[ARM] 3605/1: AT91RM9200 Power Management

Patch from Andrew Victor

This patch adds the core Power Management support for the AT91RM9200
processor.  It will support suspend-to-RAM and standby modes.

The suspend-to-RAM functionality is not 100% complete.  The code that
needs to be execute from the internal SRAM to restore the system is
outstanding.  For now we just fall through to Standby mode.

The AT91-specific at91_suspend_entering_slow_clock() function will
eventually be replaced by clk_must_disable() once that functionality is
added to mainline clock API.

Patch from David Brownell.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 232 insertions, 0 deletions

diff --git a/arch/arm/mach-at91rm9200/generic.h b/arch/arm/mach-at91rm9200/generic.h
index 9bd541e..f0d969d 100644
--- a/arch/arm/mach-at91rm9200/generic.h
+++ b/arch/arm/mach-at91rm9200/generic.h
@@ -16,3 +16,10 @@ extern struct sys_timer at91rm9200_timer;
 extern void __init at91rm9200_map_io(void);
 
 extern int __init at91_clock_init(unsigned long main_clock);
+struct device;
+extern void __init at91_clock_associate(const char *id, struct device *dev, const char *func);
+
+ /* Power Management */
+extern void at91_irq_suspend(void);
+extern void at91_irq_resume(void);
+
diff --git a/arch/arm/mach-at91rm9200/pm.c b/arch/arm/mach-at91rm9200/pm.c
new file mode 100644
index 0000000..47e5480
--- /dev/null
+++ b/arch/arm/mach-at91rm9200/pm.c
@@ -0,0 +1,225 @@
+/*
+ * arch/arm/mach-at91rm9200/pm.c
+ * AT91 Power Management
+ *
+ * Copyright (C) 2005 David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/pm.h>
+#include <linux/sched.h>
+#include <linux/proc_fs.h>
+#include <linux/pm.h>
+#include <linux/interrupt.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/atomic.h>
+#include <asm/mach/time.h>
+#include <asm/mach/irq.h>
+#include <asm/mach-types.h>
+
+#include <asm/arch/gpio.h>
+
+#include "generic.h"
+
+
+static int at91_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 suspend_state_t target_state;
+
+/*
+ * Called after processes are frozen, but before we shutdown devices.
+ */
+static int at91_pm_prepare(suspend_state_t state)
+{
+	target_state = state;
+	return 0;
+}
+
+/*
+ * Verify that all the clocks are correct before entering
+ * slow-clock mode.
+ */
+static int at91_pm_verify_clocks(void)
+{
+	unsigned long scsr;
+	int i;
+
+	scsr = at91_sys_read(AT91_PMC_SCSR);
+
+	/* USB must not be using PLLB */
+	if ((scsr & (AT91_PMC_UHP | AT91_PMC_UDP)) != 0) {
+		pr_debug("AT91: PM - Suspend-to-RAM with USB still active\n");
+		return 0;
+	}
+
+#ifdef CONFIG_AT91_PROGRAMMABLE_CLOCKS
+	/* PCK0..PCK3 must be disabled, or configured to use clk32k */
+	for (i = 0; i < 4; i++) {
+		u32 css;
+
+		if ((scsr & (AT91_PMC_PCK0 << i)) == 0)
+			continue;
+
+		css = at91_sys_read(AT91_PMC_PCKR(i)) & AT91_PMC_CSS;
+		if (css != AT91_PMC_CSS_SLOW) {
+			pr_debug("AT91: PM - Suspend-to-RAM with PCK%d src %d\n", i, css);
+			return 0;
+		}
+	}
+#endif
+
+	return 1;
+}
+
+/*
+ * Call this from platform driver suspend() to see how deeply to suspend.
+ * For example, some controllers (like OHCI) need one of the PLL clocks
+ * in order to act as a wakeup source, and those are not available when
+ * going into slow clock mode.
+ *
+ * REVISIT: generalize as clk_will_be_available(clk)?  Other platforms have
