/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2016 Noralf Trønnes
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/io.h>

#include <drm/drm_format_helper.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_rect.h>

static unsigned int clip_offset(struct drm_rect *clip,
                                unsigned int pitch, unsigned int cpp)
{
        return clip->y1 * pitch + clip->x1 * cpp;
}

/**
 * drm_fb_memcpy - Copy clip buffer
 * @dst: Destination buffer
 * @vaddr: Source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 *
 * This function does not apply clipping on dst, i.e. the destination
 * is a small buffer containing the clip rect only.
 */
void drm_fb_memcpy(void *dst, void *vaddr, struct drm_framebuffer *fb,
                   struct drm_rect *clip)
{
        unsigned int cpp = fb->format->cpp[0];
        size_t len = (clip->x2 - clip->x1) * cpp;
        unsigned int y, lines = clip->y2 - clip->y1;

        vaddr += clip_offset(clip, fb->pitches[0], cpp);
        for (y = 0; y < lines; y++) {
                memcpy(dst, vaddr, len);
                vaddr += fb->pitches[0];
                dst += len;
        }
}
EXPORT_SYMBOL(drm_fb_memcpy);

/**
 * drm_fb_memcpy_dstclip - Copy clip buffer
 * @dst: Destination buffer (iomem)
 * @vaddr: Source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 *
 * This function applies clipping on dst, i.e. the destination is a
 * full (iomem) framebuffer but only the clip rect content is copied over.
 */
void drm_fb_memcpy_dstclip(void __iomem *dst, void *vaddr,
                           struct drm_framebuffer *fb,
                           struct drm_rect *clip)
{
        unsigned int cpp = fb->format->cpp[0];
        unsigned int offset = clip_offset(clip, fb->pitches[0], cpp);
        size_t len = (clip->x2 - clip->x1) * cpp;
        unsigned int y, lines = clip->y2 - clip->y1;

        vaddr += offset;
        dst += offset;
        for (y = 0; y < lines; y++) {
                memcpy_toio(dst, vaddr, len);
                vaddr += fb->pitches[0];
                dst += fb->pitches[0];
        }
}
EXPORT_SYMBOL(drm_fb_memcpy_dstclip);

/**
 * drm_fb_swab16 - Swap bytes into clip buffer
 * @dst: RGB565 destination buffer
 * @vaddr: RGB565 source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 */
void drm_fb_swab16(u16 *dst, void *vaddr, struct drm_framebuffer *fb,
                   struct drm_rect *clip)
{
        size_t len = (clip->x2 - clip->x1) * sizeof(u16);
        unsigned int x, y;
        u16 *src, *buf;

        /*
         * The cma memory is write-combined so reads are uncached.
         * Speed up by fetching one line at a time.
         */
        buf = kmalloc(len, GFP_KERNEL);
        if (!buf)
                return;

        for (y = clip->y1; y < clip->y2; y++) {
                src = vaddr + (y * fb->pitches[0]);
                src += clip->x1;
                memcpy(buf, src, len);
                src = buf;
                for (x = clip->x1; x < clip->x2; x++)
                        *dst++ = swab16(*src++);
        }

        kfree(buf);
}
EXPORT_SYMBOL(drm_fb_swab16);

static void drm_fb_xrgb8888_to_rgb565_line(u16 *dbuf, u32 *sbuf,
                                           unsigned int pixels,
                                           bool swab)
{
        unsigned int x;
        u16 val16;

        for (x = 0; x < pixels; x++) {
                val16 = ((sbuf[x] & 0x00F80000) >> 8) |
                        ((sbuf[x] & 0x0000FC00) >> 5) |
                        ((sbuf[x] & 0x000000F8) >> 3);
                if (swab)
                        dbuf[x] = swab16(val16);
                else
                        dbuf[x] = val16;
        }
}

/**
 * drm_fb_xrgb8888_to_rgb565 - Convert XRGB8888 to RGB565 clip buffer
 * @dst: RGB565 destination buffer
 * @vaddr: XRGB8888 source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 * @swab: Swap bytes
 *
 * Drivers can use this function for RGB565 devices that don't natively
 * support XRGB8888.
 *
 * This function does not apply clipping on dst, i.e. the destination
 * is a small buffer containing the clip rect only.
 */
void drm_fb_xrgb8888_to_rgb565(void *dst, void *vaddr,
                               struct drm_framebuffer *fb,
                               struct drm_rect *clip, bool swab)
{
        size_t linepixels = clip->x2 - clip->x1;
        size_t src_len = linepixels * sizeof(u32);
        size_t dst_len = linepixels * sizeof(u16);
        unsigned y, lines = clip->y2 - clip->y1;
        void *sbuf;

        /*
         * The cma memory is write-combined so reads are uncached.
         * Speed up by fetching one line at a time.
         */
        sbuf = kmalloc(src_len, GFP_KERNEL);
        if (!sbuf)
                return;

        vaddr += clip_offset(clip, fb->pitches[0], sizeof(u32));
        for (y = 0; y < lines; y++) {
                memcpy(sbuf, vaddr, src_len);
                drm_fb_xrgb8888_to_rgb565_line(dst, sbuf, linepixels, swab);
                vaddr += fb->pitches[0];
                dst += dst_len;
        }

        kfree(sbuf);
}
EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565);

