[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>

1 files changed, 225 insertions, 0 deletions

diff --git a/arch/arm/mach-at91rm9200/pm.c b/arch/arm/mach-at91rm9200/pm.c
new file mode 100644
index 000000000000..47e5480feb7e
--- /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);