/*
 * OpenCores VGA/LCD 2.0 core frame buffer driver
 *
 * Copyright (C) 2013 Stefan Kristiansson, stefan.kristiansson@saunalahti.fi
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */

#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/errno.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/string.h>
#include <linux/slab.h>

/* OCFB register defines */
#define OCFB_CTRL       0x000
#define OCFB_STAT       0x004
#define OCFB_HTIM       0x008
#define OCFB_VTIM       0x00c
#define OCFB_HVLEN      0x010
#define OCFB_VBARA      0x014
#define OCFB_PALETTE    0x800

#define OCFB_CTRL_VEN   0x00000001 /* Video Enable */
#define OCFB_CTRL_HIE   0x00000002 /* HSync Interrupt Enable */
#define OCFB_CTRL_PC    0x00000800 /* 8-bit Pseudo Color Enable*/
#define OCFB_CTRL_CD8   0x00000000 /* Color Depth 8 */
#define OCFB_CTRL_CD16  0x00000200 /* Color Depth 16 */
#define OCFB_CTRL_CD24  0x00000400 /* Color Depth 24 */
#define OCFB_CTRL_CD32  0x00000600 /* Color Depth 32 */
#define OCFB_CTRL_VBL1  0x00000000 /* Burst Length 1 */
#define OCFB_CTRL_VBL2  0x00000080 /* Burst Length 2 */
#define OCFB_CTRL_VBL4  0x00000100 /* Burst Length 4 */
#define OCFB_CTRL_VBL8  0x00000180 /* Burst Length 8 */

#define PALETTE_SIZE    256

#define OCFB_NAME       "OC VGA/LCD"

static char *mode_option;

static const struct fb_videomode default_mode = {
        /* 640x480 @ 60 Hz, 31.5 kHz hsync */
        NULL, 60, 640, 480, 39721, 40, 24, 32, 11, 96, 2,
        0, FB_VMODE_NONINTERLACED
};

struct ocfb_dev {
        struct fb_info info;
        void __iomem *regs;
        /* flag indicating whether the regs are little endian accessed */
        int little_endian;
        /* Physical and virtual addresses of framebuffer */
        dma_addr_t fb_phys;
        void __iomem *fb_virt;
        u32 pseudo_palette[PALETTE_SIZE];
};

#ifndef MODULE
static int __init ocfb_setup(char *options)
{
        char *curr_opt;

        if (!options || !*options)
                return 0;

        while ((curr_opt = strsep(&options, ",")) != NULL) {
                if (!*curr_opt)
                        continue;
                mode_option = curr_opt;
        }

        return 0;
}
#endif

static inline u32 ocfb_readreg(struct ocfb_dev *fbdev, loff_t offset)
{
        if (fbdev->little_endian)
                return ioread32(fbdev->regs + offset);
        else
                return ioread32be(fbdev->regs + offset);
}

static void ocfb_writereg(struct ocfb_dev *fbdev, loff_t offset, u32 data)
{
        if (fbdev->little_endian)
                iowrite32(data, fbdev->regs + offset);
        else
                iowrite32be(data, fbdev->regs + offset);
}

static int ocfb_setupfb(struct ocfb_dev *fbdev)
{
        unsigned long bpp_config;
        struct fb_var_screeninfo *var = &fbdev->info.var;
        struct device *dev = fbdev->info.device;
        u32 hlen;
        u32 vlen;

        /* Disable display */
        ocfb_writereg(fbdev, OCFB_CTRL, 0);

        /* Register framebuffer address */
        fbdev->little_endian = 0;
        ocfb_writereg(fbdev, OCFB_VBARA, fbdev->fb_phys);

        /* Detect endianess */
        if (ocfb_readreg(fbdev, OCFB_VBARA) != fbdev->fb_phys) {
                fbdev->little_endian = 1;
                ocfb_writereg(fbdev, OCFB_VBARA, fbdev->fb_phys);
        }

        /* Horizontal timings */
        ocfb_writereg(fbdev, OCFB_HTIM, (var->hsync_len - 1) << 24 |
                      (var->left_margin - 1) << 16 | (var->xres - 1));

        /* Vertical timings */
        ocfb_writereg(fbdev, OCFB_VTIM, (var->vsync_len - 1) << 24 |
                      (var->upper_margin - 1) << 16 | (var->yres - 1));