/**
 * drm_fb_xrgb8888_to_rgb565_dstclip - Convert XRGB8888 to RGB565 clip buffer
 * @dst: RGB565 destination buffer (iomem)
 * @dst_pitch: destination buffer pitch
 * @vaddr: XRGB8888 source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 * @swab: Swap bytes
 *
 * Drivers can use this function for RGB565 devices that don't natively
 * support XRGB8888.
 *
 * This function applies clipping on dst, i.e. the destination is a
 * full (iomem) framebuffer but only the clip rect content is copied over.
 */
void drm_fb_xrgb8888_to_rgb565_dstclip(void __iomem *dst, unsigned int dst_pitch,
                                       void *vaddr, struct drm_framebuffer *fb,
                                       struct drm_rect *clip, bool swab)
{
        size_t linepixels = clip->x2 - clip->x1;
        size_t dst_len = linepixels * sizeof(u16);
        unsigned y, lines = clip->y2 - clip->y1;
        void *dbuf;

        dbuf = kmalloc(dst_len, GFP_KERNEL);
        if (!dbuf)
                return;

        vaddr += clip_offset(clip, fb->pitches[0], sizeof(u32));
        dst += clip_offset(clip, dst_pitch, sizeof(u16));
        for (y = 0; y < lines; y++) {
                drm_fb_xrgb8888_to_rgb565_line(dbuf, vaddr, linepixels, swab);
                memcpy_toio(dst, dbuf, dst_len);
                vaddr += fb->pitches[0];
                dst += dst_len;
        }

        kfree(dbuf);
}
EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565_dstclip);

static void drm_fb_xrgb8888_to_rgb888_line(u8 *dbuf, u32 *sbuf,
                                           unsigned int pixels)
{
        unsigned int x;

        for (x = 0; x < pixels; x++) {
                *dbuf++ = (sbuf[x] & 0x000000FF) >>  0;
                *dbuf++ = (sbuf[x] & 0x0000FF00) >>  8;
                *dbuf++ = (sbuf[x] & 0x00FF0000) >> 16;
        }
}

/**
 * drm_fb_xrgb8888_to_rgb888_dstclip - Convert XRGB8888 to RGB888 clip buffer
 * @dst: RGB565 destination buffer (iomem)
 * @dst_pitch: destination buffer pitch
 * @vaddr: XRGB8888 source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 *
 * Drivers can use this function for RGB888 devices that don't natively
 * support XRGB8888.
 *
 * This function applies clipping on dst, i.e. the destination is a
 * full (iomem) framebuffer but only the clip rect content is copied over.
 */
void drm_fb_xrgb8888_to_rgb888_dstclip(void __iomem *dst, unsigned int dst_pitch,
                                       void *vaddr, struct drm_framebuffer *fb,
                                       struct drm_rect *clip)
{
        size_t linepixels = clip->x2 - clip->x1;
        size_t dst_len = linepixels * 3;
        unsigned y, lines = clip->y2 - clip->y1;
        void *dbuf;

        dbuf = kmalloc(dst_len, GFP_KERNEL);
        if (!dbuf)
                return;

        vaddr += clip_offset(clip, fb->pitches[0], sizeof(u32));
        dst += clip_offset(clip, dst_pitch, sizeof(u16));
        for (y = 0; y < lines; y++) {
                drm_fb_xrgb8888_to_rgb888_line(dbuf, vaddr, linepixels);
                memcpy_toio(dst, dbuf, dst_len);
                vaddr += fb->pitches[0];
                dst += dst_len;
        }

        kfree(dbuf);
}
EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888_dstclip);

/**
 * drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
 * @dst: 8-bit grayscale destination buffer
 * @vaddr: XRGB8888 source buffer
 * @fb: DRM framebuffer
 * @clip: Clip rectangle area to copy
 *
 * Drm doesn't have native monochrome or grayscale support.
 * Such drivers can announce the commonly supported XR24 format to userspace
 * and use this function to convert to the native format.
 *
 * Monochrome drivers will use the most significant bit,
 * where 1 means foreground color and 0 background color.
 *
 * ITU BT.601 is used for the RGB -> luma (brightness) conversion.
 */
void drm_fb_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
                               struct drm_rect *clip)
{
        unsigned int len = (clip->x2 - clip->x1) * sizeof(u32);
        unsigned int x, y;
        void *buf;
        u32 *src;

        if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
                return;
        /*
         * The cma memory is write-combined so reads are uncached.
         * Speed up by fetching one line at a time.
         */
        buf = kmalloc(len, GFP_KERNEL);
        if (!buf)
                return;

        for (y = clip->y1; y < clip->y2; y++) {
                src = vaddr + (y * fb->pitches[0]);
                src += clip->x1;
                memcpy(buf, src, len);
                src = buf;
                for (x = clip->x1; x < clip->x2; x++) {
                        u8 r = (*src & 0x00ff0000) >> 16;
                        u8 g = (*src & 0x0000ff00) >> 8;
                        u8 b =  *src & 0x000000ff;

                        /* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
                        *dst++ = (3 * r + 6 * g + b) / 10;
                        src++;
                }
        }

        kfree(buf);
}
EXPORT_SYMBOL(drm_fb_xrgb8888_to_gray8);