// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2012, Microsoft Corporation.
 *
 * Author:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 */

/*
 * Hyper-V Synthetic Video Frame Buffer Driver
 *
 * This is the driver for the Hyper-V Synthetic Video, which supports
 * screen resolution up to Full HD 1920x1080 with 32 bit color on Windows
 * Server 2012, and 1600x1200 with 16 bit color on Windows Server 2008 R2
 * or earlier.
 *
 * It also solves the double mouse cursor issue of the emulated video mode.
 *
 * The default screen resolution is 1152x864, which may be changed by a
 * kernel parameter:
 *     video=hyperv_fb:<width>x<height>
 *     For example: video=hyperv_fb:1280x1024
 *
 * Portrait orientation is also supported:
 *     For example: video=hyperv_fb:864x1152
 *
 * When a Windows 10 RS5+ host is used, the virtual machine screen
 * resolution is obtained from the host. The "video=hyperv_fb" option is
 * not needed, but still can be used to overwrite what the host specifies.
 * The VM resolution on the host could be set by executing the powershell
 * "set-vmvideo" command. For example
 *     set-vmvideo -vmname name -horizontalresolution:1920 \
 * -verticalresolution:1200 -resolutiontype single
 *
 * Gen 1 VMs also support direct using VM's physical memory for framebuffer.
 * It could improve the efficiency and performance for framebuffer and VM.
 * This requires to allocate contiguous physical memory from Linux kernel's
 * CMA memory allocator. To enable this, supply a kernel parameter to give
 * enough memory space to CMA allocator for framebuffer. For example:
 *    cma=130m
 * This gives 130MB memory to CMA allocator that can be allocated to
 * framebuffer. For reference, 8K resolution (7680x4320) takes about
 * 127MB memory.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/fb.h>
#include <linux/pci.h>
#include <linux/efi.h>
#include <linux/console.h>

#include <linux/hyperv.h>


/* Hyper-V Synthetic Video Protocol definitions and structures */
#define MAX_VMBUS_PKT_SIZE 0x4000

#define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
#define SYNTHVID_VERSION_WIN7 SYNTHVID_VERSION(3, 0)
#define SYNTHVID_VERSION_WIN8 SYNTHVID_VERSION(3, 2)
#define SYNTHVID_VERSION_WIN10 SYNTHVID_VERSION(3, 5)

#define SYNTHVID_VER_GET_MAJOR(ver) (ver & 0x0000ffff)
#define SYNTHVID_VER_GET_MINOR(ver) ((ver & 0xffff0000) >> 16)

#define SYNTHVID_DEPTH_WIN7 16
#define SYNTHVID_DEPTH_WIN8 32

#define SYNTHVID_FB_SIZE_WIN7 (4 * 1024 * 1024)
#define SYNTHVID_WIDTH_MAX_WIN7 1600
#define SYNTHVID_HEIGHT_MAX_WIN7 1200

#define SYNTHVID_FB_SIZE_WIN8 (8 * 1024 * 1024)

#define PCI_VENDOR_ID_MICROSOFT 0x1414
#define PCI_DEVICE_ID_HYPERV_VIDEO 0x5353


enum pipe_msg_type {
        PIPE_MSG_INVALID,
        PIPE_MSG_DATA,
        PIPE_MSG_MAX
};

struct pipe_msg_hdr {
        u32 type;
        u32 size; /* size of message after this field */
} __packed;


enum synthvid_msg_type {
        SYNTHVID_ERROR                  = 0,
        SYNTHVID_VERSION_REQUEST        = 1,
        SYNTHVID_VERSION_RESPONSE       = 2,
        SYNTHVID_VRAM_LOCATION          = 3,
        SYNTHVID_VRAM_LOCATION_ACK      = 4,
        SYNTHVID_SITUATION_UPDATE       = 5,
        SYNTHVID_SITUATION_UPDATE_ACK   = 6,
        SYNTHVID_POINTER_POSITION       = 7,
        SYNTHVID_POINTER_SHAPE          = 8,
        SYNTHVID_FEATURE_CHANGE         = 9,
        SYNTHVID_DIRT                   = 10,
        SYNTHVID_RESOLUTION_REQUEST     = 13,
        SYNTHVID_RESOLUTION_RESPONSE    = 14,

        SYNTHVID_MAX                    = 15
};

#define         SYNTHVID_EDID_BLOCK_SIZE        128
#define         SYNTHVID_MAX_RESOLUTION_COUNT   64

struct hvd_screen_info {
        u16 width;
        u16 height;
} __packed;

struct synthvid_msg_hdr {
        u32 type;
        u32 size;  /* size of this header + payload after this field*/
} __packed;

struct synthvid_version_req {
        u32 version;
} __packed;

struct synthvid_version_resp {
        u32 version;
        u8 is_accepted;
        u8 max_video_outputs;
} __packed;

struct synthvid_supported_resolution_req {
        u8 maximum_resolution_count;
} __packed;

struct synthvid_supported_resolution_resp {
        u8 edid_block[SYNTHVID_EDID_BLOCK_SIZE];
        u8 resolution_count;
        u8 default_resolution_index;
        u8 is_standard;
        struct hvd_screen_info
                supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT];
} __packed;

struct synthvid_vram_location {
        u64 user_ctx;
        u8 is_vram_gpa_specified;
        u64 vram_gpa;
} __packed;

struct synthvid_vram_location_ack {
        u64 user_ctx;
} __packed;

struct video_output_situation {
        u8 active;
        u32 vram_offset;
        u8 depth_bits;
        u32 width_pixels;
        u32 height_pixels;
        u32 pitch_bytes;
} __packed;

struct synthvid_situation_update {
        u64 user_ctx;
        u8 video_output_count;
        struct video_output_situation video_output[1];
} __packed;

struct synthvid_situation_update_ack {
        u64 user_ctx;
} __packed;

struct synthvid_pointer_position {
        u8 is_visible;
        u8 video_output;
        s32 image_x;
        s32 image_y;
} __packed;


