the desired target power state.
+ *
+ * @cpu : contains cpu id (r0)
+ * @save_state : contains context save state (r1)
+ *	0 - No context lost
+ * 	1 - CPUx L1 and logic lost: MPUSS CSWR
+ * 	2 - CPUx L1 and logic lost + GIC lost: MPUSS OSWR
+ *	3 - CPUx L1 and logic lost + GIC + L2 lost: MPUSS OFF
+ * @return: This function never returns for CPU OFF and DORMANT power states.
+ * Post WFI, CPU transitions to DORMANT or OFF power state and on wake-up
+ * from this follows a full CPU reset path via ROM code to CPU restore code.
+ * It returns to the caller for CPU INACTIVE and ON power states or in case
+ * CPU failed to transition to targeted OFF/DORMANT state.
+ */
+
+ENTRY(omap4_cpu_suspend)
+	stmfd	sp!, {r0-r12, lr}		@ Save registers on stack
+	cmp	r1, #0x0
+	beq	do_WFI				@ Nothing to save, jump to WFI
+	mov	r5, r0
+	bl	omap4_get_sar_ram_base
+	mov	r8, r0
+	ands	r5, r5, #0x0f
+	orreq	r8, r8, #CPU0_SAVE_OFFSET
+	orrne	r8, r8, #CPU1_SAVE_OFFSET
+
+	/*
+	 * Save only needed CPU CP15 registers. VFP, breakpoint,
+	 * performance monitor registers are not saved. Generic
+	 * code suppose to take care of those.
+	 */
+	mov	r4, sp				@ Store sp
+	mrs	r5, spsr			@ Store spsr
+	mov	r6, lr				@ Store lr
+	stmia	r8!, {r4-r6}
+
+	/* c1 and c2 registers */
+	mrc	p15, 0, r4, c1, c0, 2		@ CPACR
+	mrc	p15, 0, r5, c2, c0, 0		@ TTBR0
+	mrc	p15, 0, r6, c2, c0, 1		@ TTBR1
+	mrc	p15, 0, r7, c2, c0, 2		@ TTBCR
+	stmia	r8!, {r4-r7}
+
+	/* c3 and c10 registers */
+	mrc	p15, 0, r4, c3, c0, 0		@ DACR
+	mrc	p15, 0, r5, c10, c2, 0		@ PRRR
+	mrc	p15, 0, r6, c10, c2, 1		@ NMRR
+	stmia	r8!,{r4-r6}
+
+	/* c12, c13 and CPSR registers */
+	mrc	p15, 0, r4, c13, c0, 1		@ Context ID
+	mrc	p15, 0, r5, c13, c0, 2		@ User r/w thread ID
+	mrc	p15, 0, r6, c12, c0, 0		@ Secure or NS VBAR
+	mrs	r7, cpsr			@ Store CPSR
+	stmia	r8!, {r4-r7}
+
+	/* c1 control register */
+	mrc	p15, 0, r4, c1, c0, 0		@ Save control register
+	stmia	r8!, {r4}
+
+	/*
+	 * Flush all data from the L1 data cache before disabling
+	 * SCTLR.C bit.
+	 */
+	bl	v7_flush_dcache_all
+
+	/*
+	 * Clear the SCTLR.C bit to prevent further data cache
+	 * allocation. Clearing SCTLR.C would make all the data accesses
+	 * strongly ordered and would not hit the cache.
+	 */
+	mrc	p15, 0, r0, c1, c0, 0
+	bic	r0, r0, #(1 << 2)		@ Disable the C bit
+	mcr	p15, 0, r0, c1, c0, 0
+	isb
+
+	/*
+	 * Invalidate L1 data cache. Even though only invalidate is
+	 * necessary exported flush API is used here. Doing clean
+	 * on already clean cache would be almost NOP.
+	 */
+	bl	v7_flush_dcache_all
+
+	/*
+	 * Switch the CPU from Symmetric Multiprocessing (SMP) mode
+	 * to AsymmetricMultiprocessing (AMP) mode by programming
+	 * the SCU power status to DORMANT or OFF mode.
+	 * This enables the CPU to be taken out of coherency by
+	 * preventing the CPU from receiving cache, TLB, or BTB
+	 * maintenance operations broadcast by other CPUs in the cluster.
