dpmc.c

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/*
 * Copyright 2008 Analog Devices Inc.
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/cpufreq.h>

#include <asm/delay.h>
#include <asm/dpmc.h>

#define DRIVER_NAME "bfin dpmc"

struct bfin_dpmc_platform_data *pdata;

static void bfin_set_vlev(unsigned int vlev)
{
    unsigned pll_lcnt;

    pll_lcnt = bfin_read_PLL_LOCKCNT();

    bfin_write_PLL_LOCKCNT(1);
    bfin_write_VR_CTL((bfin_read_VR_CTL() & ~VLEV) | vlev);
    bfin_write_PLL_LOCKCNT(pll_lcnt);
}

static unsigned int bfin_get_vlev(unsigned int freq)
{
    int i;

    if (!pdata)
        goto err_out;

    freq >>= 16;

    for (i = 0; i < pdata->tabsize; i++)
        if (freq <= (pdata->tuple_tab[i] & 0xFFFF))
            return pdata->tuple_tab[i] >> 16;

err_out:
    printk(KERN_WARNING "DPMC: No suitable CCLK VDDINT voltage pair found\n");
    return VLEV_120;
}

#ifdef CONFIG_CPU_FREQ
# ifdef CONFIG_SMP
static void bfin_idle_this_cpu(void *info)
{
    unsigned long flags = 0;
    unsigned long iwr0, iwr1, iwr2;
    unsigned int cpu = smp_processor_id();

    local_irq_save_hw(flags);
    bfin_iwr_set_sup0(&iwr0, &iwr1, &iwr2);

    platform_clear_ipi(cpu, IRQ_SUPPLE_0);
    SSYNC();
    asm("IDLE;");
    bfin_iwr_restore(iwr0, iwr1, iwr2);

    local_irq_restore_hw(flags);
}

static void bfin_idle_cpu(void)
{
    smp_call_function(bfin_idle_this_cpu, NULL, 0);
}

static void bfin_wakeup_cpu(void)
{
    unsigned int cpu;
    unsigned int this_cpu = smp_processor_id();
    cpumask_t mask;

    cpumask_copy(&mask, cpu_online_mask);
    cpumask_clear_cpu(this_cpu, &mask);
    for_each_cpu(cpu, &mask)
        platform_send_ipi_cpu(cpu, IRQ_SUPPLE_0);
}

# else
static void bfin_idle_cpu(void) {}
static void bfin_wakeup_cpu(void) {}
# endif

static int
vreg_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
{
    struct cpufreq_freqs *freq = data;

    if (freq->cpu != CPUFREQ_CPU)
        return 0;

    if (val == CPUFREQ_PRECHANGE && freq->old < freq->new) {
        bfin_idle_cpu();
        bfin_set_vlev(bfin_get_vlev(freq->new));
        udelay(pdata->vr_settling_time); /* Wait until Volatge settled */
        bfin_wakeup_cpu();
    } else if (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) {
        bfin_idle_cpu();
        bfin_set_vlev(bfin_get_vlev(freq->new));
        bfin_wakeup_cpu();
    }

    return 0;
}

static struct notifier_block vreg_cpufreq_notifier_block = {
    .notifier_call  = vreg_cpufreq_notifier
};
#endif /* CONFIG_CPU_FREQ */

static int __devinit bfin_dpmc_probe(struct platform_device *pdev)
{
    if (pdev->dev.platform_data)
        pdata = pdev->dev.platform_data;
    else
        return -EINVAL;

    return cpufreq_register_notifier(&vreg_cpufreq_notifier_block,
                     CPUFREQ_TRANSITION_NOTIFIER);
}

static int __devexit bfin_dpmc_remove(struct platform_device *pdev)
{
    pdata = NULL;
    return cpufreq_unregister_notifier(&vreg_cpufreq_notifier_block,
                     CPUFREQ_TRANSITION_NOTIFIER);
}

struct platform_driver bfin_dpmc_device_driver = {
    .probe   = bfin_dpmc_probe,
    .remove  = __devexit_p(bfin_dpmc_remove),
    .driver  = {
        .name = DRIVER_NAME,
    }
};

static int __init bfin_dpmc_init(void)
{
    return platform_driver_register(&bfin_dpmc_device_driver);
}
module_init(bfin_dpmc_init);

static void __exit bfin_dpmc_exit(void)
{
    platform_driver_unregister(&bfin_dpmc_device_driver);
}
module_exit(bfin_dpmc_exit);

MODULE_AUTHOR("Michael Hennerich <[email protected]>");
MODULE_DESCRIPTION("cpu power management driver for Blackfin");
MODULE_LICENSE("GPL");