// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2015 Free Electrons
 * Copyright (C) 2015 NextThing Co
 *
 * Maxime Ripard <maxime.ripard@free-electrons.com>
 */

#include <linux/component.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/of_graph.h>
#include <linux/dma-mapping.h>
#include <linux/platform_device.h>
#include <linux/reset.h>

#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_crtc.h>
#include <drm/drm_fb_cma_helper.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_gem_cma_helper.h>
#include <drm/drm_plane_helper.h>
#include <drm/drm_probe_helper.h>

#include "sun4i_backend.h"
#include "sun4i_drv.h"
#include "sun4i_frontend.h"
#include "sun4i_layer.h"
#include "sunxi_engine.h"

struct sun4i_backend_quirks {
        /* backend <-> TCON muxing selection done in backend */
        bool needs_output_muxing;

        /* alpha at the lowest z position is not always supported */
        bool supports_lowest_plane_alpha;
};

static const u32 sunxi_rgb2yuv_coef[12] = {
        0x00000107, 0x00000204, 0x00000064, 0x00000108,
        0x00003f69, 0x00003ed6, 0x000001c1, 0x00000808,
        0x000001c1, 0x00003e88, 0x00003fb8, 0x00000808
};

static void sun4i_backend_apply_color_correction(struct sunxi_engine *engine)
{
        int i;

        DRM_DEBUG_DRIVER("Applying RGB to YUV color correction\n");

        /* Set color correction */
        regmap_write(engine->regs, SUN4I_BACKEND_OCCTL_REG,
                     SUN4I_BACKEND_OCCTL_ENABLE);

        for (i = 0; i < 12; i++)
                regmap_write(engine->regs, SUN4I_BACKEND_OCRCOEF_REG(i),
                             sunxi_rgb2yuv_coef[i]);
}

static void sun4i_backend_disable_color_correction(struct sunxi_engine *engine)
{
        DRM_DEBUG_DRIVER("Disabling color correction\n");

        /* Disable color correction */
        regmap_update_bits(engine->regs, SUN4I_BACKEND_OCCTL_REG,
                           SUN4I_BACKEND_OCCTL_ENABLE, 0);
}

static void sun4i_backend_commit(struct sunxi_engine *engine)
{
        DRM_DEBUG_DRIVER("Committing changes\n");

        regmap_write(engine->regs, SUN4I_BACKEND_REGBUFFCTL_REG,
                     SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS |
                     SUN4I_BACKEND_REGBUFFCTL_LOADCTL);
}

void sun4i_backend_layer_enable(struct sun4i_backend *backend,
                                int layer, bool enable)
{
        u32 val;

        DRM_DEBUG_DRIVER("%sabling layer %d\n", enable ? "En" : "Dis",
                         layer);

        if (enable)
                val = SUN4I_BACKEND_MODCTL_LAY_EN(layer);
        else
                val = 0;

        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
                           SUN4I_BACKEND_MODCTL_LAY_EN(layer), val);
}

static int sun4i_backend_drm_format_to_layer(u32 format, u32 *mode)
{
        switch (format) {
        case DRM_FORMAT_ARGB8888:
                *mode = SUN4I_BACKEND_LAY_FBFMT_ARGB8888;
                break;

        case DRM_FORMAT_ARGB4444:
                *mode = SUN4I_BACKEND_LAY_FBFMT_ARGB4444;
                break;

        case DRM_FORMAT_ARGB1555:
                *mode = SUN4I_BACKEND_LAY_FBFMT_ARGB1555;
                break;

        case DRM_FORMAT_RGBA5551:
                *mode = SUN4I_BACKEND_LAY_FBFMT_RGBA5551;
                break;

        case DRM_FORMAT_RGBA4444:
                *mode = SUN4I_BACKEND_LAY_FBFMT_RGBA4444;
                break;

        case DRM_FORMAT_XRGB8888:
                *mode = SUN4I_BACKEND_LAY_FBFMT_XRGB8888;
                break;

        case DRM_FORMAT_RGB888:
                *mode = SUN4I_BACKEND_LAY_FBFMT_RGB888;
                break;

        case DRM_FORMAT_RGB565:
                *mode = SUN4I_BACKEND_LAY_FBFMT_RGB565;
                break;

