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pm.c

/*
 * arch/arm/mach-at91/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/suspend.h>
#include <linux/sched.h>
#include <linux/proc_fs.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/at91_pmc.h>
#include <asm/arch/at91rm9200_mc.h>
#include <asm/arch/gpio.h>
#include <asm/arch/cpu.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_set_target(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 (cpu_is_at91rm9200()) {
            if ((scsr & (AT91RM9200_PMC_UHP | AT91RM9200_PMC_UDP)) != 0) {
                  pr_debug("AT91: PM - Suspend-to-RAM with USB still active\n");
                  return 0;
            }
      } else if (cpu_is_at91sam9260() || cpu_is_at91sam9261() || cpu_is_at91sam9263()) {
            if ((scsr & (AT91SAM926x_PMC_UHP | AT91SAM926x_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)
                              | (at91_extern_irq))
                        & 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 platform_suspend_ops at91_pm_ops ={
      .valid            = at91_pm_valid_state,
      .set_target = at91_pm_set_target,
      .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);

      suspend_set_ops(&at91_pm_ops);

      return 0;
}
arch_initcall(at91_pm_init);

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