// SPDX-License-Identifier: GPL-2.0+

#include <linux/crc32.h>

#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_vblank.h>

#include "vkms_drv.h"

static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
                                 const struct vkms_composer *composer)
{
        u32 pixel;
        int src_offset = composer->offset + (y * composer->pitch)
                                      + (x * composer->cpp);

        pixel = *(u32 *)&buffer[src_offset];

        return pixel;
}

/**
 * compute_crc - Compute CRC value on output frame
 *
 * @vaddr: address to final framebuffer
 * @composer: framebuffer's metadata
 *
 * returns CRC value computed using crc32 on the visible portion of
 * the final framebuffer at vaddr_out
 */
static uint32_t compute_crc(const u8 *vaddr,
                            const struct vkms_composer *composer)
{
        int x, y;
        u32 crc = 0, pixel = 0;
        int x_src = composer->src.x1 >> 16;
        int y_src = composer->src.y1 >> 16;
        int h_src = drm_rect_height(&composer->src) >> 16;
        int w_src = drm_rect_width(&composer->src) >> 16;

        for (y = y_src; y < y_src + h_src; ++y) {
                for (x = x_src; x < x_src + w_src; ++x) {
                        pixel = get_pixel_from_buffer(x, y, vaddr, composer);
                        crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
                }
        }

        return crc;
}

static u8 blend_channel(u8 src, u8 dst, u8 alpha)
{
        u32 pre_blend;
        u8 new_color;

        pre_blend = (src * 255 + dst * (255 - alpha));

        /* Faster div by 255 */
        new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8);

        return new_color;
}

/**
 * alpha_blend - alpha blending equation
 * @argb_src: src pixel on premultiplied alpha mode
 * @argb_dst: dst pixel completely opaque
 *
 * blend pixels using premultiplied blend formula. The current DRM assumption
 * is that pixel color values have been already pre-multiplied with the alpha
 * channel values. See more drm_plane_create_blend_mode_property(). Also, this
 * formula assumes a completely opaque background.
 */
static void alpha_blend(const u8 *argb_src, u8 *argb_dst)
{
        u8 alpha;

        alpha = argb_src[3];
        argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], alpha);
        argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], alpha);
        argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], alpha);
}

/**
 * x_blend - blending equation that ignores the pixel alpha
 *
 * overwrites RGB color value from src pixel to dst pixel.
 */
static void x_blend(const u8 *xrgb_src, u8 *xrgb_dst)
{
        memcpy(xrgb_dst, xrgb_src, sizeof(u8) * 3);
}

/**
 * blend - blend value at vaddr_src with value at vaddr_dst
 * @vaddr_dst: destination address
 * @vaddr_src: source address
 * @dst_composer: destination framebuffer's metadata
 * @src_composer: source framebuffer's metadata
 * @pixel_blend: blending equation based on plane format
 *
 * Blend the vaddr_src value with the vaddr_dst value using a pixel blend
 * equation according to the supported plane formats DRM_FORMAT_(A/XRGB8888)
 * and clearing alpha channel to an completely opaque background. This function
 * uses buffer's metadata to locate the new composite values at vaddr_dst.
 *
 * TODO: completely clear the primary plane (a = 0xff) before starting to blend
 * pixel color values
 */
static void blend(void *vaddr_dst, void *vaddr_src,
                  struct vkms_composer *dst_composer,
                  struct vkms_composer *src_composer,
                  void (*pixel_blend)(const u8 *, u8 *))
{
        int i, j, j_dst, i_dst;
        int offset_src, offset_dst;
        u8 *pixel_dst, *pixel_src;

        int x_src = src_composer->src.x1 >> 16;
        int y_src = src_composer->src.y1 >> 16;

        int x_dst = src_composer->dst.x1;
        int y_dst = src_composer->dst.y1;
        int h_dst = drm_rect_height(&src_composer->dst);
        int w_dst = drm_rect_width(&src_composer->dst);

        int y_limit = y_src + h_dst;
        int x_limit = x_src + w_dst;

        for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
                for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
                        offset_dst = dst_composer->offset
                                     + (i_dst * dst_composer->pitch)
                                     + (j_dst++ * dst_composer->cpp);
                        offset_src = src_composer->offset
                                     + (i * src_composer->pitch)
                                     + (j * src_composer->cpp);

                        pixel_src = (u8 *)(vaddr_src + offset_src);
                        pixel_dst = (u8 *)(vaddr_dst + offset_dst);
                        pixel_blend(pixel_src, pixel_dst);
                        /* clearing alpha channel (0xff)*/
                        pixel_dst[3] = 0xff;
                }
                i_dst++;
        }
}

static void compose_plane(struct vkms_composer *primary_composer,
                          struct vkms_composer *plane_composer,
                          void *vaddr_out)
{
        struct drm_gem_object *plane_obj;
        struct drm_gem_shmem_object *plane_shmem_obj;
        struct drm_framebuffer *fb = &plane_composer->fb;
        void (*pixel_blend)(const u8 *p_src, u8 *p_dst);

        plane_obj = drm_gem_fb_get_obj(&plane_composer->fb, 0);
        plane_shmem_obj = to_drm_gem_shmem_obj(plane_obj);

        if (WARN_ON(!plane_shmem_obj->vaddr))
                return;

