ARM: imx: add suspend in ocram support for i.mx6q

When system enter suspend, we can set the DDR IO to
high-Z state to save DDR IOs' power consumption, this
operation can save many power(from ~26mA@1.5V to ~15mA@1.5V,
measured on i.MX6Q SabreSD board, R25) of DDR IOs. To
achieve that, we need to copy the suspend code to ocram
and run the low level hardware related code(set DDR IOs
to high-Z state) in ocram.

If there is no ocram space available, then system will
still do suspend in external DDR, hence no DDR IOs will
be set to high-Z.

The OCRAM usage layout is as below,

ocram suspend region(4K currently):
======================== high address ======================
                              .
                              .
                              .
                              ^
                              ^
                              ^
                      imx6_suspend code
             PM_INFO structure(imx6_cpu_pm_info)
======================== low address =======================

Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

7 files changed, 577 insertions, 11 deletions

diff --git a/arch/arm/mach-imx/Makefile b/arch/arm/mach-imx/Makefile
index 21114a9a2ae7..48b47aa6224a 100644
--- a/arch/arm/mach-imx/Makefile
+++ b/arch/arm/mach-imx/Makefile
@@ -102,7 +102,8 @@ obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o
 obj-$(CONFIG_SOC_IMX6Q) += clk-imx6q.o mach-imx6q.o
 obj-$(CONFIG_SOC_IMX6SL) += clk-imx6sl.o mach-imx6sl.o
 
-obj-$(CONFIG_SOC_IMX6Q) += pm-imx6q.o headsmp.o
+AFLAGS_suspend-imx6.o :=-Wa,-march=armv7-a
+obj-$(CONFIG_SOC_IMX6Q) += pm-imx6q.o headsmp.o suspend-imx6.o
 # i.MX6SL reuses i.MX6Q code
 obj-$(CONFIG_SOC_IMX6SL) += pm-imx6q.o headsmp.o
 
diff --git a/arch/arm/mach-imx/common.h b/arch/arm/mach-imx/common.h
index b909b689619b..91d69ccf7c76 100644
--- a/arch/arm/mach-imx/common.h
+++ b/arch/arm/mach-imx/common.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2013 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2004-2014 Freescale Semiconductor, Inc. All Rights Reserved.
  */
 
 /*
@@ -145,8 +145,12 @@ void imx6sl_set_wait_clk(bool enter);
 void imx_cpu_die(unsigned int cpu);
 int imx_cpu_kill(unsigned int cpu);
 
+void imx6_suspend(void __iomem *ocram_vbase);
 void imx6q_pm_init(void);
+void imx6dl_pm_init(void);
+void imx6sl_pm_init(void);
 void imx6q_pm_set_ccm_base(void __iomem *base);
+
 #ifdef CONFIG_PM
 void imx5_pm_init(void);
 #else
diff --git a/arch/arm/mach-imx/hardware.h b/arch/arm/mach-imx/hardware.h
index a3b0b04b45c9..abf43bb47eca 100644
--- a/arch/arm/mach-imx/hardware.h
+++ b/arch/arm/mach-imx/hardware.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2007 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2004-2007, 2014 Freescale Semiconductor, Inc. All Rights Reserved.
  * Copyright 2008 Juergen Beisert, kernel@pengutronix.de
  *
  * This program is free software; you can redistribute it and/or
@@ -20,7 +20,9 @@
 #ifndef __ASM_ARCH_MXC_HARDWARE_H__
 #define __ASM_ARCH_MXC_HARDWARE_H__
 
+#ifndef __ASSEMBLY__
 #include <asm/io.h>
+#endif
 #include <asm/sizes.h>
 
 #define addr_in_module(addr, mod) \
diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
index 76e5db4fce35..f9cbbf9e5e31 100644
--- a/arch/arm/mach-imx/mach-imx6q.c
+++ b/arch/arm/mach-imx/mach-imx6q.c
@@ -212,7 +212,7 @@ static void __init imx6q_init_machine(void)
         of_platform_populate(NULL, of_default_bus_match_table, NULL, parent);
 
         imx_anatop_init();
-        imx6q_pm_init();
+        cpu_is_imx6q() ?  imx6q_pm_init() : imx6dl_pm_init();
         imx6q_1588_init();
 }
 
