avr32: Power Management support ("standby" and "mem" modes)

Implement Standby support. In this mode, we'll suspend all drivers,
put the SDRAM in self-refresh mode and switch off the HSB bus
("frozen" mode.)

Implement Suspend-to-mem support. In this mode, we suspend all
drivers, put the SDRAM into self-refresh mode and switch off all
internal clocks except the 32 kHz oscillator ("stop" mode.)

The lowest-level suspend code runs from a small portion of SRAM
allocated at startup time. This gets rid of a small potential race
with the SDRAM where we might try to enter self-refresh mode in the
middle of an icache burst. We also relocate all interrupt and
exception handlers to SRAM during the small window when we enter and
exit the low-power modes.

We don't need to do any special tricks to start and stop the PLL. The
main clock is automatically gated by hardware until the PLL is stable.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

5 files changed, 487 insertions, 1 deletions

diff --git a/arch/avr32/mach-at32ap/Makefile b/arch/avr32/mach-at32ap/Makefile
index cb44182d386..d5018e2eed2 100644
--- a/arch/avr32/mach-at32ap/Makefile
+++ b/arch/avr32/mach-at32ap/Makefile
@@ -1,3 +1,8 @@
 obj-y                           += pdc.o clock.o intc.o extint.o pio.o hsmc.o
 obj-$(CONFIG_CPU_AT32AP700X)    += at32ap700x.o pm-at32ap700x.o
 obj-$(CONFIG_CPU_FREQ_AT32AP)   += cpufreq.o
+obj-$(CONFIG_PM)                += pm.o
+
+ifeq ($(CONFIG_PM_DEBUG),y)
+CFLAGS_pm.o     += -DDEBUG
+endif
diff --git a/arch/avr32/mach-at32ap/intc.c b/arch/avr32/mach-at32ap/intc.c
index 644a3fb8c16..994c4545e2b 100644
--- a/arch/avr32/mach-at32ap/intc.c
+++ b/arch/avr32/mach-at32ap/intc.c
@@ -22,6 +22,10 @@ struct intc {
         void __iomem            *regs;
         struct irq_chip         chip;
         struct sys_device       sysdev;
+#ifdef CONFIG_PM
+        unsigned long           suspend_ipr;
+        unsigned long           saved_ipr[64];
+#endif
 };
 
 extern struct platform_device at32_intc0_device;
@@ -138,8 +142,56 @@ fail:
         panic("Interrupt controller initialization failed!\n");
 }
 
+#ifdef CONFIG_PM
+void intc_set_suspend_handler(unsigned long offset)
+{
+        intc0.suspend_ipr = offset;
+}
+
+static int intc_suspend(struct sys_device *sdev, pm_message_t state)
+{
+        struct intc *intc = container_of(sdev, struct intc, sysdev);
+        int i;
+
+        if (unlikely(!irqs_disabled())) {
+                pr_err("intc_suspend: called with interrupts enabled\n");
+                return -EINVAL;
+        }
+
+        if (unlikely(!intc->suspend_ipr)) {
+                pr_err("intc_suspend: suspend_ipr not initialized\n");
+                return -EINVAL;
+        }
+
+        for (i = 0; i < 64; i++) {
+                intc->saved_ipr[i] = intc_readl(intc, INTPR0 + 4 * i);
+                intc_writel(intc, INTPR0 + 4 * i, intc->suspend_ipr);
+        }
+
+        return 0;
+}
+
+static int intc_resume(struct sys_device *sdev)
+{
+        struct intc *intc = container_of(sdev, struct intc, sysdev);
+        int i;
+
+        WARN_ON(!irqs_disabled());
+
+        for (i = 0; i < 64; i++)
+                intc_writel(intc, INTPR0 + 4 * i, intc->saved_ipr[i]);
+
+        return 0;
+}
+#else
+#define intc_suspend    NULL
+#define intc_resume     NULL
+#endif
+
 static struct sysdev_class intc_class = {
-        .name   = "intc",
+        .name           = "intc",
+        .suspend        = intc_suspend,
+        .resume         = intc_resume,
 };
 
 static int __init intc_init_sysdev(void)
diff --git a/arch/avr32/mach-at32ap/pm-at32ap700x.S b/arch/avr32/mach-at32ap/pm-at32ap700x.S
index 949e2485e27..0a53ad314ff 100644
--- a/arch/avr32/mach-at32ap/pm-at32ap700x.S
+++ b/arch/avr32/mach-at32ap/pm-at32ap700x.S
@@ -12,6 +12,12 @@
 #include <asm/thread_info.h>
 #include <asm/arch/pm.h>
 