        if (fb->format->format == DRM_FORMAT_ARGB8888)
                pixel_blend = &alpha_blend;
        else
                pixel_blend = &x_blend;

        blend(vaddr_out, plane_shmem_obj->vaddr, primary_composer,
              plane_composer, pixel_blend);
}

static int compose_active_planes(void **vaddr_out,
                                 struct vkms_composer *primary_composer,
                                 struct vkms_crtc_state *crtc_state)
{
        struct drm_framebuffer *fb = &primary_composer->fb;
        struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
        struct drm_gem_shmem_object *shmem_obj = to_drm_gem_shmem_obj(gem_obj);
        int i;

        if (!*vaddr_out) {
                *vaddr_out = kzalloc(shmem_obj->base.size, GFP_KERNEL);
                if (!*vaddr_out) {
                        DRM_ERROR("Cannot allocate memory for output frame.");
                        return -ENOMEM;
                }
        }

        if (WARN_ON(!shmem_obj->vaddr))
                return -EINVAL;

        memcpy(*vaddr_out, shmem_obj->vaddr, shmem_obj->base.size);

        /* If there are other planes besides primary, we consider the active
         * planes should be in z-order and compose them associatively:
         * ((primary <- overlay) <- cursor)
         */
        for (i = 1; i < crtc_state->num_active_planes; i++)
                compose_plane(primary_composer,
                              crtc_state->active_planes[i]->composer,
                              *vaddr_out);

        return 0;
}

/**
 * vkms_composer_worker - ordered work_struct to compute CRC
 *
 * @work: work_struct
 *
 * Work handler for composing and computing CRCs. work_struct scheduled in
 * an ordered workqueue that's periodically scheduled to run by
 * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state().
 */
void vkms_composer_worker(struct work_struct *work)
{
        struct vkms_crtc_state *crtc_state = container_of(work,
                                                struct vkms_crtc_state,
                                                composer_work);
        struct drm_crtc *crtc = crtc_state->base.crtc;
        struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
        struct vkms_composer *primary_composer = NULL;
        struct vkms_plane_state *act_plane = NULL;
        bool crc_pending, wb_pending;
        void *vaddr_out = NULL;
        u32 crc32 = 0;
        u64 frame_start, frame_end;
        int ret;

        spin_lock_irq(&out->composer_lock);
        frame_start = crtc_state->frame_start;
        frame_end = crtc_state->frame_end;
        crc_pending = crtc_state->crc_pending;
        wb_pending = crtc_state->wb_pending;
        crtc_state->frame_start = 0;
        crtc_state->frame_end = 0;
        crtc_state->crc_pending = false;
        spin_unlock_irq(&out->composer_lock);

        /*
         * We raced with the vblank hrtimer and previous work already computed
         * the crc, nothing to do.
         */
        if (!crc_pending)
                return;

        if (crtc_state->num_active_planes >= 1) {
                act_plane = crtc_state->active_planes[0];
                if (act_plane->base.plane->type == DRM_PLANE_TYPE_PRIMARY)
                        primary_composer = act_plane->composer;
        }

        if (!primary_composer)
                return;

        if (wb_pending)
                vaddr_out = crtc_state->active_writeback;

        ret = compose_active_planes(&vaddr_out, primary_composer,
                                    crtc_state);
        if (ret) {
                if (ret == -EINVAL && !wb_pending)
                        kfree(vaddr_out);
                return;
        }

        crc32 = compute_crc(vaddr_out, primary_composer);

        if (wb_pending) {
                drm_writeback_signal_completion(&out->wb_connector, 0);
                spin_lock_irq(&out->composer_lock);
                crtc_state->wb_pending = false;
                spin_unlock_irq(&out->composer_lock);
        } else {
                kfree(vaddr_out);
        }

        /*
         * The worker can fall behind the vblank hrtimer, make sure we catch up.
         */
        while (frame_start <= frame_end)
                drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
}

static const char * const pipe_crc_sources[] = {"auto"};

const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
                                        size_t *count)
{
        *count = ARRAY_SIZE(pipe_crc_sources);
        return pipe_crc_sources;
}

static int vkms_crc_parse_source(const char *src_name, bool *enabled)
{
        int ret = 0;

        if (!src_name) {
                *enabled = false;
        } else if (strcmp(src_name, "auto") == 0) {
                *enabled = true;
        } else {
                *enabled = false;
                ret = -EINVAL;
        }

        return ret;
}

int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
                           size_t *values_cnt)
{
        bool enabled;

        if (vkms_crc_parse_source(src_name, &enabled) < 0) {
                DRM_DEBUG_DRIVER("unknown source %s\n", src_name);
                return -EINVAL;
        }

        *values_cnt = 1;

        return 0;
}

void vkms_set_composer(struct vkms_output *out, bool enabled)
{
        bool old_enabled;

        if (enabled)
                drm_crtc_vblank_get(&out->crtc);

        spin_lock_irq(&out->lock);
        old_enabled = out->composer_enabled;
        out->composer_enabled = enabled;
        spin_unlock_irq(&out->lock);

        if (old_enabled)
                drm_crtc_vblank_put(&out->crtc);
}

int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
{
        struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
        bool enabled = false;
        int ret = 0;

        ret = vkms_crc_parse_source(src_name, &enabled);

        vkms_set_composer(out, enabled);

        return ret;
}