+	 */
+	bl	omap4_get_sar_ram_base
+	mov	r8, r0
+	mrc	p15, 0, r0, c0, c0, 5		@ Read MPIDR
+	ands	r0, r0, #0x0f
+	ldreq	r1, [r8, #SCU_OFFSET0]
+	ldrne	r1, [r8, #SCU_OFFSET1]
+	bl	omap4_get_scu_base
+	bl     scu_power_mode
+
+do_WFI:
+	/*
+	 * Execute an ISB instruction to ensure that all of the
+	 * CP15 register changes have been committed.
+	 */
+	isb
+
+	/*
+	 * Execute a barrier instruction to ensure that all cache,
+	 * TLB and branch predictor maintenance operations issued
+	 * by any CPU in the cluster have completed.
+	 */
+	dsb
+	dmb
+
+	/*
+	 * Execute a WFI instruction and wait until the
+	 * STANDBYWFI output is asserted to indicate that the
+	 * CPU is in idle and low power state.
+	 */
+	wfi					@ Wait For Interrupt
+
+	/*
+	 * CPU is here when it failed to enter OFF/DORMANT or
+	 * no low power state was attempted.
+	 */
+	mrc	p15, 0, r0, c1, c0, 0
+	tst	r0, #(1 << 2)			@ Check C bit enabled?
+	orreq	r0, r0, #(1 << 2)		@ Enable the C bit
+	mcreq	p15, 0, r0, c1, c0, 0
+	isb
+
+	/*
+	 * Ensure the CPU power state is set to NORMAL in
+	 * SCU power state so that CPU is back in coherency.
+	 * In non-coherent mode CPU can lock-up and lead to
+	 * system deadlock.
+	 */
+	bl	omap4_get_scu_base
+	mov	r1, #SCU_PM_NORMAL
+	bl     scu_power_mode
+	isb
+	dsb
+
+	ldmfd	sp!, {r0-r12, pc}		@ Restore regs and return
+ENDPROC(omap4_cpu_suspend)
+
+/*
+ * ============================
+ * == CPU resume entry point ==
+ * ============================
+ *
+ * void omap4_cpu_resume(void)
+ *
+ * ROM code jumps to this function while waking up from CPU
+ * OFF or DORMANT state. Physical address of the function is
+ * stored in the SAR RAM while entering to OFF or DORMANT mode.
+ */
+
+ENTRY(omap4_cpu_resume)
+	/*
+	 * Check the wakeup cpuid and use appropriate
+	 * SAR BANK location for context restore.
+	 */
+	ldr	r3, =OMAP44XX_SAR_RAM_BASE
+	mov	r1, #0
+	mcr	p15, 0, r1, c7, c5, 0		@ Invalidate L1 I
+	mrc	p15, 0, r0, c0, c0, 5		@ MPIDR
+	ands	r0, r0, #0x0f
+	orreq	r3, r3, #CPU0_SAVE_OFFSET
+	orrne	r3, r3, #CPU1_SAVE_OFFSET
+
+	/* Restore cp15 registers */
+	ldmia	r3!, {r4-r6}
+	mov	sp, r4				@ Restore sp
+	msr	spsr_cxsf, r5			@ Restore spsr
+	mov	lr, r6				@ Restore lr
+
+	/* c1 and c2 registers */
+	ldmia	r3!, {r4-r7}
+	mcr	p15, 0, r4, c1, c0, 2		@ CPACR
+	mcr	p15, 0, r5, c2, c0, 0		@ TTBR0
+	mcr	p15, 0, r6, c2, c0, 1		@ TTBR1
+	mcr	p15, 0, r7, c2, c0, 2		@ TTBCR
+
+	/* c3 and c10 registers */
+	ldmia	r3!,{r4-r6}
+	mcr	p15, 0, r4, c3, c0, 0		@ DACR
+	mcr	p15, 0, r5, c10, c2, 0		@ PRRR
+	mcr	p15, 0, r6, c10, c2, 1		@ NMRR
+
+	/* c12, c13 and CPSR registers */
+	ldmia	r3!,{r4-r7}
+	mcr	p15, 0, r4, c13, c0, 1		@ Context ID
+	mcr	p15, 0, r5, c13, c0, 2		@ User r/w thread ID