diff --git a/arch/arm/mach-imx/mach-imx6sl.c b/arch/arm/mach-imx/mach-imx6sl.c
index a26fdb2b1a6f..ad323385115c 100644
--- a/arch/arm/mach-imx/mach-imx6sl.c
+++ b/arch/arm/mach-imx/mach-imx6sl.c
@@ -58,8 +58,7 @@ static void __init imx6sl_init_machine(void)
 
         imx6sl_fec_init();
         imx_anatop_init();
-        /* Reuse imx6q pm code */
-        imx6q_pm_init();
+        imx6sl_pm_init();
 }
 
 static void __init imx6sl_init_irq(void)
diff --git a/arch/arm/mach-imx/pm-imx6q.c b/arch/arm/mach-imx/pm-imx6q.c
index 30af3c0e1bf3..a7b1e58a3ac1 100644
--- a/arch/arm/mach-imx/pm-imx6q.c
+++ b/arch/arm/mach-imx/pm-imx6q.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2013 Freescale Semiconductor, Inc.
+ * Copyright 2011-2014 Freescale Semiconductor, Inc.
  * Copyright 2011 Linaro Ltd.
  *
  * The code contained herein is licensed under the GNU General Public
@@ -14,16 +14,19 @@
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/irq.h>
+#include <linux/genalloc.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mfd/syscon/imx6q-iomuxc-gpr.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/of_platform.h>
 #include <linux/regmap.h>
 #include <linux/suspend.h>
 #include <asm/cacheflush.h>
+#include <asm/fncpy.h>
 #include <asm/proc-fns.h>
 #include <asm/suspend.h>
-#include <asm/hardware/cache-l2x0.h>
+#include <asm/tlb.h>
 
 #include "common.h"
 #include "hardware.h"
@@ -58,7 +61,85 @@
 #define CGPR                            0x64
 #define BM_CGPR_INT_MEM_CLK_LPM         (0x1 << 17)
 
+#define MX6Q_SUSPEND_OCRAM_SIZE         0x1000
+#define MX6_MAX_MMDC_IO_NUM             33
+
 static void __iomem *ccm_base;
+static void __iomem *suspend_ocram_base;
+static void (*imx6_suspend_in_ocram_fn)(void __iomem *ocram_vbase);
+
+/*
+ * suspend ocram space layout:
+ * ======================== high address ======================
+ *                              .
+ *                              .
+ *                              .
+ *                              ^
+ *                              ^
+ *                              ^
+ *                      imx6_suspend code
+ *              PM_INFO structure(imx6_cpu_pm_info)
+ * ======================== low address =======================
+ */
+
+struct imx6_pm_base {
+        phys_addr_t pbase;
+        void __iomem *vbase;
+};
+
+struct imx6_pm_socdata {
+        u32 cpu_type;
+        const char *mmdc_compat;
+        const char *src_compat;
+        const char *iomuxc_compat;
+        const char *gpc_compat;
+        const u32 mmdc_io_num;
+        const u32 *mmdc_io_offset;
+};
+
+static const u32 imx6q_mmdc_io_offset[] __initconst = {
+        0x5ac, 0x5b4, 0x528, 0x520, /* DQM0 ~ DQM3 */
+        0x514, 0x510, 0x5bc, 0x5c4, /* DQM4 ~ DQM7 */
+        0x56c, 0x578, 0x588, 0x594, /* CAS, RAS, SDCLK_0, SDCLK_1 */
+        0x5a8, 0x5b0, 0x524, 0x51c, /* SDQS0 ~ SDQS3 */
+        0x518, 0x50c, 0x5b8, 0x5c0, /* SDQS4 ~ SDQS7 */
+        0x784, 0x788, 0x794, 0x79c, /* GPR_B0DS ~ GPR_B3DS */
+        0x7a0, 0x7a4, 0x7a8, 0x748, /* GPR_B4DS ~ GPR_B7DS */
+        0x59c, 0x5a0, 0x750, 0x774, /* SODT0, SODT1, MODE_CTL, MODE */
+        0x74c,                      /* GPR_ADDS */
+};
+
+static const struct imx6_pm_socdata imx6q_pm_data __initconst = {
+        .cpu_type = MXC_CPU_IMX6Q,
+        .mmdc_compat = "fsl,imx6q-mmdc",
+        .src_compat = "fsl,imx6q-src",
+        .iomuxc_compat = "fsl,imx6q-iomuxc",
+        .gpc_compat = "fsl,imx6q-gpc",
+        .mmdc_io_num = ARRAY_SIZE(imx6q_mmdc_io_offset),
+        .mmdc_io_offset = imx6q_mmdc_io_offset,
+};
+
+/*
+ * This structure is for passing necessary data for low level ocram
+ * suspend code(arch/arm/mach-imx/suspend-imx6.S), if this struct
+ * definition is changed, the offset definition in
+ * arch/arm/mach-imx/suspend-imx6.S must be also changed accordingly,
+ * otherwise, the suspend to ocram function will be broken!
+ */
+struct imx6_cpu_pm_info {
+        phys_addr_t pbase; /* The physical address of pm_info. */
+        phys_addr_t resume_addr; /* The physical resume address for asm code */
+        u32 cpu_type;
+        u32 pm_info_size; /* Size of pm_info. */
+        struct imx6_pm_base mmdc_base;
+        struct imx6_pm_base src_base;
+        struct imx6_pm_base iomuxc_base;
+        struct imx6_pm_base ccm_base;
+        struct imx6_pm_base gpc_base;
+        struct imx6_pm_base l2_base;
+        u32 mmdc_io_num; /* Number of MMDC IOs which need saved/restored. */
+        u32 mmdc_io_val[MX6_MAX_MMDC_IO_NUM][2]; /* To save offset and value */
+} __aligned(8);
 
