/*
 * Copyright (c) 2010 Red Hat Inc.
 * Author : Dave Airlie <airlied@redhat.com>
 *
 *
 * Licensed under GPLv2
 *
 * vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs

 Switcher interface - methods require for ATPX and DCM
 - switchto - this throws the output MUX switch
 - discrete_set_power - sets the power state for the discrete card

 GPU driver interface
 - set_gpu_state - this should do the equiv of s/r for the card
                  - this should *not* set the discrete power state
 - switch_check  - check if the device is in a position to switch now
 */

#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/fb.h>

#include <linux/pci.h>
#include <linux/console.h>
#include <linux/vga_switcheroo.h>

#include <linux/vgaarb.h>

struct vga_switcheroo_client {
        struct pci_dev *pdev;
        struct fb_info *fb_info;
        int pwr_state;
        const struct vga_switcheroo_client_ops *ops;
        int id;
        bool active;
        struct list_head list;
};

static DEFINE_MUTEX(vgasr_mutex);

struct vgasr_priv {

        bool active;
        bool delayed_switch_active;
        enum vga_switcheroo_client_id delayed_client_id;

        struct dentry *debugfs_root;
        struct dentry *switch_file;

        int registered_clients;
        struct list_head clients;

        struct vga_switcheroo_handler *handler;
};

#define ID_BIT_AUDIO            0x100
#define client_is_audio(c)      ((c)->id & ID_BIT_AUDIO)
#define client_is_vga(c)        ((c)->id == -1 || !client_is_audio(c))
#define client_id(c)            ((c)->id & ~ID_BIT_AUDIO)

static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);

/* only one switcheroo per system */
static struct vgasr_priv vgasr_priv = {
        .clients = LIST_HEAD_INIT(vgasr_priv.clients),
};

static bool vga_switcheroo_ready(void)
{
        /* we're ready if we get two clients + handler */
        return !vgasr_priv.active &&
               vgasr_priv.registered_clients == 2 && vgasr_priv.handler;
}

static void vga_switcheroo_enable(void)
{
        int ret;
        struct vga_switcheroo_client *client;

        /* call the handler to init */
        if (vgasr_priv.handler->init)
                vgasr_priv.handler->init();

        list_for_each_entry(client, &vgasr_priv.clients, list) {
                if (client->id != -1)
                        continue;
                ret = vgasr_priv.handler->get_client_id(client->pdev);
                if (ret < 0)
                        return;

                client->id = ret;
        }
        vga_switcheroo_debugfs_init(&vgasr_priv);
        vgasr_priv.active = true;
}

int vga_switcheroo_register_handler(struct vga_switcheroo_handler *handler)
{
        mutex_lock(&vgasr_mutex);
        if (vgasr_priv.handler) {
                mutex_unlock(&vgasr_mutex);
                return -EINVAL;
        }

        vgasr_priv.handler = handler;
        if (vga_switcheroo_ready()) {
                printk(KERN_INFO "vga_switcheroo: enabled\n");
                vga_switcheroo_enable();
        }
        mutex_unlock(&vgasr_mutex);
        return 0;
}
EXPORT_SYMBOL(vga_switcheroo_register_handler);

void vga_switcheroo_unregister_handler(void)
{
        mutex_lock(&vgasr_mutex);
        vgasr_priv.handler = NULL;
        if (vgasr_priv.active) {
                pr_info("vga_switcheroo: disabled\n");
                vga_switcheroo_debugfs_fini(&vgasr_priv);
                vgasr_priv.active = false;
        }
        mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_unregister_handler);

static int register_client(struct pci_dev *pdev,
                           const struct vga_switcheroo_client_ops *ops,
                           int id, bool active)
{
        struct vga_switcheroo_client *client;

        client = kzalloc(sizeof(*client), GFP_KERNEL);
        if (!client)
                return -ENOMEM;

        client->pwr_state = VGA_SWITCHEROO_ON;
        client->pdev = pdev;
        client->ops = ops;
        client->id = id;
        client->active = active;

        mutex_lock(&vgasr_mutex);
        list_add_tail(&client->list, &vgasr_priv.clients);
        if (client_is_vga(client))
                vgasr_priv.registered_clients++;