#define CURSOR_MAX_X 96
#define CURSOR_MAX_Y 96
#define CURSOR_ARGB_PIXEL_SIZE 4
#define CURSOR_MAX_SIZE (CURSOR_MAX_X * CURSOR_MAX_Y * CURSOR_ARGB_PIXEL_SIZE)
#define CURSOR_COMPLETE (-1)

struct synthvid_pointer_shape {
        u8 part_idx;
        u8 is_argb;
        u32 width; /* CURSOR_MAX_X at most */
        u32 height; /* CURSOR_MAX_Y at most */
        u32 hot_x; /* hotspot relative to upper-left of pointer image */
        u32 hot_y;
        u8 data[4];
} __packed;

struct synthvid_feature_change {
        u8 is_dirt_needed;
        u8 is_ptr_pos_needed;
        u8 is_ptr_shape_needed;
        u8 is_situ_needed;
} __packed;

struct rect {
        s32 x1, y1; /* top left corner */
        s32 x2, y2; /* bottom right corner, exclusive */
} __packed;

struct synthvid_dirt {
        u8 video_output;
        u8 dirt_count;
        struct rect rect[1];
} __packed;

struct synthvid_msg {
        struct pipe_msg_hdr pipe_hdr;
        struct synthvid_msg_hdr vid_hdr;
        union {
                struct synthvid_version_req ver_req;
                struct synthvid_version_resp ver_resp;
                struct synthvid_vram_location vram;
                struct synthvid_vram_location_ack vram_ack;
                struct synthvid_situation_update situ;
                struct synthvid_situation_update_ack situ_ack;
                struct synthvid_pointer_position ptr_pos;
                struct synthvid_pointer_shape ptr_shape;
                struct synthvid_feature_change feature_chg;
                struct synthvid_dirt dirt;
                struct synthvid_supported_resolution_req resolution_req;
                struct synthvid_supported_resolution_resp resolution_resp;
        };
} __packed;


/* FB driver definitions and structures */
#define HVFB_WIDTH 1152 /* default screen width */
#define HVFB_HEIGHT 864 /* default screen height */
#define HVFB_WIDTH_MIN 640
#define HVFB_HEIGHT_MIN 480

#define RING_BUFSIZE (256 * 1024)
#define VSP_TIMEOUT (10 * HZ)
#define HVFB_UPDATE_DELAY (HZ / 20)
#define HVFB_ONDEMAND_THROTTLE (HZ / 20)

struct hvfb_par {
        struct fb_info *info;
        struct resource *mem;
        bool fb_ready; /* fb device is ready */
        struct completion wait;
        u32 synthvid_version;

        struct delayed_work dwork;
        bool update;
        bool update_saved; /* The value of 'update' before hibernation */

        u32 pseudo_palette[16];
        u8 init_buf[MAX_VMBUS_PKT_SIZE];
        u8 recv_buf[MAX_VMBUS_PKT_SIZE];

        /* If true, the VSC notifies the VSP on every framebuffer change */
        bool synchronous_fb;

        /* If true, need to copy from deferred IO mem to framebuffer mem */
        bool need_docopy;

        struct notifier_block hvfb_panic_nb;

        /* Memory for deferred IO and frame buffer itself */
        unsigned char *dio_vp;
        unsigned char *mmio_vp;
        phys_addr_t mmio_pp;

        /* Dirty rectangle, protected by delayed_refresh_lock */
        int x1, y1, x2, y2;
        bool delayed_refresh;
        spinlock_t delayed_refresh_lock;
};

static uint screen_width = HVFB_WIDTH;
static uint screen_height = HVFB_HEIGHT;
static uint screen_width_max = HVFB_WIDTH;
static uint screen_height_max = HVFB_HEIGHT;
static uint screen_depth;
static uint screen_fb_size;
static uint dio_fb_size; /* FB size for deferred IO */

/* Send message to Hyper-V host */
static inline int synthvid_send(struct hv_device *hdev,
                                struct synthvid_msg *msg)
{
        static atomic64_t request_id = ATOMIC64_INIT(0);
        int ret;

        msg->pipe_hdr.type = PIPE_MSG_DATA;
        msg->pipe_hdr.size = msg->vid_hdr.size;

        ret = vmbus_sendpacket(hdev->channel, msg,
                               msg->vid_hdr.size + sizeof(struct pipe_msg_hdr),
                               atomic64_inc_return(&request_id),
                               VM_PKT_DATA_INBAND, 0);

        if (ret)
                pr_err("Unable to send packet via vmbus\n");

        return ret;
}


/* Send screen resolution info to host */
static int synthvid_send_situ(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct synthvid_msg msg;

        if (!info)
                return -ENODEV;

        memset(&msg, 0, sizeof(struct synthvid_msg));

        msg.vid_hdr.type = SYNTHVID_SITUATION_UPDATE;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_situation_update);
        msg.situ.user_ctx = 0;
        msg.situ.video_output_count = 1;
        msg.situ.video_output[0].active = 1;
        msg.situ.video_output[0].vram_offset = 0;
        msg.situ.video_output[0].depth_bits = info->var.bits_per_pixel;
        msg.situ.video_output[0].width_pixels = info->var.xres;
        msg.situ.video_output[0].height_pixels = info->var.yres;
        msg.situ.video_output[0].pitch_bytes = info->fix.line_length;