 void imx6q_set_int_mem_clk_lpm(void)
 {
@@ -177,7 +258,17 @@ int imx6q_set_lpm(enum mxc_cpu_pwr_mode mode)
 
 static int imx6q_suspend_finish(unsigned long val)
 {
-        cpu_do_idle();
+        if (!imx6_suspend_in_ocram_fn) {
+                cpu_do_idle();
+        } else {
+                /*
+                 * call low level suspend function in ocram,
+                 * as we need to float DDR IO.
+                 */
+                local_flush_tlb_all();
+                imx6_suspend_in_ocram_fn(suspend_ocram_base);
+        }
+
         return 0;
 }
 
@@ -187,7 +278,12 @@ static int imx6q_pm_enter(suspend_state_t state)
         case PM_SUSPEND_MEM:
                 imx6q_set_lpm(STOP_POWER_OFF);
                 imx6q_enable_wb(true);
-                imx6q_enable_rbc(true);
+                /*
+                 * For suspend into ocram, asm code already take care of
+                 * RBC setting, so we do NOT need to do that here.
+                 */
+                if (!imx6_suspend_in_ocram_fn)
+                        imx6q_enable_rbc(true);
                 imx_gpc_pre_suspend();
                 imx_anatop_pre_suspend();
                 imx_set_cpu_jump(0, v7_cpu_resume);
@@ -218,12 +314,172 @@ void __init imx6q_pm_set_ccm_base(void __iomem *base)
         ccm_base = base;
 }
 