        if (vga_switcheroo_ready()) {
                printk(KERN_INFO "vga_switcheroo: enabled\n");
                vga_switcheroo_enable();
        }
        mutex_unlock(&vgasr_mutex);
        return 0;
}

int vga_switcheroo_register_client(struct pci_dev *pdev,
                                   const struct vga_switcheroo_client_ops *ops)
{
        return register_client(pdev, ops, -1,
                               pdev == vga_default_device());
}
EXPORT_SYMBOL(vga_switcheroo_register_client);

int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
                                         const struct vga_switcheroo_client_ops *ops,
                                         int id, bool active)
{
        return register_client(pdev, ops, id | ID_BIT_AUDIO, active);
}
EXPORT_SYMBOL(vga_switcheroo_register_audio_client);

static struct vga_switcheroo_client *
find_client_from_pci(struct list_head *head, struct pci_dev *pdev)
{
        struct vga_switcheroo_client *client;
        list_for_each_entry(client, head, list)
                if (client->pdev == pdev)
                        return client;
        return NULL;
}

static struct vga_switcheroo_client *
find_client_from_id(struct list_head *head, int client_id)
{
        struct vga_switcheroo_client *client;
        list_for_each_entry(client, head, list)
                if (client->id == client_id)
                        return client;
        return NULL;
}

static struct vga_switcheroo_client *
find_active_client(struct list_head *head)
{
        struct vga_switcheroo_client *client;
        list_for_each_entry(client, head, list)
                if (client->active && client_is_vga(client))
                        return client;
        return NULL;
}

int vga_switcheroo_get_client_state(struct pci_dev *pdev)
{
        struct vga_switcheroo_client *client;

        client = find_client_from_pci(&vgasr_priv.clients, pdev);
        if (!client)
                return VGA_SWITCHEROO_NOT_FOUND;
        if (!vgasr_priv.active)
                return VGA_SWITCHEROO_INIT;
        return client->pwr_state;
}
EXPORT_SYMBOL(vga_switcheroo_get_client_state);

void vga_switcheroo_unregister_client(struct pci_dev *pdev)
{
        struct vga_switcheroo_client *client;

        mutex_lock(&vgasr_mutex);
        client = find_client_from_pci(&vgasr_priv.clients, pdev);
        if (client) {
                if (client_is_vga(client))
                        vgasr_priv.registered_clients--;
                list_del(&client->list);
                kfree(client);
        }
        if (vgasr_priv.active && vgasr_priv.registered_clients < 2) {
                printk(KERN_INFO "vga_switcheroo: disabled\n");
                vga_switcheroo_debugfs_fini(&vgasr_priv);
                vgasr_priv.active = false;
        }
        mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_unregister_client);

void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
                                 struct fb_info *info)
{
        struct vga_switcheroo_client *client;

        mutex_lock(&vgasr_mutex);
        client = find_client_from_pci(&vgasr_priv.clients, pdev);
        if (client)
                client->fb_info = info;
        mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_client_fb_set);

static int vga_switcheroo_show(struct seq_file *m, void *v)
{
        struct vga_switcheroo_client *client;
        int i = 0;
        mutex_lock(&vgasr_mutex);
        list_for_each_entry(client, &vgasr_priv.clients, list) {
                seq_printf(m, "%d:%s%s:%c:%s:%s\n", i,
                           client_id(client) == VGA_SWITCHEROO_DIS ? "DIS" : "IGD",
                           client_is_vga(client) ? "" : "-Audio",
                           client->active ? '+' : ' ',
                           client->pwr_state ? "Pwr" : "Off",
                           pci_name(client->pdev));
                i++;
        }
        mutex_unlock(&vgasr_mutex);
        return 0;
}

static int vga_switcheroo_debugfs_open(struct inode *inode, struct file *file)
{
        return single_open(file, vga_switcheroo_show, NULL);
}

static int vga_switchon(struct vga_switcheroo_client *client)
{
        if (vgasr_priv.handler->power_state)
                vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
        /* call the driver callback to turn on device */
        client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
        client->pwr_state = VGA_SWITCHEROO_ON;
        return 0;
}