        default:
                return -EINVAL;
        }

        return 0;
}

static const uint32_t sun4i_backend_formats[] = {
        DRM_FORMAT_ARGB1555,
        DRM_FORMAT_ARGB4444,
        DRM_FORMAT_ARGB8888,
        DRM_FORMAT_RGB565,
        DRM_FORMAT_RGB888,
        DRM_FORMAT_RGBA4444,
        DRM_FORMAT_RGBA5551,
        DRM_FORMAT_UYVY,
        DRM_FORMAT_VYUY,
        DRM_FORMAT_XRGB8888,
        DRM_FORMAT_YUYV,
        DRM_FORMAT_YVYU,
};

bool sun4i_backend_format_is_supported(uint32_t fmt, uint64_t modifier)
{
        unsigned int i;

        if (modifier != DRM_FORMAT_MOD_LINEAR)
                return false;

        for (i = 0; i < ARRAY_SIZE(sun4i_backend_formats); i++)
                if (sun4i_backend_formats[i] == fmt)
                        return true;

        return false;
}

int sun4i_backend_update_layer_coord(struct sun4i_backend *backend,
                                     int layer, struct drm_plane *plane)
{
        struct drm_plane_state *state = plane->state;

        DRM_DEBUG_DRIVER("Updating layer %d\n", layer);

        if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
                DRM_DEBUG_DRIVER("Primary layer, updating global size W: %u H: %u\n",
                                 state->crtc_w, state->crtc_h);
                regmap_write(backend->engine.regs, SUN4I_BACKEND_DISSIZE_REG,
                             SUN4I_BACKEND_DISSIZE(state->crtc_w,
                                                   state->crtc_h));
        }

        /* Set height and width */
        DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n",
                         state->crtc_w, state->crtc_h);
        regmap_write(backend->engine.regs, SUN4I_BACKEND_LAYSIZE_REG(layer),
                     SUN4I_BACKEND_LAYSIZE(state->crtc_w,
                                           state->crtc_h));

        /* Set base coordinates */
        DRM_DEBUG_DRIVER("Layer coordinates X: %d Y: %d\n",
                         state->crtc_x, state->crtc_y);
        regmap_write(backend->engine.regs, SUN4I_BACKEND_LAYCOOR_REG(layer),
                     SUN4I_BACKEND_LAYCOOR(state->crtc_x,
                                           state->crtc_y));

        return 0;
}

static int sun4i_backend_update_yuv_format(struct sun4i_backend *backend,
                                           int layer, struct drm_plane *plane)
{
        struct drm_plane_state *state = plane->state;
        struct drm_framebuffer *fb = state->fb;
        const struct drm_format_info *format = fb->format;
        const uint32_t fmt = format->format;
        u32 val = SUN4I_BACKEND_IYUVCTL_EN;
        int i;

        for (i = 0; i < ARRAY_SIZE(sunxi_bt601_yuv2rgb_coef); i++)
                regmap_write(backend->engine.regs,
                             SUN4I_BACKEND_YGCOEF_REG(i),
                             sunxi_bt601_yuv2rgb_coef[i]);

        /*
         * We should do that only for a single plane, but the
         * framebuffer's atomic_check has our back on this.
         */
        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN,
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN);

        /* TODO: Add support for the multi-planar YUV formats */
        if (drm_format_info_is_yuv_packed(format) &&
            drm_format_info_is_yuv_sampling_422(format))
                val |= SUN4I_BACKEND_IYUVCTL_FBFMT_PACKED_YUV422;
        else
                DRM_DEBUG_DRIVER("Unsupported YUV format (0x%x)\n", fmt);

        /*
         * Allwinner seems to list the pixel sequence from right to left, while
         * DRM lists it from left to right.
         */
        switch (fmt) {
        case DRM_FORMAT_YUYV:
                val |= SUN4I_BACKEND_IYUVCTL_FBPS_VYUY;
                break;
        case DRM_FORMAT_YVYU:
                val |= SUN4I_BACKEND_IYUVCTL_FBPS_UYVY;
                break;
        case DRM_FORMAT_UYVY:
                val |= SUN4I_BACKEND_IYUVCTL_FBPS_YVYU;
                break;
        case DRM_FORMAT_VYUY:
                val |= SUN4I_BACKEND_IYUVCTL_FBPS_YUYV;
                break;
        default:
                DRM_DEBUG_DRIVER("Unsupported YUV pixel sequence (0x%x)\n",
                                 fmt);
        }

        regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVCTL_REG, val);

        return 0;
}

int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
                                       int layer, struct drm_plane *plane)
{
        struct drm_plane_state *state = plane->state;
        struct drm_framebuffer *fb = state->fb;
        bool interlaced = false;
        u32 val;
        int ret;

