Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1039 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
new file mode 100644
index 000000000..335fd0edb
--- /dev/null
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -0,0 +1,1039 @@
+// 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_blend.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_fb_dma_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_dma_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);
+
+	/* 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;
+	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);
+
+	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 dma_addr;
+
+	/* 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 */
+	dma_addr = drm_fb_dma_get_gem_addr(fb, state, 0);
+	DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &dma_addr);
+
+	if (fb->format->is_yuv)
+		return sun4i_backend_update_yuv_buffer(backend, fb, dma_addr);
+
+	/* Write the 32 lower bits of the address (in bits) */
+	lo_paddr = dma_addr << 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 = dma_addr >> 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 void sun4i_backend_mode_set(struct sunxi_engine *engine,
+				   const struct drm_display_mode *mode)
+{
+	bool interlaced = !!(mode->flags & DRM_MODE_FLAG_INTERLACE);
+
+	DRM_DEBUG_DRIVER("Updating global size W: %u H: %u\n",
+			 mode->hdisplay, mode->vdisplay);
+
+	regmap_write(engine->regs, SUN4I_BACKEND_DISSIZE_REG,
+		     SUN4I_BACKEND_DISSIZE(mode->hdisplay, mode->vdisplay));
+
+	regmap_update_bits(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");
+}
+
+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,
+	.mode_set			= sun4i_backend_mode_set,
+};
+
+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;
+	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_property_present(dev->of_node, "interconnects")) {
+		/*
+		 * 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");
+
+	regs = devm_platform_ioremap_resource(pdev, 0);
+	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 void sun4i_backend_remove(struct platform_device *pdev)
+{
+	component_del(&pdev->dev, &sun4i_backend_ops);
+}
+
+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_new	= 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");