        synthvid_send(hdev, &msg);

        return 0;
}

/* Send mouse pointer info to host */
static int synthvid_send_ptr(struct hv_device *hdev)
{
        struct synthvid_msg msg;

        memset(&msg, 0, sizeof(struct synthvid_msg));
        msg.vid_hdr.type = SYNTHVID_POINTER_POSITION;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_pointer_position);
        msg.ptr_pos.is_visible = 1;
        msg.ptr_pos.video_output = 0;
        msg.ptr_pos.image_x = 0;
        msg.ptr_pos.image_y = 0;
        synthvid_send(hdev, &msg);

        memset(&msg, 0, sizeof(struct synthvid_msg));
        msg.vid_hdr.type = SYNTHVID_POINTER_SHAPE;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_pointer_shape);
        msg.ptr_shape.part_idx = CURSOR_COMPLETE;
        msg.ptr_shape.is_argb = 1;
        msg.ptr_shape.width = 1;
        msg.ptr_shape.height = 1;
        msg.ptr_shape.hot_x = 0;
        msg.ptr_shape.hot_y = 0;
        msg.ptr_shape.data[0] = 0;
        msg.ptr_shape.data[1] = 1;
        msg.ptr_shape.data[2] = 1;
        msg.ptr_shape.data[3] = 1;
        synthvid_send(hdev, &msg);

        return 0;
}

/* Send updated screen area (dirty rectangle) location to host */
static int
synthvid_update(struct fb_info *info, int x1, int y1, int x2, int y2)
{
        struct hv_device *hdev = device_to_hv_device(info->device);
        struct synthvid_msg msg;

        memset(&msg, 0, sizeof(struct synthvid_msg));
        if (x2 == INT_MAX)
                x2 = info->var.xres;
        if (y2 == INT_MAX)
                y2 = info->var.yres;

        msg.vid_hdr.type = SYNTHVID_DIRT;
        msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_dirt);
        msg.dirt.video_output = 0;
        msg.dirt.dirt_count = 1;
        msg.dirt.rect[0].x1 = (x1 > x2) ? 0 : x1;
        msg.dirt.rect[0].y1 = (y1 > y2) ? 0 : y1;
        msg.dirt.rect[0].x2 =
                (x2 < x1 || x2 > info->var.xres) ? info->var.xres : x2;
        msg.dirt.rect[0].y2 =
                (y2 < y1 || y2 > info->var.yres) ? info->var.yres : y2;

        synthvid_send(hdev, &msg);

        return 0;
}

static void hvfb_docopy(struct hvfb_par *par,
                        unsigned long offset,
                        unsigned long size)
{
        if (!par || !par->mmio_vp || !par->dio_vp || !par->fb_ready ||
            size == 0 || offset >= dio_fb_size)
                return;

        if (offset + size > dio_fb_size)
                size = dio_fb_size - offset;

        memcpy(par->mmio_vp + offset, par->dio_vp + offset, size);
}

/* Deferred IO callback */
static void synthvid_deferred_io(struct fb_info *p,
                                 struct list_head *pagelist)
{
        struct hvfb_par *par = p->par;
        struct page *page;
        unsigned long start, end;
        int y1, y2, miny, maxy;

        miny = INT_MAX;
        maxy = 0;

        /*
         * Merge dirty pages. It is possible that last page cross
         * over the end of frame buffer row yres. This is taken care of
         * in synthvid_update function by clamping the y2
         * value to yres.
         */
        list_for_each_entry(page, pagelist, lru) {
                start = page->index << PAGE_SHIFT;
                end = start + PAGE_SIZE - 1;
                y1 = start / p->fix.line_length;
                y2 = end / p->fix.line_length;
                miny = min_t(int, miny, y1);
                maxy = max_t(int, maxy, y2);

                /* Copy from dio space to mmio address */
                if (par->fb_ready && par->need_docopy)
                        hvfb_docopy(par, start, PAGE_SIZE);
        }

        if (par->fb_ready && par->update)
                synthvid_update(p, 0, miny, p->var.xres, maxy + 1);
}

static struct fb_deferred_io synthvid_defio = {
        .delay          = HZ / 20,
        .deferred_io    = synthvid_deferred_io,
};

/*
 * Actions on received messages from host:
 * Complete the wait event.
 * Or, reply with screen and cursor info.
 */
static void synthvid_recv_sub(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par;
        struct synthvid_msg *msg;

        if (!info)
                return;

        par = info->par;
        msg = (struct synthvid_msg *)par->recv_buf;

        /* Complete the wait event */
        if (msg->vid_hdr.type == SYNTHVID_VERSION_RESPONSE ||
            msg->vid_hdr.type == SYNTHVID_RESOLUTION_RESPONSE ||
            msg->vid_hdr.type == SYNTHVID_VRAM_LOCATION_ACK) {
                memcpy(par->init_buf, msg, MAX_VMBUS_PKT_SIZE);
                complete(&par->wait);
                return;
        }

        /* Reply with screen and cursor info */
        if (msg->vid_hdr.type == SYNTHVID_FEATURE_CHANGE) {
                if (par->fb_ready) {
                        synthvid_send_ptr(hdev);
                        synthvid_send_situ(hdev);
                }

                par->update = msg->feature_chg.is_dirt_needed;
                if (par->update)
                        schedule_delayed_work(&par->dwork, HVFB_UPDATE_DELAY);
        }
}