        /* Clear the YUV mode */
        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN, 0);

        if (plane->state->crtc)
                interlaced = plane->state->crtc->state->adjusted_mode.flags
                        & DRM_MODE_FLAG_INTERLACE;

        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
                           SUN4I_BACKEND_MODCTL_ITLMOD_EN,
                           interlaced ? SUN4I_BACKEND_MODCTL_ITLMOD_EN : 0);

        DRM_DEBUG_DRIVER("Switching display backend interlaced mode %s\n",
                         interlaced ? "on" : "off");

        val = SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA(state->alpha >> 8);
        if (state->alpha != DRM_BLEND_ALPHA_OPAQUE)
                val |= SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN;
        regmap_update_bits(backend->engine.regs,
                           SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_MASK |
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN,
                           val);

        if (fb->format->is_yuv)
                return sun4i_backend_update_yuv_format(backend, layer, plane);

        ret = sun4i_backend_drm_format_to_layer(fb->format->format, &val);
        if (ret) {
                DRM_DEBUG_DRIVER("Invalid format\n");
                return ret;
        }

        regmap_update_bits(backend->engine.regs,
                           SUN4I_BACKEND_ATTCTL_REG1(layer),
                           SUN4I_BACKEND_ATTCTL_REG1_LAY_FBFMT, val);

        return 0;
}

int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
                                        int layer, uint32_t fmt)
{
        u32 val;
        int ret;

        ret = sun4i_backend_drm_format_to_layer(fmt, &val);
        if (ret) {
                DRM_DEBUG_DRIVER("Invalid format\n");
                return ret;
        }

        regmap_update_bits(backend->engine.regs,
                           SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN,
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN);

        regmap_update_bits(backend->engine.regs,
                           SUN4I_BACKEND_ATTCTL_REG1(layer),
                           SUN4I_BACKEND_ATTCTL_REG1_LAY_FBFMT, val);

        return 0;
}

static int sun4i_backend_update_yuv_buffer(struct sun4i_backend *backend,
                                           struct drm_framebuffer *fb,
                                           dma_addr_t paddr)
{
        /* TODO: Add support for the multi-planar YUV formats */
        DRM_DEBUG_DRIVER("Setting packed YUV buffer address to %pad\n", &paddr);
        regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVADD_REG(0), paddr);

        DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
        regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVLINEWIDTH_REG(0),
                     fb->pitches[0] * 8);

        return 0;
}

int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
                                      int layer, struct drm_plane *plane)
{
        struct drm_plane_state *state = plane->state;
        struct drm_framebuffer *fb = state->fb;
        u32 lo_paddr, hi_paddr;
        dma_addr_t paddr;

        /* Set the line width */
        DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
        regmap_write(backend->engine.regs,
                     SUN4I_BACKEND_LAYLINEWIDTH_REG(layer),
                     fb->pitches[0] * 8);

        /* Get the start of the displayed memory */
        paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
        DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);

        if (fb->format->is_yuv)
                return sun4i_backend_update_yuv_buffer(backend, fb, paddr);

        /* Write the 32 lower bits of the address (in bits) */
        lo_paddr = paddr << 3;
        DRM_DEBUG_DRIVER("Setting address lower bits to 0x%x\n", lo_paddr);
        regmap_write(backend->engine.regs,
                     SUN4I_BACKEND_LAYFB_L32ADD_REG(layer),
                     lo_paddr);

        /* And the upper bits */
        hi_paddr = paddr >> 29;
        DRM_DEBUG_DRIVER("Setting address high bits to 0x%x\n", hi_paddr);
        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_LAYFB_H4ADD_REG,
                           SUN4I_BACKEND_LAYFB_H4ADD_MSK(layer),
                           SUN4I_BACKEND_LAYFB_H4ADD(layer, hi_paddr));

        return 0;
}

int sun4i_backend_update_layer_zpos(struct sun4i_backend *backend, int layer,
                                    struct drm_plane *plane)
{
        struct drm_plane_state *state = plane->state;
        struct sun4i_layer_state *p_state = state_to_sun4i_layer_state(state);
        unsigned int priority = state->normalized_zpos;
        unsigned int pipe = p_state->pipe;

