/*
 * (C) Copyright 2008 Intel Corporation
 * Authors:
 * Andy Henroid <andrew.d.henroid@intel.com>
 * Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 */

/*
 * Save DIMM power on Intel 7300-based platforms when all CPUs/cores
 * are idle, using the DIMM thermal throttling capability.
 *
 * This driver depends on the Intel integrated DMA controller (I/O AT).
 * If the driver for I/O AT (drivers/dma/ioatdma*) is also enabled,
 * this driver should work cooperatively.
 */

/* #define DEBUG */

#include <linux/module.h>
#include <linux/pci.h>
#include <linux/sched.h>
#include <linux/notifier.h>
#include <linux/cpumask.h>
#include <linux/ktime.h>
#include <linux/delay.h>
#include <linux/debugfs.h>
#include <linux/stop_machine.h>
#include <linux/i7300_idle.h>

#include <asm/idle.h>

#include "../dma/ioat/hw.h"
#include "../dma/ioat/registers.h"

#define I7300_IDLE_DRIVER_VERSION       "1.55"
#define I7300_PRINT                     "i7300_idle:"

#define MAX_STOP_RETRIES        10

static int debug;
module_param_named(debug, debug, uint, 0644);
MODULE_PARM_DESC(debug, "Enable debug printks in this driver");

static int forceload;
module_param_named(forceload, forceload, uint, 0644);
MODULE_PARM_DESC(debug, "Enable driver testing on unvalidated i5000");

#define dprintk(fmt, arg...) \
        do { if (debug) printk(KERN_INFO I7300_PRINT fmt, ##arg); } while (0)

/*
 * Value to set THRTLOW to when initiating throttling
 *  0 = No throttling
 *  1 = Throttle when > 4 activations per eval window (Maximum throttling)
 *  2 = Throttle when > 8 activations
 *  168 = Throttle when > 672 activations (Minimum throttling)
 */
#define MAX_THROTTLE_LOW_LIMIT          168
static uint throttle_low_limit = 1;
module_param_named(throttle_low_limit, throttle_low_limit, uint, 0644);
MODULE_PARM_DESC(throttle_low_limit,
                "Value for THRTLOWLM activation field "
                "(0 = disable throttle, 1 = Max throttle, 168 = Min throttle)");

/*
 * simple invocation and duration statistics
 */
static unsigned long total_starts;
static unsigned long total_us;

#ifdef DEBUG
static unsigned long past_skip;
#endif

static struct pci_dev *fbd_dev;

static spinlock_t i7300_idle_lock;
static int i7300_idle_active;

static u8 i7300_idle_thrtctl_saved;
static u8 i7300_idle_thrtlow_saved;
static u32 i7300_idle_mc_saved;

static cpumask_t idle_cpumask;
static ktime_t start_ktime;
static unsigned long avg_idle_us;

static struct dentry *debugfs_dir;

/* Begin: I/O AT Helper routines */

#define IOAT_CHANBASE(ioat_ctl, chan) (ioat_ctl + 0x80 + 0x80 * chan)
/* Snoop control (disable snoops when coherency is not important) */
#define IOAT_DESC_SADDR_SNP_CTL (1UL << 1)
#define IOAT_DESC_DADDR_SNP_CTL (1UL << 2)

static struct pci_dev *ioat_dev;
static struct ioat_dma_descriptor *ioat_desc; /* I/O AT desc & data (1 page) */
static unsigned long ioat_desc_phys;
static u8 *ioat_iomap; /* I/O AT memory-mapped control regs (aka CB_BAR) */
static u8 *ioat_chanbase;

/* Start I/O AT memory copy */
static int i7300_idle_ioat_start(void)
{
        u32 err;
        /* Clear error (due to circular descriptor pointer) */
        err = readl(ioat_chanbase + IOAT_CHANERR_OFFSET);
        if (err)
                writel(err, ioat_chanbase + IOAT_CHANERR_OFFSET);

        writeb(IOAT_CHANCMD_START, ioat_chanbase + IOAT1_CHANCMD_OFFSET);
        return 0;
}

/* Stop I/O AT memory copy */
static void i7300_idle_ioat_stop(void)
{
        int i;
        u64 sts;

        for (i = 0; i < MAX_STOP_RETRIES; i++) {
                writeb(IOAT_CHANCMD_RESET,
                        ioat_chanbase + IOAT1_CHANCMD_OFFSET);

                udelay(10);

                sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
                        IOAT_CHANSTS_STATUS;

                if (sts != IOAT_CHANSTS_ACTIVE)
                        break;