-void __init imx6q_pm_init(void)
+static int __init imx6_pm_get_base(struct imx6_pm_base *base,
+                                const char *compat)
+{
+        struct device_node *node;
+        struct resource res;
+        int ret = 0;
+
+        node = of_find_compatible_node(NULL, NULL, compat);
+        if (!node) {
+                ret = -ENODEV;
+                goto out;
+        }
+
+        ret = of_address_to_resource(node, 0, &res);
+        if (ret)
+                goto put_node;
+
+        base->pbase = res.start;
+        base->vbase = ioremap(res.start, resource_size(&res));
+        if (!base->vbase)
+                ret = -ENOMEM;
+
+put_node:
+        of_node_put(node);
+out:
+        return ret;
+}
+
+static int __init imx6q_ocram_suspend_init(const struct imx6_pm_socdata
+                                        *socdata)
+{
+        phys_addr_t ocram_pbase;
+        struct device_node *node;
+        struct platform_device *pdev;
+        struct imx6_cpu_pm_info *pm_info;
+        struct gen_pool *ocram_pool;
+        unsigned long ocram_base;
+        int i, ret = 0;
+        const u32 *mmdc_offset_array;
+
+        if (!socdata) {
+                pr_warn("%s: invalid argument!\n", __func__);
+                return -EINVAL;
+        }
+
+        node = of_find_compatible_node(NULL, NULL, "mmio-sram");
+        if (!node) {
+                pr_warn("%s: failed to find ocram node!\n", __func__);
+                return -ENODEV;
+        }
+
+        pdev = of_find_device_by_node(node);
+        if (!pdev) {
+                pr_warn("%s: failed to find ocram device!\n", __func__);
+                ret = -ENODEV;
+                goto put_node;
+        }
+
+        ocram_pool = dev_get_gen_pool(&pdev->dev);
+        if (!ocram_pool) {
+                pr_warn("%s: ocram pool unavailable!\n", __func__);
+                ret = -ENODEV;
+                goto put_node;
+        }
+
+        ocram_base = gen_pool_alloc(ocram_pool, MX6Q_SUSPEND_OCRAM_SIZE);
+        if (!ocram_base) {
+                pr_warn("%s: unable to alloc ocram!\n", __func__);
+                ret = -ENOMEM;
+                goto put_node;
+        }
+
+        ocram_pbase = gen_pool_virt_to_phys(ocram_pool, ocram_base);
+
+        suspend_ocram_base = __arm_ioremap_exec(ocram_pbase,
+                MX6Q_SUSPEND_OCRAM_SIZE, false);
+
+        pm_info = suspend_ocram_base;
+        pm_info->pbase = ocram_pbase;
+        pm_info->resume_addr = virt_to_phys(v7_cpu_resume);
+        pm_info->pm_info_size = sizeof(*pm_info);
+
+        /*
+         * ccm physical address is not used by asm code currently,
+         * so get ccm virtual address directly, as we already have
+         * it from ccm driver.
+         */
+        pm_info->ccm_base.vbase = ccm_base;
+
+        ret = imx6_pm_get_base(&pm_info->mmdc_base, socdata->mmdc_compat);
+        if (ret) {
+                pr_warn("%s: failed to get mmdc base %d!\n", __func__, ret);
+                goto put_node;
+        }
+
+        ret = imx6_pm_get_base(&pm_info->src_base, socdata->src_compat);
+        if (ret) {
+                pr_warn("%s: failed to get src base %d!\n", __func__, ret);
+                goto src_map_failed;
+        }
+
+        ret = imx6_pm_get_base(&pm_info->iomuxc_base, socdata->iomuxc_compat);
+        if (ret) {
+                pr_warn("%s: failed to get iomuxc base %d!\n", __func__, ret);
+                goto iomuxc_map_failed;
+        }
+
+        ret = imx6_pm_get_base(&pm_info->gpc_base, socdata->gpc_compat);
+        if (ret) {
+                pr_warn("%s: failed to get gpc base %d!\n", __func__, ret);
+                goto gpc_map_failed;
+        }
+
+        ret = imx6_pm_get_base(&pm_info->l2_base, "arm,pl310-cache");
+        if (ret) {
+                pr_warn("%s: failed to get pl310-cache base %d!\n",
+                        __func__, ret);
+                goto pl310_cache_map_failed;
+        }
+
+        pm_info->cpu_type = socdata->cpu_type;
+        pm_info->mmdc_io_num = socdata->mmdc_io_num;
+        mmdc_offset_array = socdata->mmdc_io_offset;
+
+        for (i = 0; i < pm_info->mmdc_io_num; i++) {
+                pm_info->mmdc_io_val[i][0] =
+                        mmdc_offset_array[i];
+                pm_info->mmdc_io_val[i][1] =
+                        readl_relaxed(pm_info->iomuxc_base.vbase +
+                        mmdc_offset_array[i]);
+        }
+
+        imx6_suspend_in_ocram_fn = fncpy(
+                suspend_ocram_base + sizeof(*pm_info),
+                &imx6_suspend,
+                MX6Q_SUSPEND_OCRAM_SIZE - sizeof(*pm_info));
+
+        goto put_node;
+
+pl310_cache_map_failed:
+        iounmap(&pm_info->gpc_base.vbase);
+gpc_map_failed:
+        iounmap(&pm_info->iomuxc_base.vbase);
+iomuxc_map_failed:
+        iounmap(&pm_info->src_base.vbase);
+src_map_failed:
+        iounmap(&pm_info->mmdc_base.vbase);
+put_node:
+        of_node_put(node);
+
+        return ret;
+}
+
+static void __init imx6_pm_common_init(const struct imx6_pm_socdata
+                                        *socdata)
 {
         struct regmap *gpr;
+        int ret;
 