        DRM_DEBUG_DRIVER("Setting layer %d's priority to %d and pipe %d\n",
                         layer, priority, pipe);
        regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL_MASK |
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK,
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(p_state->pipe) |
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(priority));

        return 0;
}

void sun4i_backend_cleanup_layer(struct sun4i_backend *backend,
                                 int layer)
{
        regmap_update_bits(backend->engine.regs,
                           SUN4I_BACKEND_ATTCTL_REG0(layer),
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN |
                           SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN, 0);
}

static bool sun4i_backend_plane_uses_scaler(struct drm_plane_state *state)
{
        u16 src_h = state->src_h >> 16;
        u16 src_w = state->src_w >> 16;

        DRM_DEBUG_DRIVER("Input size %dx%d, output size %dx%d\n",
                         src_w, src_h, state->crtc_w, state->crtc_h);

        if ((state->crtc_h != src_h) || (state->crtc_w != src_w))
                return true;

        return false;
}

static bool sun4i_backend_plane_uses_frontend(struct drm_plane_state *state)
{
        struct sun4i_layer *layer = plane_to_sun4i_layer(state->plane);
        struct sun4i_backend *backend = layer->backend;
        uint32_t format = state->fb->format->format;
        uint64_t modifier = state->fb->modifier;

        if (IS_ERR(backend->frontend))
                return false;

        if (!sun4i_frontend_format_is_supported(format, modifier))
                return false;

        if (!sun4i_backend_format_is_supported(format, modifier))
                return true;

        /*
         * TODO: The backend alone allows 2x and 4x integer scaling, including
         * support for an alpha component (which the frontend doesn't support).
         * Use the backend directly instead of the frontend in this case, with
         * another test to return false.
         */

        if (sun4i_backend_plane_uses_scaler(state))
                return true;

        /*
         * Here the format is supported by both the frontend and the backend
         * and no frontend scaling is required, so use the backend directly.
         */
        return false;
}

static bool sun4i_backend_plane_is_supported(struct drm_plane_state *state,
                                             bool *uses_frontend)
{
        if (sun4i_backend_plane_uses_frontend(state)) {
                *uses_frontend = true;
                return true;
        }

        *uses_frontend = false;

        /* Scaling is not supported without the frontend. */
        if (sun4i_backend_plane_uses_scaler(state))
                return false;

        return true;
}

static void sun4i_backend_atomic_begin(struct sunxi_engine *engine,
                                       struct drm_crtc_state *old_state)
{
        u32 val;

        WARN_ON(regmap_read_poll_timeout(engine->regs,
                                         SUN4I_BACKEND_REGBUFFCTL_REG,
                                         val, !(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL),
                                         100, 50000));
}

static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
                                      struct drm_crtc_state *crtc_state)
{
        struct drm_plane_state *plane_states[SUN4I_BACKEND_NUM_LAYERS] = { 0 };
        struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
        struct drm_atomic_state *state = crtc_state->state;
        struct drm_device *drm = state->dev;
        struct drm_plane *plane;
        unsigned int num_planes = 0;
        unsigned int num_alpha_planes = 0;
        unsigned int num_frontend_planes = 0;
        unsigned int num_alpha_planes_max = 1;
        unsigned int num_yuv_planes = 0;
        unsigned int current_pipe = 0;
        unsigned int i;

        DRM_DEBUG_DRIVER("Starting checking our planes\n");

        if (!crtc_state->planes_changed)
                return 0;

        drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) {
                struct drm_plane_state *plane_state =
                        drm_atomic_get_plane_state(state, plane);
                struct sun4i_layer_state *layer_state =
                        state_to_sun4i_layer_state(plane_state);
                struct drm_framebuffer *fb = plane_state->fb;

                if (!sun4i_backend_plane_is_supported(plane_state,
                                                      &layer_state->uses_frontend))
                        return -EINVAL;

                if (layer_state->uses_frontend) {
                        DRM_DEBUG_DRIVER("Using the frontend for plane %d\n",
                                         plane->index);
                        num_frontend_planes++;
                } else {
                        if (fb->format->is_yuv) {
                                DRM_DEBUG_DRIVER("Plane FB format is YUV\n");
                                num_yuv_planes++;
                        }
                }