        /* Total length of frame */
        hlen = var->left_margin + var->right_margin + var->hsync_len +
                var->xres;

        vlen = var->upper_margin + var->lower_margin + var->vsync_len +
                var->yres;

        ocfb_writereg(fbdev, OCFB_HVLEN, (hlen - 1) << 16 | (vlen - 1));

        bpp_config = OCFB_CTRL_CD8;
        switch (var->bits_per_pixel) {
        case 8:
                if (!var->grayscale)
                        bpp_config |= OCFB_CTRL_PC;  /* enable palette */
                break;

        case 16:
                bpp_config |= OCFB_CTRL_CD16;
                break;

        case 24:
                bpp_config |= OCFB_CTRL_CD24;
                break;

        case 32:
                bpp_config |= OCFB_CTRL_CD32;
                break;

        default:
                dev_err(dev, "no bpp specified\n");
                break;
        }

        /* maximum (8) VBL (video memory burst length) */
        bpp_config |= OCFB_CTRL_VBL8;

        /* Enable output */
        ocfb_writereg(fbdev, OCFB_CTRL, (OCFB_CTRL_VEN | bpp_config));

        return 0;
}

static int ocfb_setcolreg(unsigned regno, unsigned red, unsigned green,
                          unsigned blue, unsigned transp,
                          struct fb_info *info)
{
        struct ocfb_dev *fbdev = (struct ocfb_dev *)info->par;
        u32 color;

        if (regno >= info->cmap.len) {
                dev_err(info->device, "regno >= cmap.len\n");
                return 1;
        }

        if (info->var.grayscale) {
                /* grayscale = 0.30*R + 0.59*G + 0.11*B */
                red = green = blue = (red * 77 + green * 151 + blue * 28) >> 8;
        }

        red >>= (16 - info->var.red.length);
        green >>= (16 - info->var.green.length);
        blue >>= (16 - info->var.blue.length);
        transp >>= (16 - info->var.transp.length);

        if (info->var.bits_per_pixel == 8 && !info->var.grayscale) {
                regno <<= 2;
                color = (red << 16) | (green << 8) | blue;
                ocfb_writereg(fbdev, OCFB_PALETTE + regno, color);
        } else {
                ((u32 *)(info->pseudo_palette))[regno] =
                        (red << info->var.red.offset) |
                        (green << info->var.green.offset) |
                        (blue << info->var.blue.offset) |
                        (transp << info->var.transp.offset);
        }

        return 0;
}

static int ocfb_init_fix(struct ocfb_dev *fbdev)
{
        struct fb_var_screeninfo *var = &fbdev->info.var;
        struct fb_fix_screeninfo *fix = &fbdev->info.fix;

        strcpy(fix->id, OCFB_NAME);

        fix->line_length = var->xres * var->bits_per_pixel/8;
        fix->smem_len = fix->line_length * var->yres;
        fix->type = FB_TYPE_PACKED_PIXELS;

        if (var->bits_per_pixel == 8 && !var->grayscale)
                fix->visual = FB_VISUAL_PSEUDOCOLOR;
        else
                fix->visual = FB_VISUAL_TRUECOLOR;

        return 0;
}

static int ocfb_init_var(struct ocfb_dev *fbdev)
{
        struct fb_var_screeninfo *var = &fbdev->info.var;

        var->accel_flags = FB_ACCEL_NONE;
        var->activate = FB_ACTIVATE_NOW;
        var->xres_virtual = var->xres;
        var->yres_virtual = var->yres;

        switch (var->bits_per_pixel) {
        case 8:
                var->transp.offset = 0;
                var->transp.length = 0;
                var->red.offset = 0;
                var->red.length = 8;
                var->green.offset = 0;
                var->green.length = 8;
                var->blue.offset = 0;
                var->blue.length = 8;
                break;

        case 16:
                var->transp.offset = 0;
                var->transp.length = 0;
                var->red.offset = 11;
                var->red.length = 5;
                var->green.offset = 5;
                var->green.length = 6;
                var->blue.offset = 0;
                var->blue.length  = 5;
                break;

        case 24:
                var->transp.offset = 0;
                var->transp.length = 0;
                var->red.offset = 16;
                var->red.length = 8;
                var->green.offset = 8;
                var->green.length = 8;
                var->blue.offset = 0;
                var->blue.length = 8;
                break;

        case 32:
                var->transp.offset = 24;
                var->transp.length = 8;
                var->red.offset = 16;
                var->red.length = 8;
                var->green.offset = 8;
                var->green.length = 8;
                var->blue.offset = 0;
                var->blue.length = 8;
                break;
        }

        return 0;
}

static const struct fb_ops ocfb_ops = {
        .owner          = THIS_MODULE,
        FB_DEFAULT_IOMEM_OPS,
        .fb_setcolreg   = ocfb_setcolreg,
};

static int ocfb_probe(struct platform_device *pdev)
{
        int ret = 0;
        struct ocfb_dev *fbdev;
        int fbsize;

        fbdev = devm_kzalloc(&pdev->dev, sizeof(*fbdev), GFP_KERNEL);
        if (!fbdev)
                return -ENOMEM;

        platform_set_drvdata(pdev, fbdev);

        fbdev->info.fbops = &ocfb_ops;
        fbdev->info.device = &pdev->dev;
        fbdev->info.par = fbdev;