        }

        if (i == MAX_STOP_RETRIES) {
                dprintk("failed to stop I/O AT after %d retries\n",
                        MAX_STOP_RETRIES);
        }
}

/* Test I/O AT by copying 1024 byte from 2k to 1k */
static int __init i7300_idle_ioat_selftest(u8 *ctl,
                struct ioat_dma_descriptor *desc, unsigned long desc_phys)
{
        u64 chan_sts;

        memset(desc, 0, 2048);
        memset((u8 *) desc + 2048, 0xab, 1024);

        desc[0].size = 1024;
        desc[0].ctl = 0;
        desc[0].src_addr = desc_phys + 2048;
        desc[0].dst_addr = desc_phys + 1024;
        desc[0].next = 0;

        writeb(IOAT_CHANCMD_RESET, ioat_chanbase + IOAT1_CHANCMD_OFFSET);
        writeb(IOAT_CHANCMD_START, ioat_chanbase + IOAT1_CHANCMD_OFFSET);

        udelay(1000);

        chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
                        IOAT_CHANSTS_STATUS;

        if (chan_sts != IOAT_CHANSTS_DONE) {
                /* Not complete, reset the channel */
                writeb(IOAT_CHANCMD_RESET,
                       ioat_chanbase + IOAT1_CHANCMD_OFFSET);
                return -1;
        }

        if (*(u32 *) ((u8 *) desc + 3068) != 0xabababab ||
            *(u32 *) ((u8 *) desc + 2044) != 0xabababab) {
                dprintk("Data values src 0x%x, dest 0x%x, memset 0x%x\n",
                        *(u32 *) ((u8 *) desc + 2048),
                        *(u32 *) ((u8 *) desc + 1024),
                        *(u32 *) ((u8 *) desc + 3072));
                return -1;
        }
        return 0;
}

static struct device dummy_dma_dev = {
        .init_name = "fallback device",
        .coherent_dma_mask = DMA_BIT_MASK(64),
        .dma_mask = &dummy_dma_dev.coherent_dma_mask,
};

/* Setup and initialize I/O AT */
/* This driver needs I/O AT as the throttling takes effect only when there is
 * some memory activity. We use I/O AT to set up a dummy copy, while all CPUs
 * go idle and memory is throttled.
 */
static int __init i7300_idle_ioat_init(void)
{
        u8 ver, chan_count, ioat_chan;
        u16 chan_ctl;

        ioat_iomap = (u8 *) ioremap_nocache(pci_resource_start(ioat_dev, 0),
                                            pci_resource_len(ioat_dev, 0));

        if (!ioat_iomap) {
                printk(KERN_ERR I7300_PRINT "failed to map I/O AT registers\n");
                goto err_ret;
        }

        ver = readb(ioat_iomap + IOAT_VER_OFFSET);
        if (ver != IOAT_VER_1_2) {
                printk(KERN_ERR I7300_PRINT "unknown I/O AT version (%u.%u)\n",
                        ver >> 4, ver & 0xf);
                goto err_unmap;
        }

        chan_count = readb(ioat_iomap + IOAT_CHANCNT_OFFSET);
        if (!chan_count) {
                printk(KERN_ERR I7300_PRINT "unexpected # of I/O AT channels "
                        "(%u)\n",
                        chan_count);
                goto err_unmap;
        }

        ioat_chan = chan_count - 1;
        ioat_chanbase = IOAT_CHANBASE(ioat_iomap, ioat_chan);

        chan_ctl = readw(ioat_chanbase + IOAT_CHANCTRL_OFFSET);
        if (chan_ctl & IOAT_CHANCTRL_CHANNEL_IN_USE) {
                printk(KERN_ERR I7300_PRINT "channel %d in use\n", ioat_chan);
                goto err_unmap;
        }

        writew(IOAT_CHANCTRL_CHANNEL_IN_USE,
                ioat_chanbase + IOAT_CHANCTRL_OFFSET);

        ioat_desc = (struct ioat_dma_descriptor *)dma_alloc_coherent(
                        &dummy_dma_dev, 4096,
                        (dma_addr_t *)&ioat_desc_phys, GFP_KERNEL);
        if (!ioat_desc) {
                printk(KERN_ERR I7300_PRINT "failed to allocate I/O AT desc\n");
                goto err_mark_unused;
        }

        writel(ioat_desc_phys & 0xffffffffUL,
               ioat_chanbase + IOAT1_CHAINADDR_OFFSET_LOW);
        writel(ioat_desc_phys >> 32,
               ioat_chanbase + IOAT1_CHAINADDR_OFFSET_HIGH);

        if (i7300_idle_ioat_selftest(ioat_iomap, ioat_desc, ioat_desc_phys)) {
                printk(KERN_ERR I7300_PRINT "I/O AT self-test failed\n");
                goto err_free;
        }