         WARN_ON(!ccm_base);
 
+        ret = imx6q_ocram_suspend_init(socdata);
+        if (ret)
+                pr_warn("%s: failed to initialize ocram suspend %d!\n",
+                        __func__, ret);
+
         /*
          * This is for SW workaround step #1 of ERR007265, see comments
          * in imx6q_set_lpm for details of this errata.
@@ -239,3 +495,18 @@ void __init imx6q_pm_init(void)
 
         suspend_set_ops(&imx6q_pm_ops);
 }
+
+void __init imx6q_pm_init(void)
+{
+        imx6_pm_common_init(&imx6q_pm_data);
+}
+
+void __init imx6dl_pm_init(void)
+{
+        imx6_pm_common_init(NULL);
+}
+
+void __init imx6sl_pm_init(void)
+{
+        imx6_pm_common_init(NULL);
+}
diff --git a/arch/arm/mach-imx/suspend-imx6.S b/arch/arm/mach-imx/suspend-imx6.S
new file mode 100644
index 000000000000..d273ee7ecc36
--- /dev/null
+++ b/arch/arm/mach-imx/suspend-imx6.S
@@ -0,0 +1,289 @@
+/*
+ * Copyright 2014 Freescale Semiconductor, Inc.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/linkage.h>
+#include <asm/hardware/cache-l2x0.h>
+#include "hardware.h"
+
+/*
+ * ==================== low level suspend ====================
+ *
+ * Better to follow below rules to use ARM registers:
+ * r0: pm_info structure address;
+ * r1 ~ r4: for saving pm_info members;
+ * r5 ~ r10: free registers;
+ * r11: io base address.
+ *
+ * suspend ocram space layout:
+ * ======================== high address ======================
+ *                              .
+ *                              .
+ *                              .
+ *                              ^
+ *                              ^
+ *                              ^
+ *                      imx6_suspend code
+ *              PM_INFO structure(imx6_cpu_pm_info)
+ * ======================== low address =======================
+ */
+
+/*
+ * Below offsets are based on struct imx6_cpu_pm_info
+ * which defined in arch/arm/mach-imx/pm-imx6q.c, this
+ * structure contains necessary pm info for low level
+ * suspend related code.
+ */
+#define PM_INFO_PBASE_OFFSET                    0x0
+#define PM_INFO_RESUME_ADDR_OFFSET              0x4
+#define PM_INFO_CPU_TYPE_OFFSET                 0x8
+#define PM_INFO_PM_INFO_SIZE_OFFSET             0xC
+#define PM_INFO_MX6Q_MMDC_P_OFFSET              0x10
+#define PM_INFO_MX6Q_MMDC_V_OFFSET              0x14
+#define PM_INFO_MX6Q_SRC_P_OFFSET               0x18
+#define PM_INFO_MX6Q_SRC_V_OFFSET               0x1C
+#define PM_INFO_MX6Q_IOMUXC_P_OFFSET            0x20
+#define PM_INFO_MX6Q_IOMUXC_V_OFFSET            0x24
+#define PM_INFO_MX6Q_CCM_P_OFFSET               0x28
+#define PM_INFO_MX6Q_CCM_V_OFFSET               0x2C
+#define PM_INFO_MX6Q_GPC_P_OFFSET               0x30
+#define PM_INFO_MX6Q_GPC_V_OFFSET               0x34
+#define PM_INFO_MX6Q_L2_P_OFFSET                0x38
+#define PM_INFO_MX6Q_L2_V_OFFSET                0x3C
+#define PM_INFO_MMDC_IO_NUM_OFFSET              0x40
+#define PM_INFO_MMDC_IO_VAL_OFFSET              0x44
+
+#define MX6Q_SRC_GPR1   0x20
+#define MX6Q_SRC_GPR2   0x24
+#define MX6Q_MMDC_MAPSR 0x404
+#define MX6Q_GPC_IMR1   0x08
+#define MX6Q_GPC_IMR2   0x0c
+#define MX6Q_GPC_IMR3   0x10
+#define MX6Q_GPC_IMR4   0x14
+#define MX6Q_CCM_CCR    0x0
+
+        .align 3
+
+        .macro  sync_l2_cache
+
+        /* sync L2 cache to drain L2's buffers to DRAM. */
