// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat
 *
 * based in parts on udlfb.c:
 * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
 * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
 * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>

 */

#include <linux/dma-buf.h>

#include <drm/drm_atomic_helper.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drm_damage_helper.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_vblank.h>

#include "udl_drv.h"

#define UDL_COLOR_DEPTH_16BPP   0

/*
 * All DisplayLink bulk operations start with 0xAF, followed by specific code
 * All operations are written to buffers which then later get sent to device
 */
static char *udl_set_register(char *buf, u8 reg, u8 val)
{
        *buf++ = 0xAF;
        *buf++ = 0x20;
        *buf++ = reg;
        *buf++ = val;
        return buf;
}

static char *udl_vidreg_lock(char *buf)
{
        return udl_set_register(buf, 0xFF, 0x00);
}

static char *udl_vidreg_unlock(char *buf)
{
        return udl_set_register(buf, 0xFF, 0xFF);
}

static char *udl_set_blank_mode(char *buf, u8 mode)
{
        return udl_set_register(buf, UDL_REG_BLANK_MODE, mode);
}

static char *udl_set_color_depth(char *buf, u8 selection)
{
        return udl_set_register(buf, 0x00, selection);
}

static char *udl_set_base16bpp(char *wrptr, u32 base)
{
        /* the base pointer is 16 bits wide, 0x20 is hi byte. */
        wrptr = udl_set_register(wrptr, 0x20, base >> 16);
        wrptr = udl_set_register(wrptr, 0x21, base >> 8);
        return udl_set_register(wrptr, 0x22, base);
}

/*
 * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
 * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
 */
static char *udl_set_base8bpp(char *wrptr, u32 base)
{
        wrptr = udl_set_register(wrptr, 0x26, base >> 16);
        wrptr = udl_set_register(wrptr, 0x27, base >> 8);
        return udl_set_register(wrptr, 0x28, base);
}

static char *udl_set_register_16(char *wrptr, u8 reg, u16 value)
{
        wrptr = udl_set_register(wrptr, reg, value >> 8);
        return udl_set_register(wrptr, reg+1, value);
}

/*
 * This is kind of weird because the controller takes some
 * register values in a different byte order than other registers.
 */
static char *udl_set_register_16be(char *wrptr, u8 reg, u16 value)
{
        wrptr = udl_set_register(wrptr, reg, value);
        return udl_set_register(wrptr, reg+1, value >> 8);
}

/*
 * LFSR is linear feedback shift register. The reason we have this is
 * because the display controller needs to minimize the clock depth of
 * various counters used in the display path. So this code reverses the
 * provided value into the lfsr16 value by counting backwards to get
 * the value that needs to be set in the hardware comparator to get the
 * same actual count. This makes sense once you read above a couple of
 * times and think about it from a hardware perspective.
 */
static u16 udl_lfsr16(u16 actual_count)
{
        u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */

        while (actual_count--) {
                lv =     ((lv << 1) |
                        (((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
                        & 0xFFFF;
        }

        return (u16) lv;
}

/*
 * This does LFSR conversion on the value that is to be written.
 * See LFSR explanation above for more detail.
 */
static char *udl_set_register_lfsr16(char *wrptr, u8 reg, u16 value)
{
        return udl_set_register_16(wrptr, reg, udl_lfsr16(value));
}

/*
 * This takes a standard fbdev screeninfo struct and all of its monitor mode
 * details and converts them into the DisplayLink equivalent register commands.
  ERR(vreg(dev,               0x00, (color_depth == 16) ? 0 : 1));
  ERR(vreg_lfsr16(dev,        0x01, xDisplayStart));
  ERR(vreg_lfsr16(dev,        0x03, xDisplayEnd));
  ERR(vreg_lfsr16(dev,        0x05, yDisplayStart));
  ERR(vreg_lfsr16(dev,        0x07, yDisplayEnd));
  ERR(vreg_lfsr16(dev,        0x09, xEndCount));
  ERR(vreg_lfsr16(dev,        0x0B, hSyncStart));
  ERR(vreg_lfsr16(dev,        0x0D, hSyncEnd));
  ERR(vreg_big_endian(dev,    0x0F, hPixels));
  ERR(vreg_lfsr16(dev,        0x11, yEndCount));
  ERR(vreg_lfsr16(dev,        0x13, vSyncStart));
  ERR(vreg_lfsr16(dev,        0x15, vSyncEnd));
  ERR(vreg_big_endian(dev,    0x17, vPixels));
  ERR(vreg_little_endian(dev, 0x1B, pixelClock5KHz));