        /* Setup circular I/O AT descriptor chain */
        ioat_desc[0].ctl = IOAT_DESC_SADDR_SNP_CTL | IOAT_DESC_DADDR_SNP_CTL;
        ioat_desc[0].src_addr = ioat_desc_phys + 2048;
        ioat_desc[0].dst_addr = ioat_desc_phys + 3072;
        ioat_desc[0].size = 128;
        ioat_desc[0].next = ioat_desc_phys + sizeof(struct ioat_dma_descriptor);

        ioat_desc[1].ctl = ioat_desc[0].ctl;
        ioat_desc[1].src_addr = ioat_desc[0].src_addr;
        ioat_desc[1].dst_addr = ioat_desc[0].dst_addr;
        ioat_desc[1].size = ioat_desc[0].size;
        ioat_desc[1].next = ioat_desc_phys;

        return 0;

err_free:
        dma_free_coherent(&dummy_dma_dev, 4096, (void *)ioat_desc, 0);
err_mark_unused:
        writew(0, ioat_chanbase + IOAT_CHANCTRL_OFFSET);
err_unmap:
        iounmap(ioat_iomap);
err_ret:
        return -ENODEV;
}

/* Cleanup I/O AT */
static void __exit i7300_idle_ioat_exit(void)
{
        int i;
        u64 chan_sts;

        i7300_idle_ioat_stop();

        /* Wait for a while for the channel to halt before releasing */
        for (i = 0; i < MAX_STOP_RETRIES; i++) {
                writeb(IOAT_CHANCMD_RESET,
                       ioat_chanbase + IOAT1_CHANCMD_OFFSET);

                chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
                        IOAT_CHANSTS_STATUS;

                if (chan_sts != IOAT_CHANSTS_ACTIVE) {
                        writew(0, ioat_chanbase + IOAT_CHANCTRL_OFFSET);
                        break;
                }
                udelay(1000);
        }

        chan_sts = readq(ioat_chanbase + IOAT1_CHANSTS_OFFSET) &
                        IOAT_CHANSTS_STATUS;

        /*
         * We tried to reset multiple times. If IO A/T channel is still active
         * flag an error and return without cleanup. Memory leak is better
         * than random corruption in that extreme error situation.
         */
        if (chan_sts == IOAT_CHANSTS_ACTIVE) {
                printk(KERN_ERR I7300_PRINT "Unable to stop IO A/T channels."
                        " Not freeing resources\n");
                return;
        }

        dma_free_coherent(&dummy_dma_dev, 4096, (void *)ioat_desc, 0);
        iounmap(ioat_iomap);
}

/* End: I/O AT Helper routines */

#define DIMM_THRTLOW 0x64
#define DIMM_THRTCTL 0x67
#define DIMM_THRTCTL_THRMHUNT (1UL << 0)
#define DIMM_MC 0x40
#define DIMM_GTW_MODE (1UL << 17)
#define DIMM_GBLACT 0x60

/*
 * Keep track of an exponential-decaying average of recent idle durations.
 * The latest duration gets DURATION_WEIGHT_PCT percentage weight
 * in this average, with the old average getting the remaining weight.
 *
 * High weights emphasize recent history, low weights include long history.
 */
#define DURATION_WEIGHT_PCT 55

/*
 * When the decaying average of recent durations or the predicted duration
 * of the next timer interrupt is shorter than duration_threshold, the
 * driver will decline to throttle.
 */
#define DURATION_THRESHOLD_US 100