/* Receive callback for messages from the host */
static void synthvid_receive(void *ctx)
{
        struct hv_device *hdev = ctx;
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par;
        struct synthvid_msg *recv_buf;
        u32 bytes_recvd;
        u64 req_id;
        int ret;

        if (!info)
                return;

        par = info->par;
        recv_buf = (struct synthvid_msg *)par->recv_buf;

        do {
                ret = vmbus_recvpacket(hdev->channel, recv_buf,
                                       MAX_VMBUS_PKT_SIZE,
                                       &bytes_recvd, &req_id);
                if (bytes_recvd > 0 &&
                    recv_buf->pipe_hdr.type == PIPE_MSG_DATA)
                        synthvid_recv_sub(hdev);
        } while (bytes_recvd > 0 && ret == 0);
}

/* Check if the ver1 version is equal or greater than ver2 */
static inline bool synthvid_ver_ge(u32 ver1, u32 ver2)
{
        if (SYNTHVID_VER_GET_MAJOR(ver1) > SYNTHVID_VER_GET_MAJOR(ver2) ||
            (SYNTHVID_VER_GET_MAJOR(ver1) == SYNTHVID_VER_GET_MAJOR(ver2) &&
             SYNTHVID_VER_GET_MINOR(ver1) >= SYNTHVID_VER_GET_MINOR(ver2)))
                return true;

        return false;
}

/* Check synthetic video protocol version with the host */
static int synthvid_negotiate_ver(struct hv_device *hdev, u32 ver)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        struct synthvid_msg *msg = (struct synthvid_msg *)par->init_buf;
        int ret = 0;
        unsigned long t;

        memset(msg, 0, sizeof(struct synthvid_msg));
        msg->vid_hdr.type = SYNTHVID_VERSION_REQUEST;
        msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_version_req);
        msg->ver_req.version = ver;
        synthvid_send(hdev, msg);

        t = wait_for_completion_timeout(&par->wait, VSP_TIMEOUT);
        if (!t) {
                pr_err("Time out on waiting version response\n");
                ret = -ETIMEDOUT;
                goto out;
        }
        if (!msg->ver_resp.is_accepted) {
                ret = -ENODEV;
                goto out;
        }

        par->synthvid_version = ver;
        pr_info("Synthvid Version major %d, minor %d\n",
                SYNTHVID_VER_GET_MAJOR(ver), SYNTHVID_VER_GET_MINOR(ver));

out:
        return ret;
}

/* Get current resolution from the host */
static int synthvid_get_supported_resolution(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        struct synthvid_msg *msg = (struct synthvid_msg *)par->init_buf;
        int ret = 0;
        unsigned long t;
        u8 index;
        int i;

        memset(msg, 0, sizeof(struct synthvid_msg));
        msg->vid_hdr.type = SYNTHVID_RESOLUTION_REQUEST;
        msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_supported_resolution_req);

        msg->resolution_req.maximum_resolution_count =
                SYNTHVID_MAX_RESOLUTION_COUNT;
        synthvid_send(hdev, msg);

        t = wait_for_completion_timeout(&par->wait, VSP_TIMEOUT);
        if (!t) {
                pr_err("Time out on waiting resolution response\n");
                ret = -ETIMEDOUT;
                goto out;
        }

        if (msg->resolution_resp.resolution_count == 0) {
                pr_err("No supported resolutions\n");
                ret = -ENODEV;
                goto out;
        }

        index = msg->resolution_resp.default_resolution_index;
        if (index >= msg->resolution_resp.resolution_count) {
                pr_err("Invalid resolution index: %d\n", index);
                ret = -ENODEV;
                goto out;
        }

        for (i = 0; i < msg->resolution_resp.resolution_count; i++) {
                screen_width_max = max_t(unsigned int, screen_width_max,
                    msg->resolution_resp.supported_resolution[i].width);
                screen_height_max = max_t(unsigned int, screen_height_max,
                    msg->resolution_resp.supported_resolution[i].height);
        }

        screen_width =
                msg->resolution_resp.supported_resolution[index].width;
        screen_height =
                msg->resolution_resp.supported_resolution[index].height;

out:
        return ret;
}

/* Connect to VSP (Virtual Service Provider) on host */
static int synthvid_connect_vsp(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        int ret;

        ret = vmbus_open(hdev->channel, RING_BUFSIZE, RING_BUFSIZE,
                         NULL, 0, synthvid_receive, hdev);
        if (ret) {
                pr_err("Unable to open vmbus channel\n");
                return ret;
        }

        /* Negotiate the protocol version with host */
        switch (vmbus_proto_version) {
        case VERSION_WIN10:
        case VERSION_WIN10_V5:
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN10);
                if (!ret)
                        break;
                fallthrough;
        case VERSION_WIN8:
        case VERSION_WIN8_1:
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN8);
                if (!ret)
                        break;
                fallthrough;
        case VERSION_WS2008:
        case VERSION_WIN7:
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN7);
                break;
        default:
                ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN10);
                break;
        }

        if (ret) {
                pr_err("Synthetic video device version not accepted\n");
                goto error;
        }

        if (par->synthvid_version == SYNTHVID_VERSION_WIN7)
                screen_depth = SYNTHVID_DEPTH_WIN7;
        else
                screen_depth = SYNTHVID_DEPTH_WIN8;

        if (synthvid_ver_ge(par->synthvid_version, SYNTHVID_VERSION_WIN10)) {
                ret = synthvid_get_supported_resolution(hdev);
                if (ret)
                        pr_info("Failed to get supported resolution from host, use default\n");
        }

        screen_fb_size = hdev->channel->offermsg.offer.
                                mmio_megabytes * 1024 * 1024;

        return 0;

error:
        vmbus_close(hdev->channel);
        return ret;
}

/* Send VRAM and Situation messages to the host */
static int synthvid_send_config(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        struct synthvid_msg *msg = (struct synthvid_msg *)par->init_buf;
        int ret = 0;
        unsigned long t;