                DRM_DEBUG_DRIVER("Plane FB format is %p4cc\n",
                                 &fb->format->format);
                if (fb->format->has_alpha || (plane_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
                        num_alpha_planes++;

                DRM_DEBUG_DRIVER("Plane zpos is %d\n",
                                 plane_state->normalized_zpos);

                /* Sort our planes by Zpos */
                plane_states[plane_state->normalized_zpos] = plane_state;

                num_planes++;
        }

        /* All our planes were disabled, bail out */
        if (!num_planes)
                return 0;

        /*
         * The hardware is a bit unusual here.
         *
         * Even though it supports 4 layers, it does the composition
         * in two separate steps.
         *
         * The first one is assigning a layer to one of its two
         * pipes. If more that 1 layer is assigned to the same pipe,
         * and if pixels overlaps, the pipe will take the pixel from
         * the layer with the highest priority.
         *
         * The second step is the actual alpha blending, that takes
         * the two pipes as input, and uses the potential alpha
         * component to do the transparency between the two.
         *
         * This two-step scenario makes us unable to guarantee a
         * robust alpha blending between the 4 layers in all
         * situations, since this means that we need to have one layer
         * with alpha at the lowest position of our two pipes.
         *
         * However, we cannot even do that on every platform, since
         * the hardware has a bug where the lowest plane of the lowest
         * pipe (pipe 0, priority 0), if it has any alpha, will
         * discard the pixel data entirely and just display the pixels
         * in the background color (black by default).
         *
         * This means that on the affected platforms, we effectively
         * have only three valid configurations with alpha, all of
         * them with the alpha being on pipe1 with the lowest
         * position, which can be 1, 2 or 3 depending on the number of
         * planes and their zpos.
         */

        /* For platforms that are not affected by the issue described above. */
        if (backend->quirks->supports_lowest_plane_alpha)
                num_alpha_planes_max++;

        if (num_alpha_planes > num_alpha_planes_max) {
                DRM_DEBUG_DRIVER("Too many planes with alpha, rejecting...\n");
                return -EINVAL;
        }

        /* We can't have an alpha plane at the lowest position */
        if (!backend->quirks->supports_lowest_plane_alpha &&
            (plane_states[0]->alpha != DRM_BLEND_ALPHA_OPAQUE))
                return -EINVAL;

        for (i = 1; i < num_planes; i++) {
                struct drm_plane_state *p_state = plane_states[i];
                struct drm_framebuffer *fb = p_state->fb;
                struct sun4i_layer_state *s_state = state_to_sun4i_layer_state(p_state);

                /*
                 * The only alpha position is the lowest plane of the
                 * second pipe.
                 */
                if (fb->format->has_alpha || (p_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
                        current_pipe++;

                s_state->pipe = current_pipe;
        }

        /* We can only have a single YUV plane at a time */
        if (num_yuv_planes > SUN4I_BACKEND_NUM_YUV_PLANES) {
                DRM_DEBUG_DRIVER("Too many planes with YUV, rejecting...\n");
                return -EINVAL;
        }

        if (num_frontend_planes > SUN4I_BACKEND_NUM_FRONTEND_LAYERS) {
                DRM_DEBUG_DRIVER("Too many planes going through the frontend, rejecting\n");
                return -EINVAL;
        }

        DRM_DEBUG_DRIVER("State valid with %u planes, %u alpha, %u video, %u YUV\n",
                         num_planes, num_alpha_planes, num_frontend_planes,
                         num_yuv_planes);

        return 0;
}

static void sun4i_backend_vblank_quirk(struct sunxi_engine *engine)
{
        struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
        struct sun4i_frontend *frontend = backend->frontend;

        if (!frontend)
                return;

        /*
         * In a teardown scenario with the frontend involved, we have
         * to keep the frontend enabled until the next vblank, and
         * only then disable it.
         *
         * This is due to the fact that the backend will not take into
         * account the new configuration (with the plane that used to
         * be fed by the frontend now disabled) until we write to the
         * commit bit and the hardware fetches the new configuration
         * during the next vblank.
         *
         * So we keep the frontend around in order to prevent any
         * visual artifacts.
         */
        spin_lock(&backend->frontend_lock);
        if (backend->frontend_teardown) {
                sun4i_frontend_exit(frontend);
                backend->frontend_teardown = false;
        }
        spin_unlock(&backend->frontend_lock);
};