+#include "pm.h"
+#include "sdramc.h"
+
+/* Same as 0xfff00000 but fits in a 21 bit signed immediate */
+#define PM_BASE -0x100000
+
         .section .bss, "wa", @nobits
         .global disable_idle_sleep
         .type   disable_idle_sleep, @object
@@ -64,3 +70,105 @@ cpu_idle_skip_sleep:
         unmask_interrupts
         retal   r12
         .size   cpu_idle_skip_sleep, . - cpu_idle_skip_sleep
+
+#ifdef CONFIG_PM
+        .section .init.text, "ax", @progbits
+
+        .global pm_exception
+        .type   pm_exception, @function
+pm_exception:
+        /*
+         * Exceptions are masked when we switch to this handler, so
+         * we'll only get "unrecoverable" exceptions (offset 0.)
+         */
+        sub     r12, pc, . - .Lpanic_msg
+        lddpc   pc, .Lpanic_addr
+
+        .align  2
+.Lpanic_addr:
+        .long   panic
+.Lpanic_msg:
+        .asciz  "Unrecoverable exception during suspend\n"
+        .size   pm_exception, . - pm_exception
+
+        .global pm_irq0
+        .type   pm_irq0, @function
+pm_irq0:
+        /* Disable interrupts and return after the sleep instruction */
+        mfsr    r9, SYSREG_RSR_INT0
+        mtsr    SYSREG_RAR_INT0, r8
+        sbr     r9, SYSREG_GM_OFFSET
+        mtsr    SYSREG_RSR_INT0, r9
+        rete
+
+        /*
+         * void cpu_enter_standby(unsigned long sdramc_base)
+         *
+         * Enter PM_SUSPEND_STANDBY mode. At this point, all drivers
+         * are suspended and interrupts are disabled. Interrupts
+         * marked as 'wakeup' event sources may still come along and
+         * get us out of here.
+         *
+         * The SDRAM will be put into self-refresh mode (which does
+         * not require a clock from the CPU), and the CPU will be put
+         * into "frozen" mode (HSB bus stopped). The SDRAM controller
+         * will automatically bring the SDRAM into normal mode on the
+         * first access, and the power manager will automatically
+         * start the HSB and CPU clocks upon a wakeup event.
+         *
+         * This code uses the same "skip sleep" technique as above.
+         * It is very important that we jump directly to
+         * cpu_after_sleep after the sleep instruction since that's
+         * where we'll end up if the interrupt handler decides that we
+         * need to skip the sleep instruction.
+         */
+        .global pm_standby
+        .type   pm_standby, @function
+pm_standby:
+        /*
+         * interrupts are already masked at this point, and EVBA
+         * points to pm_exception above.
+         */
+        ld.w    r10, r12[SDRAMC_LPR]
+        sub     r8, pc, . - 1f          /* return address for irq handler */
+        mov     r11, SDRAMC_LPR_LPCB_SELF_RFR
+        bfins   r10, r11, 0, 2          /* LPCB <- self Refresh */
+        sync    0                       /* flush write buffer */
+        st.w    r12[SDRAMC_LPR], r11    /* put SDRAM in self-refresh mode */
+        ld.w    r11, r12[SDRAMC_LPR]
+        unmask_interrupts
+        sleep   CPU_SLEEP_FROZEN
+1:      mask_interrupts
+        retal   r12
+        .size   pm_standby, . - pm_standby
+
+        .global pm_suspend_to_ram
+        .type   pm_suspend_to_ram, @function
+pm_suspend_to_ram:
+        /*
+         * interrupts are already masked at this point, and EVBA
+         * points to pm_exception above.
+         */
+        mov     r11, 0
+        cache   r11[2], 8               /* clean all dcache lines */
+        sync    0                       /* flush write buffer */
+        ld.w    r10, r12[SDRAMC_LPR]
+        sub     r8, pc, . - 1f          /* return address for irq handler */
+        mov     r11, SDRAMC_LPR_LPCB_SELF_RFR