        /* Send VRAM location */
        memset(msg, 0, sizeof(struct synthvid_msg));
        msg->vid_hdr.type = SYNTHVID_VRAM_LOCATION;
        msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
                sizeof(struct synthvid_vram_location);
        msg->vram.user_ctx = msg->vram.vram_gpa = par->mmio_pp;
        msg->vram.is_vram_gpa_specified = 1;
        synthvid_send(hdev, msg);

        t = wait_for_completion_timeout(&par->wait, VSP_TIMEOUT);
        if (!t) {
                pr_err("Time out on waiting vram location ack\n");
                ret = -ETIMEDOUT;
                goto out;
        }
        if (msg->vram_ack.user_ctx != par->mmio_pp) {
                pr_err("Unable to set VRAM location\n");
                ret = -ENODEV;
                goto out;
        }

        /* Send pointer and situation update */
        synthvid_send_ptr(hdev);
        synthvid_send_situ(hdev);

out:
        return ret;
}


/*
 * Delayed work callback:
 * It is scheduled to call whenever update request is received and it has
 * not been called in last HVFB_ONDEMAND_THROTTLE time interval.
 */
static void hvfb_update_work(struct work_struct *w)
{
        struct hvfb_par *par = container_of(w, struct hvfb_par, dwork.work);
        struct fb_info *info = par->info;
        unsigned long flags;
        int x1, x2, y1, y2;
        int j;

        spin_lock_irqsave(&par->delayed_refresh_lock, flags);
        /* Reset the request flag */
        par->delayed_refresh = false;

        /* Store the dirty rectangle to local variables */
        x1 = par->x1;
        x2 = par->x2;
        y1 = par->y1;
        y2 = par->y2;

        /* Clear dirty rectangle */
        par->x1 = par->y1 = INT_MAX;
        par->x2 = par->y2 = 0;

        spin_unlock_irqrestore(&par->delayed_refresh_lock, flags);

        if (x1 > info->var.xres || x2 > info->var.xres ||
            y1 > info->var.yres || y2 > info->var.yres || x2 <= x1)
                return;

        /* Copy the dirty rectangle to frame buffer memory */
        if (par->need_docopy)
                for (j = y1; j < y2; j++)
                        hvfb_docopy(par,
                                    j * info->fix.line_length +
                                    (x1 * screen_depth / 8),
                                    (x2 - x1) * screen_depth / 8);

        /* Refresh */
        if (par->fb_ready && par->update)
                synthvid_update(info, x1, y1, x2, y2);
}

/*
 * Control the on-demand refresh frequency. It schedules a delayed
 * screen update if it has not yet.
 */
static void hvfb_ondemand_refresh_throttle(struct hvfb_par *par,
                                           int x1, int y1, int w, int h)
{
        unsigned long flags;
        int x2 = x1 + w;
        int y2 = y1 + h;

        spin_lock_irqsave(&par->delayed_refresh_lock, flags);

        /* Merge dirty rectangle */
        par->x1 = min_t(int, par->x1, x1);
        par->y1 = min_t(int, par->y1, y1);
        par->x2 = max_t(int, par->x2, x2);
        par->y2 = max_t(int, par->y2, y2);

        /* Schedule a delayed screen update if not yet */
        if (par->delayed_refresh == false) {
                schedule_delayed_work(&par->dwork,
                                      HVFB_ONDEMAND_THROTTLE);
                par->delayed_refresh = true;
        }

        spin_unlock_irqrestore(&par->delayed_refresh_lock, flags);
}

static int hvfb_on_panic(struct notifier_block *nb,
                         unsigned long e, void *p)
{
        struct hvfb_par *par;
        struct fb_info *info;

        par = container_of(nb, struct hvfb_par, hvfb_panic_nb);
        par->synchronous_fb = true;
        info = par->info;
        if (par->need_docopy)
                hvfb_docopy(par, 0, dio_fb_size);
        synthvid_update(info, 0, 0, INT_MAX, INT_MAX);

        return NOTIFY_DONE;
}

/* Framebuffer operation handlers */

static int hvfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
        if (var->xres < HVFB_WIDTH_MIN || var->yres < HVFB_HEIGHT_MIN ||
            var->xres > screen_width || var->yres >  screen_height ||
            var->bits_per_pixel != screen_depth)
                return -EINVAL;

        var->xres_virtual = var->xres;
        var->yres_virtual = var->yres;

        return 0;
}

static int hvfb_set_par(struct fb_info *info)
{
        struct hv_device *hdev = device_to_hv_device(info->device);

        return synthvid_send_situ(hdev);
}


static inline u32 chan_to_field(u32 chan, struct fb_bitfield *bf)
{
        return ((chan & 0xffff) >> (16 - bf->length)) << bf->offset;
}

static int hvfb_setcolreg(unsigned regno, unsigned red, unsigned green,
                          unsigned blue, unsigned transp, struct fb_info *info)
{
        u32 *pal = info->pseudo_palette;

        if (regno > 15)
                return -EINVAL;

        pal[regno] = chan_to_field(red, &info->var.red)
                | chan_to_field(green, &info->var.green)
                | chan_to_field(blue, &info->var.blue)
                | chan_to_field(transp, &info->var.transp);