        /* Video mode setup */
        if (!fb_find_mode(&fbdev->info.var, &fbdev->info, mode_option,
                          NULL, 0, &default_mode, 16)) {
                dev_err(&pdev->dev, "No valid video modes found\n");
                return -EINVAL;
        }
        ocfb_init_var(fbdev);
        ocfb_init_fix(fbdev);

        fbdev->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(fbdev->regs))
                return PTR_ERR(fbdev->regs);

        /* Allocate framebuffer memory */
        fbsize = fbdev->info.fix.smem_len;
        fbdev->fb_virt = dma_alloc_coherent(&pdev->dev, PAGE_ALIGN(fbsize),
                                            &fbdev->fb_phys, GFP_KERNEL);
        if (!fbdev->fb_virt) {
                dev_err(&pdev->dev,
                        "Frame buffer memory allocation failed\n");
                return -ENOMEM;
        }
        fbdev->info.fix.smem_start = fbdev->fb_phys;
        fbdev->info.screen_base = fbdev->fb_virt;
        fbdev->info.pseudo_palette = fbdev->pseudo_palette;

        /* Clear framebuffer */
        memset_io(fbdev->fb_virt, 0, fbsize);

        /* Setup and enable the framebuffer */
        ocfb_setupfb(fbdev);

        if (fbdev->little_endian)
                fbdev->info.flags |= FBINFO_FOREIGN_ENDIAN;

        /* Allocate color map */
        ret = fb_alloc_cmap(&fbdev->info.cmap, PALETTE_SIZE, 0);
        if (ret) {
                dev_err(&pdev->dev, "Color map allocation failed\n");
                goto err_dma_free;
        }

        /* Register framebuffer */
        ret = register_framebuffer(&fbdev->info);
        if (ret) {
                dev_err(&pdev->dev, "Framebuffer registration failed\n");
                goto err_dealloc_cmap;
        }

        return 0;

err_dealloc_cmap:
        fb_dealloc_cmap(&fbdev->info.cmap);

err_dma_free:
        dma_free_coherent(&pdev->dev, PAGE_ALIGN(fbsize), fbdev->fb_virt,
                          fbdev->fb_phys);

        return ret;
}

static void ocfb_remove(struct platform_device *pdev)
{
        struct ocfb_dev *fbdev = platform_get_drvdata(pdev);

        unregister_framebuffer(&fbdev->info);
        fb_dealloc_cmap(&fbdev->info.cmap);
        dma_free_coherent(&pdev->dev, PAGE_ALIGN(fbdev->info.fix.smem_len),
                          fbdev->fb_virt, fbdev->fb_phys);

        /* Disable display */
        ocfb_writereg(fbdev, OCFB_CTRL, 0);

        platform_set_drvdata(pdev, NULL);
}

static const struct of_device_id ocfb_match[] = {
        { .compatible = "opencores,ocfb", },
        {},
};
MODULE_DEVICE_TABLE(of, ocfb_match);

static struct platform_driver ocfb_driver = {
        .probe  = ocfb_probe,
        .remove = ocfb_remove,
        .driver = {
                .name = "ocfb_fb",
                .of_match_table = ocfb_match,
        }
};

/*
 * Init and exit routines
 */
static int __init ocfb_init(void)
{
#ifndef MODULE
        char *option = NULL;

        if (fb_get_options("ocfb", &option))
                return -ENODEV;
        ocfb_setup(option);
#endif
        return platform_driver_register(&ocfb_driver);
}

static void __exit ocfb_exit(void)
{
        platform_driver_unregister(&ocfb_driver);
}

module_init(ocfb_init);
module_exit(ocfb_exit);

MODULE_AUTHOR("Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>");
MODULE_DESCRIPTION("OpenCores VGA/LCD 2.0 frame buffer driver");
MODULE_LICENSE("GPL v2");
module_param(mode_option, charp, 0);
MODULE_PARM_DESC(mode_option, "Video mode ('<xres>x<yres>[-<bpp>][@refresh]')");