+        bfins   r10, r11, 0, 2          /* LPCB <- self refresh */
+        st.w    r12[SDRAMC_LPR], r10    /* put SDRAM in self-refresh mode */
+        ld.w    r11, r12[SDRAMC_LPR]
+
+        unmask_interrupts
+        sleep   CPU_SLEEP_STOP
+1:      mask_interrupts
+
+        retal   r12
+        .size   pm_suspend_to_ram, . - pm_suspend_to_ram
+
+        .global pm_sram_end
+        .type   pm_sram_end, @function
+pm_sram_end:
+        .size   pm_sram_end, 0
+
+#endif /* CONFIG_PM */
diff --git a/arch/avr32/mach-at32ap/pm.c b/arch/avr32/mach-at32ap/pm.c
new file mode 100644
index 00000000000..0b764320135
--- /dev/null
+++ b/arch/avr32/mach-at32ap/pm.c
@@ -0,0 +1,245 @@
+/*
+ * AVR32 AP Power Management
+ *
+ * Copyright (C) 2008 Atmel Corporation
+ *
+ * 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/io.h>
+#include <linux/suspend.h>
+#include <linux/vmalloc.h>
+
+#include <asm/cacheflush.h>
+#include <asm/sysreg.h>
+
+#include <asm/arch/pm.h>
+#include <asm/arch/sram.h>
+
+/* FIXME: This is only valid for AP7000 */
+#define SDRAMC_BASE     0xfff03800
+
+#include "sdramc.h"
+
+#define SRAM_PAGE_FLAGS (SYSREG_BIT(TLBELO_D) | SYSREG_BF(SZ, 1)        \
+                                | SYSREG_BF(AP, 3) | SYSREG_BIT(G))
+
+
+static unsigned long    pm_sram_start;
+static size_t           pm_sram_size;
+static struct vm_struct *pm_sram_area;
+
+static void (*avr32_pm_enter_standby)(unsigned long sdramc_base);
+static void (*avr32_pm_enter_str)(unsigned long sdramc_base);
+
+/*
+ * Must be called with interrupts disabled. Exceptions will be masked
+ * on return (i.e. all exceptions will be "unrecoverable".)
+ */
+static void *avr32_pm_map_sram(void)
+{
+        unsigned long   vaddr;
+        unsigned long   page_addr;
+        u32             tlbehi;
+        u32             mmucr;
+
+        vaddr = (unsigned long)pm_sram_area->addr;
+        page_addr = pm_sram_start & PAGE_MASK;
+
+        /*
+         * Mask exceptions and grab the first TLB entry. We won't be
+         * needing it while sleeping.
+         */
+        asm volatile("ssrf      %0" : : "i"(SYSREG_EM_OFFSET) : "memory");
+
+        mmucr = sysreg_read(MMUCR);
+        tlbehi = sysreg_read(TLBEHI);
+        sysreg_write(MMUCR, SYSREG_BFINS(DRP, 0, mmucr));
+
+        tlbehi = SYSREG_BF(ASID, SYSREG_BFEXT(ASID, tlbehi));
+        tlbehi |= vaddr & PAGE_MASK;
+        tlbehi |= SYSREG_BIT(TLBEHI_V);
+
+        sysreg_write(TLBELO, page_addr | SRAM_PAGE_FLAGS);
+        sysreg_write(TLBEHI, tlbehi);
+        __builtin_tlbw();
+
+        return (void *)(vaddr + pm_sram_start - page_addr);
+}
+
+/*
+ * Must be called with interrupts disabled. Exceptions will be
+ * unmasked on return.
+ */
+static void avr32_pm_unmap_sram(void)
+{
+        u32     mmucr;
+        u32     tlbehi;
+        u32     tlbarlo;
+
+        /* Going to update TLB entry at index 0 */
+        mmucr = sysreg_read(MMUCR);
+        tlbehi = sysreg_read(TLBEHI);
+        sysreg_write(MMUCR, SYSREG_BFINS(DRP, 0, mmucr));
+
+        /* Clear the "valid" bit */
+        tlbehi = SYSREG_BF(ASID, SYSREG_BFEXT(ASID, tlbehi));
+        sysreg_write(TLBEHI, tlbehi);
+
+        /* Mark it as "not accessed" */
+        tlbarlo = sysreg_read(TLBARLO);
+        sysreg_write(TLBARLO, tlbarlo | 0x80000000U);
+
+        /* Update the TLB */
+        __builtin_tlbw();
+
+        /* Unmask exceptions */
+        asm volatile("csrf      %0" : : "i"(SYSREG_EM_OFFSET) : "memory");
+}
+
+static int avr32_pm_valid_state(suspend_state_t state)
+{
+        switch (state) {
+        case PM_SUSPEND_ON:
+        case PM_SUSPEND_STANDBY:
+        case PM_SUSPEND_MEM:
+                return 1;
+
+        default:
+                return 0;
+        }
+}
+