  ERR(vreg(dev,               0x1F, 0));

  ERR(vbuf(dev, WRITE_VIDREG_UNLOCK, DSIZEOF(WRITE_VIDREG_UNLOCK)));
 */
static char *udl_set_vid_cmds(char *wrptr, struct drm_display_mode *mode)
{
        u16 xds, yds;
        u16 xde, yde;
        u16 yec;

        /* x display start */
        xds = mode->crtc_htotal - mode->crtc_hsync_start;
        wrptr = udl_set_register_lfsr16(wrptr, 0x01, xds);
        /* x display end */
        xde = xds + mode->crtc_hdisplay;
        wrptr = udl_set_register_lfsr16(wrptr, 0x03, xde);

        /* y display start */
        yds = mode->crtc_vtotal - mode->crtc_vsync_start;
        wrptr = udl_set_register_lfsr16(wrptr, 0x05, yds);
        /* y display end */
        yde = yds + mode->crtc_vdisplay;
        wrptr = udl_set_register_lfsr16(wrptr, 0x07, yde);

        /* x end count is active + blanking - 1 */
        wrptr = udl_set_register_lfsr16(wrptr, 0x09,
                                        mode->crtc_htotal - 1);

        /* libdlo hardcodes hsync start to 1 */
        wrptr = udl_set_register_lfsr16(wrptr, 0x0B, 1);

        /* hsync end is width of sync pulse + 1 */
        wrptr = udl_set_register_lfsr16(wrptr, 0x0D,
                                        mode->crtc_hsync_end - mode->crtc_hsync_start + 1);

        /* hpixels is active pixels */
        wrptr = udl_set_register_16(wrptr, 0x0F, mode->hdisplay);

        /* yendcount is vertical active + vertical blanking */
        yec = mode->crtc_vtotal;
        wrptr = udl_set_register_lfsr16(wrptr, 0x11, yec);

        /* libdlo hardcodes vsync start to 0 */
        wrptr = udl_set_register_lfsr16(wrptr, 0x13, 0);

        /* vsync end is width of vsync pulse */
        wrptr = udl_set_register_lfsr16(wrptr, 0x15, mode->crtc_vsync_end - mode->crtc_vsync_start);

        /* vpixels is active pixels */
        wrptr = udl_set_register_16(wrptr, 0x17, mode->crtc_vdisplay);

        wrptr = udl_set_register_16be(wrptr, 0x1B,
                                      mode->clock / 5);

        return wrptr;
}

static char *udl_dummy_render(char *wrptr)
{
        *wrptr++ = 0xAF;
        *wrptr++ = 0x6A; /* copy */
        *wrptr++ = 0x00; /* from addr */
        *wrptr++ = 0x00;
        *wrptr++ = 0x00;
        *wrptr++ = 0x01; /* one pixel */
        *wrptr++ = 0x00; /* to address */
        *wrptr++ = 0x00;
        *wrptr++ = 0x00;
        return wrptr;
}

static int udl_crtc_write_mode_to_hw(struct drm_crtc *crtc)
{
        struct drm_device *dev = crtc->dev;
        struct udl_device *udl = to_udl(dev);
        struct urb *urb;
        char *buf;
        int retval;

        if (udl->mode_buf_len == 0) {
                DRM_ERROR("No mode set\n");
                return -EINVAL;
        }

        urb = udl_get_urb(dev);
        if (!urb)
                return -ENOMEM;

        buf = (char *)urb->transfer_buffer;

        memcpy(buf, udl->mode_buf, udl->mode_buf_len);
        retval = udl_submit_urb(dev, urb, udl->mode_buf_len);
        DRM_DEBUG("write mode info %d\n", udl->mode_buf_len);
        return retval;
}