        return 0;
}

static int hvfb_blank(int blank, struct fb_info *info)
{
        return 1;       /* get fb_blank to set the colormap to all black */
}

static void hvfb_cfb_fillrect(struct fb_info *p,
                              const struct fb_fillrect *rect)
{
        struct hvfb_par *par = p->par;

        cfb_fillrect(p, rect);
        if (par->synchronous_fb)
                synthvid_update(p, 0, 0, INT_MAX, INT_MAX);
        else
                hvfb_ondemand_refresh_throttle(par, rect->dx, rect->dy,
                                               rect->width, rect->height);
}

static void hvfb_cfb_copyarea(struct fb_info *p,
                              const struct fb_copyarea *area)
{
        struct hvfb_par *par = p->par;

        cfb_copyarea(p, area);
        if (par->synchronous_fb)
                synthvid_update(p, 0, 0, INT_MAX, INT_MAX);
        else
                hvfb_ondemand_refresh_throttle(par, area->dx, area->dy,
                                               area->width, area->height);
}

static void hvfb_cfb_imageblit(struct fb_info *p,
                               const struct fb_image *image)
{
        struct hvfb_par *par = p->par;

        cfb_imageblit(p, image);
        if (par->synchronous_fb)
                synthvid_update(p, 0, 0, INT_MAX, INT_MAX);
        else
                hvfb_ondemand_refresh_throttle(par, image->dx, image->dy,
                                               image->width, image->height);
}

static const struct fb_ops hvfb_ops = {
        .owner = THIS_MODULE,
        .fb_check_var = hvfb_check_var,
        .fb_set_par = hvfb_set_par,
        .fb_setcolreg = hvfb_setcolreg,
        .fb_fillrect = hvfb_cfb_fillrect,
        .fb_copyarea = hvfb_cfb_copyarea,
        .fb_imageblit = hvfb_cfb_imageblit,
        .fb_blank = hvfb_blank,
};


/* Get options from kernel paramenter "video=" */
static void hvfb_get_option(struct fb_info *info)
{
        struct hvfb_par *par = info->par;
        char *opt = NULL, *p;
        uint x = 0, y = 0;

        if (fb_get_options(KBUILD_MODNAME, &opt) || !opt || !*opt)
                return;

        p = strsep(&opt, "x");
        if (!*p || kstrtouint(p, 0, &x) ||
            !opt || !*opt || kstrtouint(opt, 0, &y)) {
                pr_err("Screen option is invalid: skipped\n");
                return;
        }

        if (x < HVFB_WIDTH_MIN || y < HVFB_HEIGHT_MIN ||
            (synthvid_ver_ge(par->synthvid_version, SYNTHVID_VERSION_WIN10) &&
            (x > screen_width_max || y > screen_height_max)) ||
            (par->synthvid_version == SYNTHVID_VERSION_WIN8 &&
             x * y * screen_depth / 8 > SYNTHVID_FB_SIZE_WIN8) ||
            (par->synthvid_version == SYNTHVID_VERSION_WIN7 &&
             (x > SYNTHVID_WIDTH_MAX_WIN7 || y > SYNTHVID_HEIGHT_MAX_WIN7))) {
                pr_err("Screen resolution option is out of range: skipped\n");
                return;
        }

        screen_width = x;
        screen_height = y;
        return;
}

/*
 * Allocate enough contiguous physical memory.
 * Return physical address if succeeded or -1 if failed.
 */
static phys_addr_t hvfb_get_phymem(struct hv_device *hdev,
                                   unsigned int request_size)
{
        struct page *page = NULL;
        dma_addr_t dma_handle;
        void *vmem;
        phys_addr_t paddr = 0;
        unsigned int order = get_order(request_size);

        if (request_size == 0)
                return -1;

        if (order < MAX_ORDER) {
                /* Call alloc_pages if the size is less than 2^MAX_ORDER */
                page = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
                if (!page)
                        return -1;

                paddr = (page_to_pfn(page) << PAGE_SHIFT);
        } else {
                /* Allocate from CMA */
                hdev->device.coherent_dma_mask = DMA_BIT_MASK(64);

                vmem = dma_alloc_coherent(&hdev->device,
                                          round_up(request_size, PAGE_SIZE),
                                          &dma_handle,
                                          GFP_KERNEL | __GFP_NOWARN);

                if (!vmem)
                        return -1;

                paddr = virt_to_phys(vmem);
        }

        return paddr;
}

/* Release contiguous physical memory */
static void hvfb_release_phymem(struct hv_device *hdev,
                                phys_addr_t paddr, unsigned int size)
{

        unsigned int order = get_order(size);

        if (order < MAX_ORDER)
                __free_pages(pfn_to_page(paddr >> PAGE_SHIFT), order);
        else
                dma_free_coherent(&hdev->device,
                                  round_up(size, PAGE_SIZE),
                                  phys_to_virt(paddr),
                                  paddr);
}


/* Get framebuffer memory from Hyper-V video pci space */
static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
{
        struct hvfb_par *par = info->par;
        struct pci_dev *pdev  = NULL;
        void __iomem *fb_virt;
        int gen2vm = efi_enabled(EFI_BOOT);
        resource_size_t pot_start, pot_end;
        phys_addr_t paddr;
        int ret;

        info->apertures = alloc_apertures(1);
        if (!info->apertures)
                return -ENOMEM;

        if (!gen2vm) {
                pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,
                        PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
                if (!pdev) {
                        pr_err("Unable to find PCI Hyper-V video\n");
                        kfree(info->apertures);
                        return -ENODEV;
                }

                info->apertures->ranges[0].base = pci_resource_start(pdev, 0);
                info->apertures->ranges[0].size = pci_resource_len(pdev, 0);