+static int avr32_pm_enter(suspend_state_t state)
+{
+        u32             lpr_saved;
+        u32             evba_saved;
+        void            *sram;
+
+        switch (state) {
+        case PM_SUSPEND_STANDBY:
+                sram = avr32_pm_map_sram();
+
+                /* Switch to in-sram exception handlers */
+                evba_saved = sysreg_read(EVBA);
+                sysreg_write(EVBA, (unsigned long)sram);
+
+                /*
+                 * Save the LPR register so that we can re-enable
+                 * SDRAM Low Power mode on resume.
+                 */
+                lpr_saved = sdramc_readl(LPR);
+                pr_debug("%s: Entering standby...\n", __func__);
+                avr32_pm_enter_standby(SDRAMC_BASE);
+                sdramc_writel(LPR, lpr_saved);
+
+                /* Switch back to regular exception handlers */
+                sysreg_write(EVBA, evba_saved);
+
+                avr32_pm_unmap_sram();
+                break;
+
+        case PM_SUSPEND_MEM:
+                sram = avr32_pm_map_sram();
+
+                /* Switch to in-sram exception handlers */
+                evba_saved = sysreg_read(EVBA);
+                sysreg_write(EVBA, (unsigned long)sram);
+
+                /*
+                 * Save the LPR register so that we can re-enable
+                 * SDRAM Low Power mode on resume.
+                 */
+                lpr_saved = sdramc_readl(LPR);
+                pr_debug("%s: Entering suspend-to-ram...\n", __func__);
+                avr32_pm_enter_str(SDRAMC_BASE);
+                sdramc_writel(LPR, lpr_saved);
+
+                /* Switch back to regular exception handlers */
+                sysreg_write(EVBA, evba_saved);
+
+                avr32_pm_unmap_sram();
+                break;
+
+        case PM_SUSPEND_ON:
+                pr_debug("%s: Entering idle...\n", __func__);
+                cpu_enter_idle();
+                break;
+
+        default:
+                pr_debug("%s: Invalid suspend state %d\n", __func__, state);
+                goto out;
+        }
+
+        pr_debug("%s: wakeup\n", __func__);
+
+out:
+        return 0;
+}
+
+static struct platform_suspend_ops avr32_pm_ops = {
+        .valid  = avr32_pm_valid_state,
+        .enter  = avr32_pm_enter,
+};
+
+static unsigned long avr32_pm_offset(void *symbol)
+{
+        extern u8 pm_exception[];
+
+        return (unsigned long)symbol - (unsigned long)pm_exception;
+}
+
+static int __init avr32_pm_init(void)
+{
+        extern u8 pm_exception[];
+        extern u8 pm_irq0[];
+        extern u8 pm_standby[];
+        extern u8 pm_suspend_to_ram[];
+        extern u8 pm_sram_end[];
+        void *dst;
+
+        /*
+         * To keep things simple, we depend on not needing more than a
+         * single page.
+         */
+        pm_sram_size = avr32_pm_offset(pm_sram_end);
+        if (pm_sram_size > PAGE_SIZE)
+                goto err;
+
+        pm_sram_start = sram_alloc(pm_sram_size);
+        if (!pm_sram_start)
+                goto err_alloc_sram;
+
+        /* Grab a virtual area we can use later on. */
+        pm_sram_area = get_vm_area(pm_sram_size, VM_IOREMAP);
+        if (!pm_sram_area)
+                goto err_vm_area;
+        pm_sram_area->phys_addr = pm_sram_start;
+
+        local_irq_disable();
+        dst = avr32_pm_map_sram();
+        memcpy(dst, pm_exception, pm_sram_size);
+        flush_dcache_region(dst, pm_sram_size);
+        invalidate_icache_region(dst, pm_sram_size);
+        avr32_pm_unmap_sram();
+        local_irq_enable();
+
+        avr32_pm_enter_standby = dst + avr32_pm_offset(pm_standby);
+        avr32_pm_enter_str = dst + avr32_pm_offset(pm_suspend_to_ram);
