// SPDX-License-Identifier: MIT

#include <linux/export.h>
#include <linux/moduleparam.h>
#include <linux/vmalloc.h>

#include <drm/drm_crtc_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem.h>
#include <drm/drm_print.h>

#include <drm/drm_fbdev_ttm.h>

/* @user: 1=userspace, 0=fbcon */
static int drm_fbdev_ttm_fb_open(struct fb_info *info, int user)
{
 struct drm_fb_helper *fb_helper = info->par;

 /* No need to take a ref for fbcon because it unbinds on unregister */
 if (user && !try_module_get(fb_helper->dev->driver->fops->owner))
  return -ENODEV;

 return 0;
}

static int drm_fbdev_ttm_fb_release(struct fb_info *info, int user)
{
 struct drm_fb_helper *fb_helper = info->par;

 if (user)
  module_put(fb_helper->dev->driver->fops->owner);

 return 0;
}

FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_ttm,
       drm_fb_helper_damage_range,
       drm_fb_helper_damage_area);

static void drm_fbdev_ttm_fb_destroy(struct fb_info *info)
{
 struct drm_fb_helper *fb_helper = info->par;
 void *shadow = info->screen_buffer;

 if (!fb_helper->dev)
  return;

 fb_deferred_io_cleanup(info);
 drm_fb_helper_fini(fb_helper);
 vfree(shadow);
 drm_client_framebuffer_delete(fb_helper->buffer);

 drm_client_release(&fb_helper->client);
 drm_fb_helper_unprepare(fb_helper);
 kfree(fb_helper);
}

static const struct fb_ops drm_fbdev_ttm_fb_ops = {
 .owner  = THIS_MODULE,
 .fb_open = drm_fbdev_ttm_fb_open,
 .fb_release = drm_fbdev_ttm_fb_release,
 FB_DEFAULT_DEFERRED_OPS(drm_fbdev_ttm),
 DRM_FB_HELPER_DEFAULT_OPS,
 .fb_destroy = drm_fbdev_ttm_fb_destroy,
};

static void drm_fbdev_ttm_damage_blit_real(struct drm_fb_helper *fb_helper,
        struct drm_clip_rect *clip,
        struct iosys_map *dst)
{
 struct drm_framebuffer *fb = fb_helper->fb;
 size_t offset = clip->y1 * fb->pitches[0];
 size_t len = clip->x2 - clip->x1;
 unsigned int y;
 void *src;

 switch (drm_format_info_bpp(fb->format, 0)) {
 case 1:
  offset += clip->x1 / 8;
  len = DIV_ROUND_UP(len + clip->x1 % 8, 8);
  break;
 case 2:
  offset += clip->x1 / 4;
  len = DIV_ROUND_UP(len + clip->x1 % 4, 4);
  break;
 case 4:
  offset += clip->x1 / 2;
  len = DIV_ROUND_UP(len + clip->x1 % 2, 2);
  break;
 default:
  offset += clip->x1 * fb->format->cpp[0];
  len *= fb->format->cpp[0];
  break;
 }

 src = fb_helper->info->screen_buffer + offset;
 iosys_map_incr(dst, offset); /* go to first pixel within clip rect */

 for (y = clip->y1; y < clip->y2; y++) {
  iosys_map_memcpy_to(dst, 0, src, len);
  iosys_map_incr(dst, fb->pitches[0]);
  src += fb->pitches[0];
 }
}

static int drm_fbdev_ttm_damage_blit(struct drm_fb_helper *fb_helper,
         struct drm_clip_rect *clip)
{
 struct drm_client_buffer *buffer = fb_helper->buffer;
 struct iosys_map map, dst;
 int ret;

 /*
 * We have to pin the client buffer to its current location while
 * flushing the shadow buffer. In the general case, concurrent
 * modesetting operations could try to move the buffer and would
 * fail. The modeset has to be serialized by acquiring the reservation
 * object of the underlying BO here.
 *
 * For fbdev emulation, we only have to protect against fbdev modeset
 * operations. Nothing else will involve the client buffer's BO. So it
 * is sufficient to acquire struct drm_fb_helper.lock here.
 */
 mutex_lock(&fb_helper->lock);

 ret = drm_client_buffer_vmap_local(buffer, &map);
 if (ret)
  goto out;

 dst = map;
 drm_fbdev_ttm_damage_blit_real(fb_helper, clip, &dst);

 drm_client_buffer_vunmap_local(buffer);

out:
 mutex_unlock(&fb_helper->lock);

 return ret;
}

static int drm_fbdev_ttm_helper_fb_dirty(struct drm_fb_helper *helper,
      struct drm_clip_rect *clip)
{
 struct drm_device *dev = helper->dev;
 int ret;

 /* Call damage handlers only if necessary */
 if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
  return 0;

 ret = drm_fbdev_ttm_damage_blit(helper, clip);
 if (drm_WARN_ONCE(dev, ret, "Damage blitter failed: ret=%d\n", ret))
  return ret;

 if (helper->fb->funcs->dirty) {
  ret = helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
  if (drm_WARN_ONCE(dev, ret, "Dirty helper failed: ret=%d\n", ret))
   return ret;
 }

 return 0;
}

static const struct drm_fb_helper_funcs drm_fbdev_ttm_helper_funcs = {
 .fb_dirty = drm_fbdev_ttm_helper_fb_dirty,
};

/*
 * struct drm_driver
 */

int drm_fbdev_ttm_driver_fbdev_probe(struct drm_fb_helper *fb_helper,
         struct drm_fb_helper_surface_size *sizes)
{
 struct drm_client_dev *client = &fb_helper->client;
 struct drm_device *dev = fb_helper->dev;
 struct drm_client_buffer *buffer;
 struct fb_info *info;
 size_t screen_size;
 void *screen_buffer;
 u32 format;
 int ret;

 drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
      sizes->surface_width, sizes->surface_height,
      sizes->surface_bpp);

 format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp,
          sizes->surface_depth);
 buffer = drm_client_framebuffer_create(client, sizes->surface_width,
            sizes->surface_height, format);
 if (IS_ERR(buffer))
  return PTR_ERR(buffer);

 fb_helper->funcs = &drm_fbdev_ttm_helper_funcs;
 fb_helper->buffer = buffer;
 fb_helper->fb = buffer->fb;

 screen_size = buffer->gem->size;
 screen_buffer = vzalloc(screen_size);
 if (!screen_buffer) {
  ret = -ENOMEM;
  goto err_drm_client_framebuffer_delete;
 }

 info = drm_fb_helper_alloc_info(fb_helper);
 if (IS_ERR(info)) {
  ret = PTR_ERR(info);
  goto err_vfree;
 }

 drm_fb_helper_fill_info(info, fb_helper, sizes);

 info->fbops = &drm_fbdev_ttm_fb_ops;

 /* screen */
 info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
 info->screen_buffer = screen_buffer;
 info->fix.smem_len = screen_size;

 /* deferred I/O */
 fb_helper->fbdefio.delay = HZ / 20;
 fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;

 info->fbdefio = &fb_helper->fbdefio;
 ret = fb_deferred_io_init(info);
 if (ret)
  goto err_drm_fb_helper_release_info;

 return 0;

err_drm_fb_helper_release_info:
 drm_fb_helper_release_info(fb_helper);
err_vfree:
 vfree(screen_buffer);
err_drm_client_framebuffer_delete:
 fb_helper->fb = NULL;
 fb_helper->buffer = NULL;
 drm_client_framebuffer_delete(buffer);
 return ret;
}
EXPORT_SYMBOL(drm_fbdev_ttm_driver_fbdev_probe);