                /*
                 * For Gen 1 VM, we can directly use the contiguous memory
                 * from VM. If we succeed, deferred IO happens directly
                 * on this allocated framebuffer memory, avoiding extra
                 * memory copy.
                 */
                paddr = hvfb_get_phymem(hdev, screen_fb_size);
                if (paddr != (phys_addr_t) -1) {
                        par->mmio_pp = paddr;
                        par->mmio_vp = par->dio_vp = __va(paddr);

                        info->fix.smem_start = paddr;
                        info->fix.smem_len = screen_fb_size;
                        info->screen_base = par->mmio_vp;
                        info->screen_size = screen_fb_size;

                        par->need_docopy = false;
                        goto getmem_done;
                }
                pr_info("Unable to allocate enough contiguous physical memory on Gen 1 VM. Using MMIO instead.\n");
        } else {
                info->apertures->ranges[0].base = screen_info.lfb_base;
                info->apertures->ranges[0].size = screen_info.lfb_size;
        }

        /*
         * Cannot use the contiguous physical memory.
         * Allocate mmio space for framebuffer.
         */
        dio_fb_size =
                screen_width * screen_height * screen_depth / 8;

        if (gen2vm) {
                pot_start = 0;
                pot_end = -1;
        } else {
                if (!(pci_resource_flags(pdev, 0) & IORESOURCE_MEM) ||
                    pci_resource_len(pdev, 0) < screen_fb_size) {
                        pr_err("Resource not available or (0x%lx < 0x%lx)\n",
                               (unsigned long) pci_resource_len(pdev, 0),
                               (unsigned long) screen_fb_size);
                        goto err1;
                }

                pot_end = pci_resource_end(pdev, 0);
                pot_start = pot_end - screen_fb_size + 1;
        }

        ret = vmbus_allocate_mmio(&par->mem, hdev, pot_start, pot_end,
                                  screen_fb_size, 0x100000, true);
        if (ret != 0) {
                pr_err("Unable to allocate framebuffer memory\n");
                goto err1;
        }

        fb_virt = ioremap(par->mem->start, screen_fb_size);
        if (!fb_virt)
                goto err2;

        /* Allocate memory for deferred IO */
        par->dio_vp = vzalloc(round_up(dio_fb_size, PAGE_SIZE));
        if (par->dio_vp == NULL)
                goto err3;

        /* Physical address of FB device */
        par->mmio_pp = par->mem->start;
        /* Virtual address of FB device */
        par->mmio_vp = (unsigned char *) fb_virt;

        info->fix.smem_start = par->mem->start;
        info->fix.smem_len = dio_fb_size;
        info->screen_base = par->dio_vp;
        info->screen_size = dio_fb_size;

getmem_done:
        remove_conflicting_framebuffers(info->apertures,
                                        KBUILD_MODNAME, false);
        if (!gen2vm)
                pci_dev_put(pdev);
        kfree(info->apertures);

        return 0;

err3:
        iounmap(fb_virt);
err2:
        vmbus_free_mmio(par->mem->start, screen_fb_size);
        par->mem = NULL;
err1:
        if (!gen2vm)
                pci_dev_put(pdev);
        kfree(info->apertures);

        return -ENOMEM;
}

/* Release the framebuffer */
static void hvfb_putmem(struct hv_device *hdev, struct fb_info *info)
{
        struct hvfb_par *par = info->par;

        if (par->need_docopy) {
                vfree(par->dio_vp);
                iounmap(info->screen_base);
                vmbus_free_mmio(par->mem->start, screen_fb_size);
        } else {
                hvfb_release_phymem(hdev, info->fix.smem_start,
                                    screen_fb_size);
        }

        par->mem = NULL;
}


static int hvfb_probe(struct hv_device *hdev,
                      const struct hv_vmbus_device_id *dev_id)
{
        struct fb_info *info;
        struct hvfb_par *par;
        int ret;

        info = framebuffer_alloc(sizeof(struct hvfb_par), &hdev->device);
        if (!info)
                return -ENOMEM;

        par = info->par;
        par->info = info;
        par->fb_ready = false;
        par->need_docopy = true;
        init_completion(&par->wait);
        INIT_DELAYED_WORK(&par->dwork, hvfb_update_work);

        par->delayed_refresh = false;
        spin_lock_init(&par->delayed_refresh_lock);
        par->x1 = par->y1 = INT_MAX;
        par->x2 = par->y2 = 0;

        /* Connect to VSP */
        hv_set_drvdata(hdev, info);
        ret = synthvid_connect_vsp(hdev);
        if (ret) {
                pr_err("Unable to connect to VSP\n");
                goto error1;
        }

        hvfb_get_option(info);
        pr_info("Screen resolution: %dx%d, Color depth: %d\n",
                screen_width, screen_height, screen_depth);

        ret = hvfb_getmem(hdev, info);
        if (ret) {
                pr_err("No memory for framebuffer\n");
                goto error2;
        }