static int sun4i_backend_init_sat(struct device *dev) {
        struct sun4i_backend *backend = dev_get_drvdata(dev);
        int ret;

        backend->sat_reset = devm_reset_control_get(dev, "sat");
        if (IS_ERR(backend->sat_reset)) {
                dev_err(dev, "Couldn't get the SAT reset line\n");
                return PTR_ERR(backend->sat_reset);
        }

        ret = reset_control_deassert(backend->sat_reset);
        if (ret) {
                dev_err(dev, "Couldn't deassert the SAT reset line\n");
                return ret;
        }

        backend->sat_clk = devm_clk_get(dev, "sat");
        if (IS_ERR(backend->sat_clk)) {
                dev_err(dev, "Couldn't get our SAT clock\n");
                ret = PTR_ERR(backend->sat_clk);
                goto err_assert_reset;
        }

        ret = clk_prepare_enable(backend->sat_clk);
        if (ret) {
                dev_err(dev, "Couldn't enable the SAT clock\n");
                return ret;
        }

        return 0;

err_assert_reset:
        reset_control_assert(backend->sat_reset);
        return ret;
}

static int sun4i_backend_free_sat(struct device *dev) {
        struct sun4i_backend *backend = dev_get_drvdata(dev);

        clk_disable_unprepare(backend->sat_clk);
        reset_control_assert(backend->sat_reset);

        return 0;
}

/*
 * The display backend can take video output from the display frontend, or
 * the display enhancement unit on the A80, as input for one it its layers.
 * This relationship within the display pipeline is encoded in the device
 * tree with of_graph, and we use it here to figure out which backend, if
 * there are 2 or more, we are currently probing. The number would be in
 * the "reg" property of the upstream output port endpoint.
 */
static int sun4i_backend_of_get_id(struct device_node *node)
{
        struct device_node *ep, *remote;
        struct of_endpoint of_ep;

        /* Input port is 0, and we want the first endpoint. */
        ep = of_graph_get_endpoint_by_regs(node, 0, -1);
        if (!ep)
                return -EINVAL;

        remote = of_graph_get_remote_endpoint(ep);
        of_node_put(ep);
        if (!remote)
                return -EINVAL;

        of_graph_parse_endpoint(remote, &of_ep);
        of_node_put(remote);
        return of_ep.id;
}

/* TODO: This needs to take multiple pipelines into account */
static struct sun4i_frontend *sun4i_backend_find_frontend(struct sun4i_drv *drv,
                                                          struct device_node *node)
{
        struct device_node *port, *ep, *remote;
        struct sun4i_frontend *frontend;

        port = of_graph_get_port_by_id(node, 0);
        if (!port)
                return ERR_PTR(-EINVAL);

        for_each_available_child_of_node(port, ep) {
                remote = of_graph_get_remote_port_parent(ep);
                if (!remote)
                        continue;
                of_node_put(remote);

                /* does this node match any registered engines? */
                list_for_each_entry(frontend, &drv->frontend_list, list) {
                        if (remote == frontend->node) {
                                of_node_put(port);
                                of_node_put(ep);
                                return frontend;
                        }
                }
        }
        of_node_put(port);
        return ERR_PTR(-EINVAL);
}

static const struct sunxi_engine_ops sun4i_backend_engine_ops = {
        .atomic_begin                   = sun4i_backend_atomic_begin,
        .atomic_check                   = sun4i_backend_atomic_check,
        .commit                         = sun4i_backend_commit,
        .layers_init                    = sun4i_layers_init,
        .apply_color_correction         = sun4i_backend_apply_color_correction,
        .disable_color_correction       = sun4i_backend_disable_color_correction,
        .vblank_quirk                   = sun4i_backend_vblank_quirk,
};

static const struct regmap_config sun4i_backend_regmap_config = {
        .reg_bits       = 32,
        .val_bits       = 32,
        .reg_stride     = 4,
        .max_register   = 0x5800,
};

static int sun4i_backend_bind(struct device *dev, struct device *master,
                              void *data)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct drm_device *drm = data;
        struct sun4i_drv *drv = drm->dev_private;
        struct sun4i_backend *backend;
        const struct sun4i_backend_quirks *quirks;
        struct resource *res;
        void __iomem *regs;
        int i, ret;