static int vga_switchoff(struct vga_switcheroo_client *client)
{
        /* call the driver callback to turn off device */
        client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
        if (vgasr_priv.handler->power_state)
                vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
        client->pwr_state = VGA_SWITCHEROO_OFF;
        return 0;
}

static void set_audio_state(int id, int state)
{
        struct vga_switcheroo_client *client;

        client = find_client_from_id(&vgasr_priv.clients, id | ID_BIT_AUDIO);
        if (client && client->pwr_state != state) {
                client->ops->set_gpu_state(client->pdev, state);
                client->pwr_state = state;
        }
}

/* stage one happens before delay */
static int vga_switchto_stage1(struct vga_switcheroo_client *new_client)
{
        struct vga_switcheroo_client *active;

        active = find_active_client(&vgasr_priv.clients);
        if (!active)
                return 0;

        if (new_client->pwr_state == VGA_SWITCHEROO_OFF)
                vga_switchon(new_client);

        vga_set_default_device(new_client->pdev);
        return 0;
}

/* post delay */
static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
{
        int ret;
        struct vga_switcheroo_client *active;

        active = find_active_client(&vgasr_priv.clients);
        if (!active)
                return 0;

        active->active = false;

        set_audio_state(active->id, VGA_SWITCHEROO_OFF);

        if (new_client->fb_info) {
                struct fb_event event;
                console_lock();
                event.info = new_client->fb_info;
                fb_notifier_call_chain(FB_EVENT_REMAP_ALL_CONSOLE, &event);
                console_unlock();
        }

        ret = vgasr_priv.handler->switchto(new_client->id);
        if (ret)
                return ret;

        if (new_client->ops->reprobe)
                new_client->ops->reprobe(new_client->pdev);

        if (active->pwr_state == VGA_SWITCHEROO_ON)
                vga_switchoff(active);

        set_audio_state(new_client->id, VGA_SWITCHEROO_ON);

        new_client->active = true;
        return 0;
}

static bool check_can_switch(void)
{
        struct vga_switcheroo_client *client;

        list_for_each_entry(client, &vgasr_priv.clients, list) {
                if (!client->ops->can_switch(client->pdev)) {
                        printk(KERN_ERR "vga_switcheroo: client %x refused switch\n", client->id);
                        return false;
                }
        }
        return true;
}

static ssize_t
vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
                             size_t cnt, loff_t *ppos)
{
        char usercmd[64];
        int ret;
        bool delay = false, can_switch;
        bool just_mux = false;
        int client_id = -1;
        struct vga_switcheroo_client *client = NULL;

        if (cnt > 63)
                cnt = 63;

        if (copy_from_user(usercmd, ubuf, cnt))
                return -EFAULT;

        mutex_lock(&vgasr_mutex);

        if (!vgasr_priv.active) {
                cnt = -EINVAL;
                goto out;
        }

        /* pwr off the device not in use */
        if (strncmp(usercmd, "OFF", 3) == 0) {
                list_for_each_entry(client, &vgasr_priv.clients, list) {
                        if (client->active || client_is_audio(client))
                                continue;
                        set_audio_state(client->id, VGA_SWITCHEROO_OFF);
                        if (client->pwr_state == VGA_SWITCHEROO_ON)
                                vga_switchoff(client);
                }
                goto out;
        }
        /* pwr on the device not in use */
        if (strncmp(usercmd, "ON", 2) == 0) {
                list_for_each_entry(client, &vgasr_priv.clients, list) {
                        if (client->active || client_is_audio(client))
                                continue;
                        if (client->pwr_state == VGA_SWITCHEROO_OFF)
                                vga_switchon(client);
                        set_audio_state(client->id, VGA_SWITCHEROO_ON);
                }
                goto out;
        }