        /* Set up fb_info */
        info->flags = FBINFO_DEFAULT;

        info->var.xres_virtual = info->var.xres = screen_width;
        info->var.yres_virtual = info->var.yres = screen_height;
        info->var.bits_per_pixel = screen_depth;

        if (info->var.bits_per_pixel == 16) {
                info->var.red = (struct fb_bitfield){11, 5, 0};
                info->var.green = (struct fb_bitfield){5, 6, 0};
                info->var.blue = (struct fb_bitfield){0, 5, 0};
                info->var.transp = (struct fb_bitfield){0, 0, 0};
        } else {
                info->var.red = (struct fb_bitfield){16, 8, 0};
                info->var.green = (struct fb_bitfield){8, 8, 0};
                info->var.blue = (struct fb_bitfield){0, 8, 0};
                info->var.transp = (struct fb_bitfield){24, 8, 0};
        }

        info->var.activate = FB_ACTIVATE_NOW;
        info->var.height = -1;
        info->var.width = -1;
        info->var.vmode = FB_VMODE_NONINTERLACED;

        strcpy(info->fix.id, KBUILD_MODNAME);
        info->fix.type = FB_TYPE_PACKED_PIXELS;
        info->fix.visual = FB_VISUAL_TRUECOLOR;
        info->fix.line_length = screen_width * screen_depth / 8;
        info->fix.accel = FB_ACCEL_NONE;

        info->fbops = &hvfb_ops;
        info->pseudo_palette = par->pseudo_palette;

        /* Initialize deferred IO */
        info->fbdefio = &synthvid_defio;
        fb_deferred_io_init(info);

        /* Send config to host */
        ret = synthvid_send_config(hdev);
        if (ret)
                goto error;

        ret = register_framebuffer(info);
        if (ret) {
                pr_err("Unable to register framebuffer\n");
                goto error;
        }

        par->fb_ready = true;

        par->synchronous_fb = false;
        par->hvfb_panic_nb.notifier_call = hvfb_on_panic;
        atomic_notifier_chain_register(&panic_notifier_list,
                                       &par->hvfb_panic_nb);

        return 0;

error:
        fb_deferred_io_cleanup(info);
        hvfb_putmem(hdev, info);
error2:
        vmbus_close(hdev->channel);
error1:
        cancel_delayed_work_sync(&par->dwork);
        hv_set_drvdata(hdev, NULL);
        framebuffer_release(info);
        return ret;
}


static int hvfb_remove(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;

        atomic_notifier_chain_unregister(&panic_notifier_list,
                                         &par->hvfb_panic_nb);

        par->update = false;
        par->fb_ready = false;

        fb_deferred_io_cleanup(info);

        unregister_framebuffer(info);
        cancel_delayed_work_sync(&par->dwork);

        vmbus_close(hdev->channel);
        hv_set_drvdata(hdev, NULL);

        hvfb_putmem(hdev, info);
        framebuffer_release(info);

        return 0;
}

static int hvfb_suspend(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;

        console_lock();

        /* 1 means do suspend */
        fb_set_suspend(info, 1);

        cancel_delayed_work_sync(&par->dwork);
        cancel_delayed_work_sync(&info->deferred_work);

        par->update_saved = par->update;
        par->update = false;
        par->fb_ready = false;

        vmbus_close(hdev->channel);

        console_unlock();

        return 0;
}

static int hvfb_resume(struct hv_device *hdev)
{
        struct fb_info *info = hv_get_drvdata(hdev);
        struct hvfb_par *par = info->par;
        int ret;

        console_lock();

        ret = synthvid_connect_vsp(hdev);
        if (ret != 0)
                goto out;

        ret = synthvid_send_config(hdev);
        if (ret != 0) {
                vmbus_close(hdev->channel);
                goto out;
        }

        par->fb_ready = true;
        par->update = par->update_saved;

        schedule_delayed_work(&info->deferred_work, info->fbdefio->delay);
        schedule_delayed_work(&par->dwork, HVFB_UPDATE_DELAY);

        /* 0 means do resume */
        fb_set_suspend(info, 0);

out:
        console_unlock();

        return ret;
}


static const struct pci_device_id pci_stub_id_table[] = {
        {
                .vendor      = PCI_VENDOR_ID_MICROSOFT,
                .device      = PCI_DEVICE_ID_HYPERV_VIDEO,
        },
        { /* end of list */ }
};

static const struct hv_vmbus_device_id id_table[] = {
        /* Synthetic Video Device GUID */
        {HV_SYNTHVID_GUID},
        {}
};

MODULE_DEVICE_TABLE(pci, pci_stub_id_table);
MODULE_DEVICE_TABLE(vmbus, id_table);

static struct hv_driver hvfb_drv = {
        .name = KBUILD_MODNAME,
        .id_table = id_table,
        .probe = hvfb_probe,
        .remove = hvfb_remove,
        .suspend = hvfb_suspend,
        .resume = hvfb_resume,
        .driver = {
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};

static int hvfb_pci_stub_probe(struct pci_dev *pdev,
                               const struct pci_device_id *ent)
{
        return 0;
}

static void hvfb_pci_stub_remove(struct pci_dev *pdev)
{
}

static struct pci_driver hvfb_pci_stub_driver = {
        .name =         KBUILD_MODNAME,
        .id_table =     pci_stub_id_table,
        .probe =        hvfb_pci_stub_probe,
        .remove =       hvfb_pci_stub_remove,
        .driver = {
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        }
};

static int __init hvfb_drv_init(void)
{
        int ret;

        ret = vmbus_driver_register(&hvfb_drv);
        if (ret != 0)
                return ret;

        ret = pci_register_driver(&hvfb_pci_stub_driver);
        if (ret != 0) {
                vmbus_driver_unregister(&hvfb_drv);
                return ret;
        }

        return 0;
}

static void __exit hvfb_drv_exit(void)
{
        pci_unregister_driver(&hvfb_pci_stub_driver);
        vmbus_driver_unregister(&hvfb_drv);
}

module_init(hvfb_drv_init);
module_exit(hvfb_drv_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Microsoft Hyper-V Synthetic Video Frame Buffer Driver");