        backend = devm_kzalloc(dev, sizeof(*backend), GFP_KERNEL);
        if (!backend)
                return -ENOMEM;
        dev_set_drvdata(dev, backend);
        spin_lock_init(&backend->frontend_lock);

        if (of_find_property(dev->of_node, "interconnects", NULL)) {
                /*
                 * This assume we have the same DMA constraints for all our the
                 * devices in our pipeline (all the backends, but also the
                 * frontends). This sounds bad, but it has always been the case
                 * for us, and DRM doesn't do per-device allocation either, so
                 * we would need to fix DRM first...
                 */
                ret = of_dma_configure(drm->dev, dev->of_node, true);
                if (ret)
                        return ret;
        }

        backend->engine.node = dev->of_node;
        backend->engine.ops = &sun4i_backend_engine_ops;
        backend->engine.id = sun4i_backend_of_get_id(dev->of_node);
        if (backend->engine.id < 0)
                return backend->engine.id;

        backend->frontend = sun4i_backend_find_frontend(drv, dev->of_node);
        if (IS_ERR(backend->frontend))
                dev_warn(dev, "Couldn't find matching frontend, frontend features disabled\n");

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        regs = devm_ioremap_resource(dev, res);
        if (IS_ERR(regs))
                return PTR_ERR(regs);

        backend->reset = devm_reset_control_get(dev, NULL);
        if (IS_ERR(backend->reset)) {
                dev_err(dev, "Couldn't get our reset line\n");
                return PTR_ERR(backend->reset);
        }

        ret = reset_control_deassert(backend->reset);
        if (ret) {
                dev_err(dev, "Couldn't deassert our reset line\n");
                return ret;
        }

        backend->bus_clk = devm_clk_get(dev, "ahb");
        if (IS_ERR(backend->bus_clk)) {
                dev_err(dev, "Couldn't get the backend bus clock\n");
                ret = PTR_ERR(backend->bus_clk);
                goto err_assert_reset;
        }
        clk_prepare_enable(backend->bus_clk);

        backend->mod_clk = devm_clk_get(dev, "mod");
        if (IS_ERR(backend->mod_clk)) {
                dev_err(dev, "Couldn't get the backend module clock\n");
                ret = PTR_ERR(backend->mod_clk);
                goto err_disable_bus_clk;
        }

        ret = clk_set_rate_exclusive(backend->mod_clk, 300000000);
        if (ret) {
                dev_err(dev, "Couldn't set the module clock frequency\n");
                goto err_disable_bus_clk;
        }

        clk_prepare_enable(backend->mod_clk);

        backend->ram_clk = devm_clk_get(dev, "ram");
        if (IS_ERR(backend->ram_clk)) {
                dev_err(dev, "Couldn't get the backend RAM clock\n");
                ret = PTR_ERR(backend->ram_clk);
                goto err_disable_mod_clk;
        }
        clk_prepare_enable(backend->ram_clk);

        if (of_device_is_compatible(dev->of_node,
                                    "allwinner,sun8i-a33-display-backend")) {
                ret = sun4i_backend_init_sat(dev);
                if (ret) {
                        dev_err(dev, "Couldn't init SAT resources\n");
                        goto err_disable_ram_clk;
                }
        }

        backend->engine.regs = devm_regmap_init_mmio(dev, regs,
                                                     &sun4i_backend_regmap_config);
        if (IS_ERR(backend->engine.regs)) {
                dev_err(dev, "Couldn't create the backend regmap\n");
                return PTR_ERR(backend->engine.regs);
        }

        list_add_tail(&backend->engine.list, &drv->engine_list);

        /*
         * Many of the backend's layer configuration registers have
         * undefined default values. This poses a risk as we use
         * regmap_update_bits in some places, and don't overwrite
         * the whole register.
         *
         * Clear the registers here to have something predictable.
         */
        for (i = 0x800; i < 0x1000; i += 4)
                regmap_write(backend->engine.regs, i, 0);

        /* Disable registers autoloading */
        regmap_write(backend->engine.regs, SUN4I_BACKEND_REGBUFFCTL_REG,
                     SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS);

        /* Enable the backend */
        regmap_write(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
                     SUN4I_BACKEND_MODCTL_DEBE_EN |
                     SUN4I_BACKEND_MODCTL_START_CTL);