+	mrc	p15, 0, r6, c12, c0, 0		@ Secure or NS VBAR
+	msr	cpsr, r7			@ store cpsr
+
+	/*
+	 * Enabling MMU here. Page entry needs to be altered
+	 * to create temporary 1:1 map and then resore the entry
+	 * ones MMU is enabled
+	 */
+	mrc	p15, 0, r7, c2, c0, 2		@ Read TTBRControl
+	and	r7, #0x7			@ Extract N (0:2) to decide
+	cmp	r7, #0x0			@ TTBR0/TTBR1
+	beq	use_ttbr0
+ttbr_error:
+	b	ttbr_error			@ Only N = 0 supported
+use_ttbr0:
+	mrc	p15, 0, r2, c2, c0, 0		@ Read TTBR0
+	ldr	r5, =TTRBIT_MASK
+	and	r2, r5
+	mov	r4, pc
+	ldr	r5, =TABLE_INDEX_MASK
+	and	r4, r5				@ r4 = 31 to 20 bits of pc
+	ldr	r1, =TABLE_ENTRY
+	add	r1, r1, r4			@ r1 has value of table entry
+	lsr	r4, #18				@ Address of table entry
+	add	r2, r4				@ r2 - location to be modified
+
+	/* Ensure the modified entry makes it to main memory */
+#ifdef CONFIG_CACHE_L2X0
+	ldr	r5, =OMAP44XX_L2CACHE_BASE
+	str	r2, [r5, #L2X0_CLEAN_INV_LINE_PA]
+wait_l2:
+	ldr	r0, [r5, #L2X0_CLEAN_INV_LINE_PA]
+	ands	r0, #1
+	bne	wait_l2
+#endif
+
+	/* Storing previous entry of location being modified */
+	ldr     r5, =OMAP44XX_SAR_RAM_BASE
+	ldr	r4, [r2]
+	str	r4, [r5, #MMU_OFFSET]		@ Modify the table entry
+	str	r1, [r2]
+
+	/*
+	 * Storing address of entry being modified
+	 * It will be restored after enabling MMU
+	 */
+	ldr     r5, =OMAP44XX_SAR_RAM_BASE
+	orr	r5, r5, #MMU_OFFSET
+	str	r2, [r5, #TABLE_ADDRESS_OFFSET]
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c5, 4		@ Flush prefetch buffer
+	mcr	p15, 0, r0, c7, c5, 6		@ Invalidate BTB
+	mcr	p15, 0, r0, c8, c5, 0		@ Invalidate ITLB
+	mcr	p15, 0, r0, c8, c6, 0		@ Invalidate DTLB
+
+	/*
+	 * Restore control register  but don't enable Data caches here.
+	 * Caches will be enabled after restoring MMU table entry.
+	 */
+	ldmia	r3!, {r4}
+	str	r4, [r5, #CR_VALUE_OFFSET]	@ Store previous value of CR
+	ldr	r2, =CACHE_DISABLE_MASK
+	and	r4, r2
+	mcr	p15, 0, r4, c1, c0, 0
+	isb
+	dsb
+	ldr	r0, =mmu_on_label
+	bx	r0
+mmu_on_label:
+	/* Set up the per-CPU stacks */
+	bl	cpu_init
+
+	/*
+	 * Restore the MMU table entry that was modified for
+	 * enabling MMU.
+	 */
+	bl	omap4_get_sar_ram_base
+	mov	r8, r0
+	orr	r8, r8, #MMU_OFFSET		@ Get address of entry that..
+	ldr	r2, [r8, #TABLE_ADDRESS_OFFSET]	@ was modified
+	ldr	r3, =local_va2pa_offet
+	add	r2, r2, r3
+	ldr	r0, [r8]			@ Get the previous value..
+	str	r0, [r2]			@ which needs to be restored
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c1, 6		@ flush TLB and issue barriers
+	dsb
+	isb
+	ldr	r0, [r8, #CR_VALUE_OFFSET]	@ Restore the Control register
+	mcr     p15, 0, r0, c1, c0, 0		@ with caches enabled.
+	isb
+
+	ldmfd	sp!, {r0-r12, pc}		@ restore regs and return
+
+	.equ	local_va2pa_offet, (PHYS_OFFSET + PAGE_OFFSET)
+
+ENDPROC(omap4_cpu_resume)
+
+#endif