/* Store DIMM thermal throttle configuration */
static int i7300_idle_thrt_save(void)
{
        u32 new_mc_val;
        u8 gblactlm;

        pci_read_config_byte(fbd_dev, DIMM_THRTCTL, &i7300_idle_thrtctl_saved);
        pci_read_config_byte(fbd_dev, DIMM_THRTLOW, &i7300_idle_thrtlow_saved);
        pci_read_config_dword(fbd_dev, DIMM_MC, &i7300_idle_mc_saved);
        /*
         * Make sure we have Global Throttling Window Mode set to have a
         * "short" window. This (mostly) works around an issue where
         * throttling persists until the end of the global throttling window
         * size. On the tested system, this was resulting in a maximum of
         * 64 ms to exit throttling (average 32 ms). The actual numbers
         * depends on system frequencies. Setting the short window reduces
         * this by a factor of 4096.
         *
         * We will only do this only if the system is set for
         * unlimited-activations while in open-loop throttling (i.e., when
         * Global Activation Throttle Limit is zero).
         */
        pci_read_config_byte(fbd_dev, DIMM_GBLACT, &gblactlm);
        dprintk("thrtctl_saved = 0x%02x, thrtlow_saved = 0x%02x\n",
                i7300_idle_thrtctl_saved,
                i7300_idle_thrtlow_saved);
        dprintk("mc_saved = 0x%08x, gblactlm = 0x%02x\n",
                i7300_idle_mc_saved,
                gblactlm);
        if (gblactlm == 0) {
                new_mc_val = i7300_idle_mc_saved | DIMM_GTW_MODE;
                pci_write_config_dword(fbd_dev, DIMM_MC, new_mc_val);
                return 0;
        } else {
                dprintk("could not set GTW_MODE = 1 (OLTT enabled)\n");
                return -ENODEV;
        }
}

/* Restore DIMM thermal throttle configuration */
static void i7300_idle_thrt_restore(void)
{
        pci_write_config_dword(fbd_dev, DIMM_MC, i7300_idle_mc_saved);
        pci_write_config_byte(fbd_dev, DIMM_THRTLOW, i7300_idle_thrtlow_saved);
        pci_write_config_byte(fbd_dev, DIMM_THRTCTL, i7300_idle_thrtctl_saved);
}

/* Enable DIMM thermal throttling */
static void i7300_idle_start(void)
{
        u8 new_ctl;
        u8 limit;

        new_ctl = i7300_idle_thrtctl_saved & ~DIMM_THRTCTL_THRMHUNT;
        pci_write_config_byte(fbd_dev, DIMM_THRTCTL, new_ctl);

        limit = throttle_low_limit;
        if (unlikely(limit > MAX_THROTTLE_LOW_LIMIT))
                limit = MAX_THROTTLE_LOW_LIMIT;

        pci_write_config_byte(fbd_dev, DIMM_THRTLOW, limit);

        new_ctl = i7300_idle_thrtctl_saved | DIMM_THRTCTL_THRMHUNT;
        pci_write_config_byte(fbd_dev, DIMM_THRTCTL, new_ctl);
}

/* Disable DIMM thermal throttling */
static void i7300_idle_stop(void)
{
        u8 new_ctl;
        u8 got_ctl;

        new_ctl = i7300_idle_thrtctl_saved & ~DIMM_THRTCTL_THRMHUNT;
        pci_write_config_byte(fbd_dev, DIMM_THRTCTL, new_ctl);

        pci_write_config_byte(fbd_dev, DIMM_THRTLOW, i7300_idle_thrtlow_saved);
        pci_write_config_byte(fbd_dev, DIMM_THRTCTL, i7300_idle_thrtctl_saved);
        pci_read_config_byte(fbd_dev, DIMM_THRTCTL, &got_ctl);
        WARN_ON_ONCE(got_ctl != i7300_idle_thrtctl_saved);
}


/*
 * i7300_avg_duration_check()
 * return 0 if the decaying average of recent idle durations is
 * more than DURATION_THRESHOLD_US
 */
static int i7300_avg_duration_check(void)
{
        if (avg_idle_us >= DURATION_THRESHOLD_US)
                return 0;

#ifdef DEBUG
        past_skip++;
#endif
        return 1;
}

/* Idle notifier to look at idle CPUs */
static int i7300_idle_notifier(struct notifier_block *nb, unsigned long val,
                                void *data)
{
        unsigned long flags;
        ktime_t now_ktime;
        static ktime_t idle_begin_time;
        static int time_init = 1;

        if (!throttle_low_limit)
                return 0;

        if (unlikely(time_init)) {
                time_init = 0;
                idle_begin_time = ktime_get();
        }

        spin_lock_irqsave(&i7300_idle_lock, flags);
        if (val == IDLE_START) {

                cpu_set(smp_processor_id(), idle_cpumask);

                if (cpus_weight(idle_cpumask) != num_online_cpus())
                        goto end;

                now_ktime = ktime_get();
                idle_begin_time = now_ktime;

                if (i7300_avg_duration_check())
                        goto end;

                i7300_idle_active = 1;
                total_starts++;
                start_ktime = now_ktime;

                i7300_idle_start();
                i7300_idle_ioat_start();