+#ifdef CONFIG_CACHE_L2X0
+        ldr     r11, [r0, #PM_INFO_MX6Q_L2_V_OFFSET]
+        mov     r6, #0x0
+        str     r6, [r11, #L2X0_CACHE_SYNC]
+1:
+        ldr     r6, [r11, #L2X0_CACHE_SYNC]
+        ands    r6, r6, #0x1
+        bne     1b
+#endif
+
+        .endm
+
+        .macro  resume_mmdc
+
+        /* restore MMDC IO */
+        cmp     r5, #0x0
+        ldreq   r11, [r0, #PM_INFO_MX6Q_IOMUXC_V_OFFSET]
+        ldrne   r11, [r0, #PM_INFO_MX6Q_IOMUXC_P_OFFSET]
+
+        ldr     r6, [r0, #PM_INFO_MMDC_IO_NUM_OFFSET]
+        ldr     r7, =PM_INFO_MMDC_IO_VAL_OFFSET
+        add     r7, r7, r0
+1:
+        ldr     r8, [r7], #0x4
+        ldr     r9, [r7], #0x4
+        str     r9, [r11, r8]
+        subs    r6, r6, #0x1
+        bne     1b
+
+        cmp     r5, #0x0
+        ldreq   r11, [r0, #PM_INFO_MX6Q_MMDC_V_OFFSET]
+        ldrne   r11, [r0, #PM_INFO_MX6Q_MMDC_P_OFFSET]
+
+        /* let DDR out of self-refresh */
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        bic     r7, r7, #(1 << 21)
+        str     r7, [r11, #MX6Q_MMDC_MAPSR]
+2:
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        ands    r7, r7, #(1 << 25)
+        bne     2b
+
+        /* enable DDR auto power saving */
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        bic     r7, r7, #0x1
+        str     r7, [r11, #MX6Q_MMDC_MAPSR]
+
+        .endm
+
+ENTRY(imx6_suspend)
+        ldr     r1, [r0, #PM_INFO_PBASE_OFFSET]
+        ldr     r2, [r0, #PM_INFO_RESUME_ADDR_OFFSET]
+        ldr     r3, [r0, #PM_INFO_CPU_TYPE_OFFSET]
+        ldr     r4, [r0, #PM_INFO_PM_INFO_SIZE_OFFSET]
+
+        /*
+         * counting the resume address in iram
+         * to set it in SRC register.
+         */
+        ldr     r6, =imx6_suspend
+        ldr     r7, =resume
+        sub     r7, r7, r6
+        add     r8, r1, r4
+        add     r9, r8, r7
+
+        /*
+         * make sure TLB contain the addr we want,
+         * as we will access them after MMDC IO floated.
+         */
+
+        ldr     r11, [r0, #PM_INFO_MX6Q_CCM_V_OFFSET]
+        ldr     r6, [r11, #0x0]
+        ldr     r11, [r0, #PM_INFO_MX6Q_GPC_V_OFFSET]
+        ldr     r6, [r11, #0x0]
+
+        /* use r11 to store the IO address */
+        ldr     r11, [r0, #PM_INFO_MX6Q_SRC_V_OFFSET]
+        /* store physical resume addr and pm_info address. */
+        str     r9, [r11, #MX6Q_SRC_GPR1]
+        str     r1, [r11, #MX6Q_SRC_GPR2]
+
+        /* need to sync L2 cache before DSM. */
+        sync_l2_cache
+
+        ldr     r11, [r0, #PM_INFO_MX6Q_MMDC_V_OFFSET]
+        /*
+         * put DDR explicitly into self-refresh and
+         * disable automatic power savings.
+         */
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        orr     r7, r7, #0x1
+        str     r7, [r11, #MX6Q_MMDC_MAPSR]
+
+        /* make the DDR explicitly enter self-refresh. */
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        orr     r7, r7, #(1 << 21)
+        str     r7, [r11, #MX6Q_MMDC_MAPSR]
+
+poll_dvfs_set:
+        ldr     r7, [r11, #MX6Q_MMDC_MAPSR]
+        ands    r7, r7, #(1 << 25)
+        beq     poll_dvfs_set
+
+        ldr     r11, [r0, #PM_INFO_MX6Q_IOMUXC_V_OFFSET]
+        ldr     r6, =0x0
+        ldr     r7, [r0, #PM_INFO_MMDC_IO_NUM_OFFSET]
+        ldr     r8, =PM_INFO_MMDC_IO_VAL_OFFSET