static long udl_log_cpp(unsigned int cpp)
{
        if (WARN_ON(!is_power_of_2(cpp)))
                return -EINVAL;
        return __ffs(cpp);
}

static int udl_aligned_damage_clip(struct drm_rect *clip, int x, int y,
                                   int width, int height)
{
        int x1, x2;

        if (WARN_ON_ONCE(x < 0) ||
            WARN_ON_ONCE(y < 0) ||
            WARN_ON_ONCE(width < 0) ||
            WARN_ON_ONCE(height < 0))
                return -EINVAL;

        x1 = ALIGN_DOWN(x, sizeof(unsigned long));
        x2 = ALIGN(width + (x - x1), sizeof(unsigned long)) + x1;

        clip->x1 = x1;
        clip->y1 = y;
        clip->x2 = x2;
        clip->y2 = y + height;

        return 0;
}

static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
                             int width, int height)
{
        struct drm_device *dev = fb->dev;
        struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;
        int i, ret, tmp_ret;
        char *cmd;
        struct urb *urb;
        struct drm_rect clip;
        int log_bpp;
        void *vaddr;

        ret = udl_log_cpp(fb->format->cpp[0]);
        if (ret < 0)
                return ret;
        log_bpp = ret;

        ret = udl_aligned_damage_clip(&clip, x, y, width, height);
        if (ret)
                return ret;
        else if ((clip.x2 > fb->width) || (clip.y2 > fb->height))
                return -EINVAL;

        if (import_attach) {
                ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
                                               DMA_FROM_DEVICE);
                if (ret)
                        return ret;
        }

        vaddr = drm_gem_shmem_vmap(fb->obj[0]);
        if (IS_ERR(vaddr)) {
                DRM_ERROR("failed to vmap fb\n");
                goto out_dma_buf_end_cpu_access;
        }

        urb = udl_get_urb(dev);
        if (!urb)
                goto out_drm_gem_shmem_vunmap;
        cmd = urb->transfer_buffer;

        for (i = clip.y1; i < clip.y2; i++) {
                const int line_offset = fb->pitches[0] * i;
                const int byte_offset = line_offset + (clip.x1 << log_bpp);
                const int dev_byte_offset = (fb->width * i + clip.x1) << log_bpp;
                const int byte_width = (clip.x2 - clip.x1) << log_bpp;
                ret = udl_render_hline(dev, log_bpp, &urb, (char *)vaddr,
                                       &cmd, byte_offset, dev_byte_offset,
                                       byte_width);
                if (ret)
                        goto out_drm_gem_shmem_vunmap;
        }

        if (cmd > (char *)urb->transfer_buffer) {
                /* Send partial buffer remaining before exiting */
                int len;
                if (cmd < (char *)urb->transfer_buffer + urb->transfer_buffer_length)
                        *cmd++ = 0xAF;
                len = cmd - (char *)urb->transfer_buffer;
                ret = udl_submit_urb(dev, urb, len);
        } else {
                udl_urb_completion(urb);
        }

        ret = 0;

out_drm_gem_shmem_vunmap:
        drm_gem_shmem_vunmap(fb->obj[0], vaddr);
out_dma_buf_end_cpu_access:
        if (import_attach) {
                tmp_ret = dma_buf_end_cpu_access(import_attach->dmabuf,
                                                 DMA_FROM_DEVICE);
                if (tmp_ret && !ret)
                        ret = tmp_ret; /* only update ret if not set yet */
        }

        return ret;
}

/*
 * Simple display pipeline
 */

static const uint32_t udl_simple_display_pipe_formats[] = {
        DRM_FORMAT_RGB565,
        DRM_FORMAT_XRGB8888,
};

static enum drm_mode_status
udl_simple_display_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
                                   const struct drm_display_mode *mode)
{
        return MODE_OK;
}

static void
udl_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
                               struct drm_crtc_state *crtc_state,
                               struct drm_plane_state *plane_state)
{
        struct drm_crtc *crtc = &pipe->crtc;
        struct drm_device *dev = crtc->dev;
        struct drm_framebuffer *fb = plane_state->fb;
        struct udl_device *udl = to_udl(dev);
        struct drm_display_mode *mode = &crtc_state->mode;
        char *buf;
        char *wrptr;
        int color_depth = UDL_COLOR_DEPTH_16BPP;

        buf = (char *)udl->mode_buf;