        /* request a delayed switch - test can we switch now */
        if (strncmp(usercmd, "DIGD", 4) == 0) {
                client_id = VGA_SWITCHEROO_IGD;
                delay = true;
        }

        if (strncmp(usercmd, "DDIS", 4) == 0) {
                client_id = VGA_SWITCHEROO_DIS;
                delay = true;
        }

        if (strncmp(usercmd, "IGD", 3) == 0)
                client_id = VGA_SWITCHEROO_IGD;

        if (strncmp(usercmd, "DIS", 3) == 0)
                client_id = VGA_SWITCHEROO_DIS;

        if (strncmp(usercmd, "MIGD", 4) == 0) {
                just_mux = true;
                client_id = VGA_SWITCHEROO_IGD;
        }
        if (strncmp(usercmd, "MDIS", 4) == 0) {
                just_mux = true;
                client_id = VGA_SWITCHEROO_DIS;
        }

        if (client_id == -1)
                goto out;
        client = find_client_from_id(&vgasr_priv.clients, client_id);
        if (!client)
                goto out;

        vgasr_priv.delayed_switch_active = false;

        if (just_mux) {
                ret = vgasr_priv.handler->switchto(client_id);
                goto out;
        }

        if (client->active)
                goto out;

        /* okay we want a switch - test if devices are willing to switch */
        can_switch = check_can_switch();

        if (can_switch == false && delay == false)
                goto out;

        if (can_switch) {
                ret = vga_switchto_stage1(client);
                if (ret)
                        printk(KERN_ERR "vga_switcheroo: switching failed stage 1 %d\n", ret);

                ret = vga_switchto_stage2(client);
                if (ret)
                        printk(KERN_ERR "vga_switcheroo: switching failed stage 2 %d\n", ret);

        } else {
                printk(KERN_INFO "vga_switcheroo: setting delayed switch to client %d\n", client->id);
                vgasr_priv.delayed_switch_active = true;
                vgasr_priv.delayed_client_id = client_id;

                ret = vga_switchto_stage1(client);
                if (ret)
                        printk(KERN_ERR "vga_switcheroo: delayed switching stage 1 failed %d\n", ret);
        }

out:
        mutex_unlock(&vgasr_mutex);
        return cnt;
}

static const struct file_operations vga_switcheroo_debugfs_fops = {
        .owner = THIS_MODULE,
        .open = vga_switcheroo_debugfs_open,
        .write = vga_switcheroo_debugfs_write,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
{
        if (priv->switch_file) {
                debugfs_remove(priv->switch_file);
                priv->switch_file = NULL;
        }
        if (priv->debugfs_root) {
                debugfs_remove(priv->debugfs_root);
                priv->debugfs_root = NULL;
        }
}

static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
{
        /* already initialised */
        if (priv->debugfs_root)
                return 0;
        priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);

        if (!priv->debugfs_root) {
                printk(KERN_ERR "vga_switcheroo: Cannot create /sys/kernel/debug/vgaswitcheroo\n");
                goto fail;
        }

        priv->switch_file = debugfs_create_file("switch", 0644,
                                                priv->debugfs_root, NULL, &vga_switcheroo_debugfs_fops);
        if (!priv->switch_file) {
                printk(KERN_ERR "vga_switcheroo: cannot create /sys/kernel/debug/vgaswitcheroo/switch\n");
                goto fail;
        }
        return 0;
fail:
        vga_switcheroo_debugfs_fini(priv);
        return -1;
}

int vga_switcheroo_process_delayed_switch(void)
{
        struct vga_switcheroo_client *client;
        int ret;
        int err = -EINVAL;

        mutex_lock(&vgasr_mutex);
        if (!vgasr_priv.delayed_switch_active)
                goto err;

        printk(KERN_INFO "vga_switcheroo: processing delayed switch to %d\n", vgasr_priv.delayed_client_id);

        client = find_client_from_id(&vgasr_priv.clients,
                                     vgasr_priv.delayed_client_id);
        if (!client || !check_can_switch())
                goto err;

        ret = vga_switchto_stage2(client);
        if (ret)
                printk(KERN_ERR "vga_switcheroo: delayed switching failed stage 2 %d\n", ret);

        vgasr_priv.delayed_switch_active = false;
        err = 0;
err:
        mutex_unlock(&vgasr_mutex);
        return err;
}
EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);