        /* Set output selection if needed */
        quirks = of_device_get_match_data(dev);
        if (quirks->needs_output_muxing) {
                /*
                 * We assume there is no dynamic muxing of backends
                 * and TCONs, so we select the backend with same ID.
                 *
                 * While dynamic selection might be interesting, since
                 * the CRTC is tied to the TCON, while the layers are
                 * tied to the backends, this means, we will need to
                 * switch between groups of layers. There might not be
                 * a way to represent this constraint in DRM.
                 */
                regmap_update_bits(backend->engine.regs,
                                   SUN4I_BACKEND_MODCTL_REG,
                                   SUN4I_BACKEND_MODCTL_OUT_SEL,
                                   (backend->engine.id
                                    ? SUN4I_BACKEND_MODCTL_OUT_LCD1
                                    : SUN4I_BACKEND_MODCTL_OUT_LCD0));
        }

        backend->quirks = quirks;

        return 0;

err_disable_ram_clk:
        clk_disable_unprepare(backend->ram_clk);
err_disable_mod_clk:
        clk_rate_exclusive_put(backend->mod_clk);
        clk_disable_unprepare(backend->mod_clk);
err_disable_bus_clk:
        clk_disable_unprepare(backend->bus_clk);
err_assert_reset:
        reset_control_assert(backend->reset);
        return ret;
}

static void sun4i_backend_unbind(struct device *dev, struct device *master,
                                 void *data)
{
        struct sun4i_backend *backend = dev_get_drvdata(dev);

        list_del(&backend->engine.list);

        if (of_device_is_compatible(dev->of_node,
                                    "allwinner,sun8i-a33-display-backend"))
                sun4i_backend_free_sat(dev);

        clk_disable_unprepare(backend->ram_clk);
        clk_rate_exclusive_put(backend->mod_clk);
        clk_disable_unprepare(backend->mod_clk);
        clk_disable_unprepare(backend->bus_clk);
        reset_control_assert(backend->reset);
}

static const struct component_ops sun4i_backend_ops = {
        .bind   = sun4i_backend_bind,
        .unbind = sun4i_backend_unbind,
};

static int sun4i_backend_probe(struct platform_device *pdev)
{
        return component_add(&pdev->dev, &sun4i_backend_ops);
}

static int sun4i_backend_remove(struct platform_device *pdev)
{
        component_del(&pdev->dev, &sun4i_backend_ops);

        return 0;
}

static const struct sun4i_backend_quirks sun4i_backend_quirks = {
        .needs_output_muxing = true,
};

static const struct sun4i_backend_quirks sun5i_backend_quirks = {
};

static const struct sun4i_backend_quirks sun6i_backend_quirks = {
};

static const struct sun4i_backend_quirks sun7i_backend_quirks = {
        .needs_output_muxing = true,
};

static const struct sun4i_backend_quirks sun8i_a33_backend_quirks = {
        .supports_lowest_plane_alpha = true,
};

static const struct sun4i_backend_quirks sun9i_backend_quirks = {
};

static const struct of_device_id sun4i_backend_of_table[] = {
        {
                .compatible = "allwinner,sun4i-a10-display-backend",
                .data = &sun4i_backend_quirks,

        },
        {
                .compatible = "allwinner,sun5i-a13-display-backend",
                .data = &sun5i_backend_quirks,
        },
        {
                .compatible = "allwinner,sun6i-a31-display-backend",
                .data = &sun6i_backend_quirks,
        },
        {
                .compatible = "allwinner,sun7i-a20-display-backend",
                .data = &sun7i_backend_quirks,
        },
        {
                .compatible = "allwinner,sun8i-a23-display-backend",
                .data = &sun8i_a33_backend_quirks,
        },
        {
                .compatible = "allwinner,sun8i-a33-display-backend",
                .data = &sun8i_a33_backend_quirks,
        },
        {
                .compatible = "allwinner,sun9i-a80-display-backend",
                .data = &sun9i_backend_quirks,
        },
        { }
};
MODULE_DEVICE_TABLE(of, sun4i_backend_of_table);

static struct platform_driver sun4i_backend_platform_driver = {
        .probe          = sun4i_backend_probe,
        .remove         = sun4i_backend_remove,
        .driver         = {
                .name           = "sun4i-backend",
                .of_match_table = sun4i_backend_of_table,
        },
};
module_platform_driver(sun4i_backend_platform_driver);

MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
MODULE_DESCRIPTION("Allwinner A10 Display Backend Driver");
MODULE_LICENSE("GPL");