+ * the very same problem (but not using at91 main_clk), and it'd be better
+ * to add one generic API rather than lots of platform-specific ones.
+ */
+int at91_suspend_entering_slow_clock(void)
+{
+	return (target_state == PM_SUSPEND_MEM);
+}
+EXPORT_SYMBOL(at91_suspend_entering_slow_clock);
+
+
+static void (*slow_clock)(void);
+
+
+
+static int at91_pm_enter(suspend_state_t state)
+{
+	at91_gpio_suspend();
+	at91_irq_suspend();
+
+	pr_debug("AT91: PM - wake mask %08x, pm state %d\n",
+			/* remember all the always-wake irqs */
+			(at91_sys_read(AT91_PMC_PCSR)
+					| (1 << AT91_ID_FIQ)
+					| (1 << AT91_ID_SYS)
+					| (1 << AT91_ID_IRQ0)
+					| (1 << AT91_ID_IRQ1)
+					| (1 << AT91_ID_IRQ2)
+					| (1 << AT91_ID_IRQ3)
+					| (1 << AT91_ID_IRQ4)
+					| (1 << AT91_ID_IRQ5)
+					| (1 << AT91_ID_IRQ6))
+				& at91_sys_read(AT91_AIC_IMR),
+			state);
+
+	switch (state) {
+		/*
+		 * Suspend-to-RAM is like STANDBY plus slow clock mode, so
+		 * drivers must suspend more deeply:  only the master clock
+		 * controller may be using the main oscillator.
+		 */
+		case PM_SUSPEND_MEM:
+			/*
+			 * Ensure that clocks are in a valid state.
+			 */
+			if (!at91_pm_verify_clocks())
+				goto error;
+
+			/*
+			 * Enter slow clock mode by switching over to clk32k and
+			 * turning off the main oscillator; reverse on wakeup.
+			 */
+			if (slow_clock) {
+				slow_clock();
+				break;
+			} else {
+				/* DEVELOPMENT ONLY */
+				pr_info("AT91: PM - no slow clock mode yet ...\n");
+				/* FALLTHROUGH leaving master clock alone */
+			}
+
+		/*
+		 * STANDBY mode has *all* drivers suspended; ignores irqs not
+		 * marked as 'wakeup' event sources; and reduces DRAM power.
+		 * But otherwise it's identical to PM_SUSPEND_ON:  cpu idle, and
+		 * nothing fancy done with main or cpu clocks.
+		 */
+		case PM_SUSPEND_STANDBY:
+			/*
+			 * NOTE: the Wait-for-Interrupt instruction needs to be
+			 * in icache so the SDRAM stays in self-refresh mode until
+			 * the wakeup IRQ occurs.
+			 */
+			asm("b 1f; .align 5; 1:");
+			asm("mcr p15, 0, r0, c7, c10, 4");	/* drain write buffer */
+			at91_sys_write(AT91_SDRAMC_SRR, 1);	/* self-refresh mode */
+			/* fall though to next state */
+
+		case PM_SUSPEND_ON:
+			asm("mcr p15, 0, r0, c7, c0, 4");	/* wait for interrupt */
+			break;
+
+		default:
+			pr_debug("AT91: PM - bogus suspend state %d\n", state);
+			goto error;
+	}
+
+	pr_debug("AT91: PM - wakeup %08x\n",
+			at91_sys_read(AT91_AIC_IPR) & at91_sys_read(AT91_AIC_IMR));
+
+error:
+	target_state = PM_SUSPEND_ON;
+	at91_irq_resume();
+	at91_gpio_resume();
+	return 0;
+}
+
+
+static struct pm_ops at91_pm_ops ={
+	.pm_disk_mode	= 0,
+	.valid		= at91_pm_valid_state,
+	.prepare	= at91_pm_prepare,
+	.enter		= at91_pm_enter,
+};
+
+static int __init at91_pm_init(void)
+{
+	printk("AT91: Power Management\n");
+
+#ifdef CONFIG_AT91_PM_SLOW_CLOCK
+	/* REVISIT allocations of SRAM should be dynamically managed.
+	 * FIQ handlers and other components will want SRAM/TCM too...
+	 */
+	slow_clock = (void *) (AT91_VA_BASE_SRAM + (3 * SZ_4K));
+	memcpy(slow_clock, at91rm9200_slow_clock, at91rm9200_slow_clock_sz);
+#endif
+
+	/* Disable SDRAM low-power mode.  Cannot be used with self-refresh. */
+	at91_sys_write(AT91_SDRAMC_LPR, 0);
+
+	pm_set_ops(&at91_pm_ops);
+
+	return 0;
+}
+arch_initcall(at91_pm_init);