        } else if (val == IDLE_END) {
                cpu_clear(smp_processor_id(), idle_cpumask);
                if (cpus_weight(idle_cpumask) == (num_online_cpus() - 1)) {
                        /* First CPU coming out of idle */
                        u64 idle_duration_us;

                        now_ktime = ktime_get();

                        idle_duration_us = ktime_to_us(ktime_sub
                                                (now_ktime, idle_begin_time));

                        avg_idle_us =
                                ((100 - DURATION_WEIGHT_PCT) * avg_idle_us +
                                 DURATION_WEIGHT_PCT * idle_duration_us) / 100;

                        if (i7300_idle_active) {
                                ktime_t idle_ktime;

                                idle_ktime = ktime_sub(now_ktime, start_ktime);
                                total_us += ktime_to_us(idle_ktime);

                                i7300_idle_ioat_stop();
                                i7300_idle_stop();
                                i7300_idle_active = 0;
                        }
                }
        }
end:
        spin_unlock_irqrestore(&i7300_idle_lock, flags);
        return 0;
}

static struct notifier_block i7300_idle_nb = {
        .notifier_call = i7300_idle_notifier,
};

MODULE_DEVICE_TABLE(pci, pci_tbl);

int stats_open_generic(struct inode *inode, struct file *fp)
{
        fp->private_data = inode->i_private;
        return 0;
}

static ssize_t stats_read_ul(struct file *fp, char __user *ubuf, size_t count,
                                loff_t *off)
{
        unsigned long *p = fp->private_data;
        char buf[32];
        int len;

        len = snprintf(buf, 32, "%lu\n", *p);
        return simple_read_from_buffer(ubuf, count, off, buf, len);
}

static const struct file_operations idle_fops = {
        .open   = stats_open_generic,
        .read   = stats_read_ul,
};

struct debugfs_file_info {
        void *ptr;
        char name[32];
        struct dentry *file;
} debugfs_file_list[] = {
                                {&total_starts, "total_starts", NULL},
                                {&total_us, "total_us", NULL},
#ifdef DEBUG
                                {&past_skip, "past_skip", NULL},
#endif
                                {NULL, "", NULL}
                        };

static int __init i7300_idle_init(void)
{
        spin_lock_init(&i7300_idle_lock);
        cpus_clear(idle_cpumask);
        total_us = 0;

        if (i7300_idle_platform_probe(&fbd_dev, &ioat_dev, forceload))
                return -ENODEV;

        if (i7300_idle_thrt_save())
                return -ENODEV;

        if (i7300_idle_ioat_init())
                return -ENODEV;

        debugfs_dir = debugfs_create_dir("i7300_idle", NULL);
        if (debugfs_dir) {
                int i = 0;

                while (debugfs_file_list[i].ptr != NULL) {
                        debugfs_file_list[i].file = debugfs_create_file(
                                        debugfs_file_list[i].name,
                                        S_IRUSR,
                                        debugfs_dir,
                                        debugfs_file_list[i].ptr,
                                        &idle_fops);
                        i++;
                }
        }

        idle_notifier_register(&i7300_idle_nb);

        printk(KERN_INFO "i7300_idle: loaded v%s\n", I7300_IDLE_DRIVER_VERSION);
        return 0;
}

static void __exit i7300_idle_exit(void)
{
        idle_notifier_unregister(&i7300_idle_nb);

        if (debugfs_dir) {
                int i = 0;

                while (debugfs_file_list[i].file != NULL) {
                        debugfs_remove(debugfs_file_list[i].file);
                        i++;
                }

                debugfs_remove(debugfs_dir);
        }
        i7300_idle_thrt_restore();
        i7300_idle_ioat_exit();
}

module_init(i7300_idle_init);
module_exit(i7300_idle_exit);

MODULE_AUTHOR("Andy Henroid <andrew.d.henroid@intel.com>");
MODULE_DESCRIPTION("Intel Chipset DIMM Idle Power Saving Driver v"
                        I7300_IDLE_DRIVER_VERSION);
MODULE_LICENSE("GPL");