+        intc_set_suspend_handler(avr32_pm_offset(pm_irq0));
+
+        suspend_set_ops(&avr32_pm_ops);
+
+        printk("AVR32 AP Power Management enabled\n");
+
+        return 0;
+
+err_vm_area:
+        sram_free(pm_sram_start, pm_sram_size);
+err_alloc_sram:
+err:
+        pr_err("AVR32 Power Management initialization failed\n");
+        return -ENOMEM;
+}
+arch_initcall(avr32_pm_init);
diff --git a/arch/avr32/mach-at32ap/sdramc.h b/arch/avr32/mach-at32ap/sdramc.h
new file mode 100644
index 00000000000..66eeaed4907
--- /dev/null
+++ b/arch/avr32/mach-at32ap/sdramc.h
@@ -0,0 +1,76 @@
+/*
+ * Register definitions for the AT32AP SDRAM Controller
+ *
+ * Copyright (C) 2008 Atmel Corporation
+ *
+ * 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.
+ */
+
+/* Register offsets */
+#define SDRAMC_MR                       0x0000
+#define SDRAMC_TR                       0x0004
+#define SDRAMC_CR                       0x0008
+#define SDRAMC_HSR                      0x000c
+#define SDRAMC_LPR                      0x0010
+#define SDRAMC_IER                      0x0014
+#define SDRAMC_IDR                      0x0018
+#define SDRAMC_IMR                      0x001c
+#define SDRAMC_ISR                      0x0020
+#define SDRAMC_MDR                      0x0024
+
+/* MR - Mode Register */
+#define SDRAMC_MR_MODE_NORMAL           (  0 <<  0)
+#define SDRAMC_MR_MODE_NOP              (  1 <<  0)
+#define SDRAMC_MR_MODE_BANKS_PRECHARGE  (  2 <<  0)
+#define SDRAMC_MR_MODE_LOAD_MODE        (  3 <<  0)
+#define SDRAMC_MR_MODE_AUTO_REFRESH     (  4 <<  0)
+#define SDRAMC_MR_MODE_EXT_LOAD_MODE    (  5 <<  0)
+#define SDRAMC_MR_MODE_POWER_DOWN       (  6 <<  0)
+
+/* CR - Configuration Register */
+#define SDRAMC_CR_NC_8_BITS             (  0 <<  0)
+#define SDRAMC_CR_NC_9_BITS             (  1 <<  0)
+#define SDRAMC_CR_NC_10_BITS            (  2 <<  0)
+#define SDRAMC_CR_NC_11_BITS            (  3 <<  0)
+#define SDRAMC_CR_NR_11_BITS            (  0 <<  2)
+#define SDRAMC_CR_NR_12_BITS            (  1 <<  2)
+#define SDRAMC_CR_NR_13_BITS            (  2 <<  2)
+#define SDRAMC_CR_NB_2_BANKS            (  0 <<  4)
+#define SDRAMC_CR_NB_4_BANKS            (  1 <<  4)
+#define SDRAMC_CR_CAS(x)                ((x) <<  5)
+#define SDRAMC_CR_DBW_32_BITS           (  0 <<  7)
+#define SDRAMC_CR_DBW_16_BITS           (  1 <<  7)
+#define SDRAMC_CR_TWR(x)                ((x) <<  8)
+#define SDRAMC_CR_TRC(x)                ((x) << 12)
+#define SDRAMC_CR_TRP(x)                ((x) << 16)
+#define SDRAMC_CR_TRCD(x)               ((x) << 20)
+#define SDRAMC_CR_TRAS(x)               ((x) << 24)
+#define SDRAMC_CR_TXSR(x)               ((x) << 28)
+
+/* HSR - High Speed Register */
+#define SDRAMC_HSR_DA                   (  1 <<  0)
+
+/* LPR - Low Power Register */
+#define SDRAMC_LPR_LPCB_INHIBIT         (  0 <<  0)
+#define SDRAMC_LPR_LPCB_SELF_RFR        (  1 <<  0)
+#define SDRAMC_LPR_LPCB_PDOWN           (  2 <<  0)
+#define SDRAMC_LPR_LPCB_DEEP_PDOWN      (  3 <<  0)
+#define SDRAMC_LPR_PASR(x)              ((x) <<  4)
+#define SDRAMC_LPR_TCSR(x)              ((x) <<  8)
+#define SDRAMC_LPR_DS(x)                ((x) << 10)
+#define SDRAMC_LPR_TIMEOUT(x)           ((x) << 12)
+
+/* IER/IDR/IMR/ISR - Interrupt Enable/Disable/Mask/Status Register */
+#define SDRAMC_ISR_RES                  (  1 <<  0)
+
+/* MDR - Memory Device Register */
+#define SDRAMC_MDR_MD_SDRAM             (  0 <<  0)
+#define SDRAMC_MDR_MD_LOW_PWR_SDRAM     (  1 <<  0)
+
+/* Register access macros */
+#define sdramc_readl(reg) \
+        __raw_readl((void __iomem __force *)SDRAMC_BASE + SDRAMC_##reg)
+#define sdramc_writel(reg, value) \
+        __raw_writel(value, (void __iomem __force *)SDRAMC_BASE + SDRAMC_##reg)