+        add     r8, r8, r0
+set_mmdc_io_lpm:
+        ldr     r9, [r8], #0x8
+        str     r6, [r11, r9]
+        subs    r7, r7, #0x1
+        bne     set_mmdc_io_lpm
+
+        /*
+         * mask all GPC interrupts before
+         * enabling the RBC counters to
+         * avoid the counter starting too
+         * early if an interupt is already
+         * pending.
+         */
+        ldr     r11, [r0, #PM_INFO_MX6Q_GPC_V_OFFSET]
+        ldr     r6, [r11, #MX6Q_GPC_IMR1]
+        ldr     r7, [r11, #MX6Q_GPC_IMR2]
+        ldr     r8, [r11, #MX6Q_GPC_IMR3]
+        ldr     r9, [r11, #MX6Q_GPC_IMR4]
+
+        ldr     r10, =0xffffffff
+        str     r10, [r11, #MX6Q_GPC_IMR1]
+        str     r10, [r11, #MX6Q_GPC_IMR2]
+        str     r10, [r11, #MX6Q_GPC_IMR3]
+        str     r10, [r11, #MX6Q_GPC_IMR4]
+
+        /*
+         * enable the RBC bypass counter here
+         * to hold off the interrupts. RBC counter
+         * = 32 (1ms), Minimum RBC delay should be
+         * 400us for the analog LDOs to power down.
+         */
+        ldr     r11, [r0, #PM_INFO_MX6Q_CCM_V_OFFSET]
+        ldr     r10, [r11, #MX6Q_CCM_CCR]
+        bic     r10, r10, #(0x3f << 21)
+        orr     r10, r10, #(0x20 << 21)
+        str     r10, [r11, #MX6Q_CCM_CCR]
+
+        /* enable the counter. */
+        ldr     r10, [r11, #MX6Q_CCM_CCR]
+        orr     r10, r10, #(0x1 << 27)
+        str     r10, [r11, #MX6Q_CCM_CCR]
+
+        /* unmask all the GPC interrupts. */
+        ldr     r11, [r0, #PM_INFO_MX6Q_GPC_V_OFFSET]
+        str     r6, [r11, #MX6Q_GPC_IMR1]
+        str     r7, [r11, #MX6Q_GPC_IMR2]
+        str     r8, [r11, #MX6Q_GPC_IMR3]
+        str     r9, [r11, #MX6Q_GPC_IMR4]
+
+        /*
+         * now delay for a short while (3usec)
+         * ARM is at 1GHz at this point
+         * so a short loop should be enough.
+         * this delay is required to ensure that
+         * the RBC counter can start counting in
+         * case an interrupt is already pending
+         * or in case an interrupt arrives just
+         * as ARM is about to assert DSM_request.
+         */
+        ldr     r6, =2000
+rbc_loop:
+        subs    r6, r6, #0x1
+        bne     rbc_loop
+
+        /* Zzz, enter stop mode */
+        wfi
+        nop
+        nop
+        nop
+        nop
+
+        /*
+         * run to here means there is pending
+         * wakeup source, system should auto
+         * resume, we need to restore MMDC IO first
+         */
+        mov     r5, #0x0
+        resume_mmdc
+
+        /* return to suspend finish */
+        mov     pc, lr
+
+resume:
+        /* invalidate L1 I-cache first */
+        mov     r6, #0x0
+        mcr     p15, 0, r6, c7, c5, 0
+        mcr     p15, 0, r6, c7, c5, 6
+        /* enable the Icache and branch prediction */
+        mov     r6, #0x1800
+        mcr     p15, 0, r6, c1, c0, 0
+        isb
+
+        /* get physical resume address from pm_info. */
+        ldr     lr, [r0, #PM_INFO_RESUME_ADDR_OFFSET]
+        /* clear core0's entry and parameter */
+        ldr     r11, [r0, #PM_INFO_MX6Q_SRC_P_OFFSET]
+        mov     r7, #0x0
+        str     r7, [r11, #MX6Q_SRC_GPR1]
+        str     r7, [r11, #MX6Q_SRC_GPR2]
+
+        mov     r5, #0x1
+        resume_mmdc
+
+        mov     pc, lr
+ENDPROC(imx6_suspend)