        /* This first section has to do with setting the base address on the
         * controller associated with the display. There are 2 base
         * pointers, currently, we only use the 16 bpp segment.
         */
        wrptr = udl_vidreg_lock(buf);
        wrptr = udl_set_color_depth(wrptr, color_depth);
        /* set base for 16bpp segment to 0 */
        wrptr = udl_set_base16bpp(wrptr, 0);
        /* set base for 8bpp segment to end of fb */
        wrptr = udl_set_base8bpp(wrptr, 2 * mode->vdisplay * mode->hdisplay);

        wrptr = udl_set_vid_cmds(wrptr, mode);
        wrptr = udl_set_blank_mode(wrptr, UDL_BLANK_MODE_ON);
        wrptr = udl_vidreg_unlock(wrptr);

        wrptr = udl_dummy_render(wrptr);

        udl->mode_buf_len = wrptr - buf;

        udl_handle_damage(fb, 0, 0, fb->width, fb->height);

        if (!crtc_state->mode_changed)
                return;

        /* enable display */
        udl_crtc_write_mode_to_hw(crtc);
}

static void
udl_simple_display_pipe_disable(struct drm_simple_display_pipe *pipe)
{
        struct drm_crtc *crtc = &pipe->crtc;
        struct drm_device *dev = crtc->dev;
        struct urb *urb;
        char *buf;

        urb = udl_get_urb(dev);
        if (!urb)
                return;

        buf = (char *)urb->transfer_buffer;
        buf = udl_vidreg_lock(buf);
        buf = udl_set_blank_mode(buf, UDL_BLANK_MODE_POWERDOWN);
        buf = udl_vidreg_unlock(buf);
        buf = udl_dummy_render(buf);

        udl_submit_urb(dev, urb, buf - (char *)urb->transfer_buffer);
}

static void
udl_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
                               struct drm_plane_state *old_plane_state)
{
        struct drm_plane_state *state = pipe->plane.state;
        struct drm_framebuffer *fb = state->fb;
        struct drm_rect rect;

        if (!fb)
                return;

        if (drm_atomic_helper_damage_merged(old_plane_state, state, &rect))
                udl_handle_damage(fb, rect.x1, rect.y1, rect.x2 - rect.x1,
                                  rect.y2 - rect.y1);
}

static const
struct drm_simple_display_pipe_funcs udl_simple_display_pipe_funcs = {
        .mode_valid = udl_simple_display_pipe_mode_valid,
        .enable = udl_simple_display_pipe_enable,
        .disable = udl_simple_display_pipe_disable,
        .update = udl_simple_display_pipe_update,
        .prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
};

/*
 * Modesetting
 */

static const struct drm_mode_config_funcs udl_mode_funcs = {
        .fb_create = drm_gem_fb_create_with_dirty,
        .atomic_check  = drm_atomic_helper_check,
        .atomic_commit = drm_atomic_helper_commit,
};

int udl_modeset_init(struct drm_device *dev)
{
        size_t format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);
        struct udl_device *udl = to_udl(dev);
        struct drm_connector *connector;
        int ret;

        ret = drmm_mode_config_init(dev);
        if (ret)
                return ret;

        dev->mode_config.min_width = 640;
        dev->mode_config.min_height = 480;

        dev->mode_config.max_width = 2048;
        dev->mode_config.max_height = 2048;

        dev->mode_config.prefer_shadow = 0;
        dev->mode_config.preferred_depth = 16;

        dev->mode_config.funcs = &udl_mode_funcs;

        connector = udl_connector_init(dev);
        if (IS_ERR(connector))
                return PTR_ERR(connector);

        format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);

        ret = drm_simple_display_pipe_init(dev, &udl->display_pipe,
                                           &udl_simple_display_pipe_funcs,
                                           udl_simple_display_pipe_formats,
                                           format_count, NULL, connector);
        if (ret)
                return ret;

        drm_mode_config_reset(dev);

        return 0;
}