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>

1 files changed, 245 insertions, 0 deletions

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);