drivers/gpu/drm/sun4i/sun4i_backend.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2015 Free Electrons
  * Copyright (C) 2015 NextThing Co
  *
  * Maxime Ripard <maxime.ripard@free-electrons.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of
  * the License, or (at your option) any later version.
  */

 #include <drm/drmP.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_plane_helper.h>

 #include <linux/component.h>
 #include <linux/reset.h>

 #include "sun4i_backend.h"
 #include "sun4i_drv.h"

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

 void sun4i_backend_apply_color_correction(struct sun4i_backend *backend)
 {
 	int i;

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

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

 	for (i = 0; i < 12; i++)
 		regmap_write(backend->regs, SUN4I_BACKEND_OCRCOEF_REG(i),
 			     sunxi_rgb2yuv_coef[i]);
 }
 EXPORT_SYMBOL(sun4i_backend_apply_color_correction);

 void sun4i_backend_disable_color_correction(struct sun4i_backend *backend)
 {
 	DRM_DEBUG_DRIVER("Disabling color correction\n");

 	/* Disable color correction */
 	regmap_update_bits(backend->regs, SUN4I_BACKEND_OCCTL_REG,
 			   SUN4I_BACKEND_OCCTL_ENABLE, 0);
 }
 EXPORT_SYMBOL(sun4i_backend_disable_color_correction);

 void sun4i_backend_commit(struct sun4i_backend *backend)
 {
 	DRM_DEBUG_DRIVER("Committing changes\n");

 	regmap_write(backend->regs, SUN4I_BACKEND_REGBUFFCTL_REG,
 		     SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS |
 		     SUN4I_BACKEND_REGBUFFCTL_LOADCTL);
 }
 EXPORT_SYMBOL(sun4i_backend_commit);

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

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

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

 	regmap_update_bits(backend->regs, SUN4I_BACKEND_MODCTL_REG,
 			   SUN4I_BACKEND_MODCTL_LAY_EN(layer), val);
 }
 EXPORT_SYMBOL(sun4i_backend_layer_enable);

 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_XRGB8888:
 		*mode = SUN4I_BACKEND_LAY_FBFMT_XRGB8888;
 		break;

 	case DRM_FORMAT_RGB888:
 		*mode = SUN4I_BACKEND_LAY_FBFMT_RGB888;
 		break;

 	default:
 		return -EINVAL;
 	}

 	return 0;
 }

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

 	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->regs, SUN4I_BACKEND_DISSIZE_REG,
 			     SUN4I_BACKEND_DISSIZE(state->crtc_w,
 						   state->crtc_h));
 	}

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

 	/* Set height and width */
 	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n",
 			 state->crtc_w, state->crtc_h);
 	regmap_write(backend->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->regs, SUN4I_BACKEND_LAYCOOR_REG(layer),
 		     SUN4I_BACKEND_LAYCOOR(state->crtc_x,
 					   state->crtc_y));

 	return 0;
 }
 EXPORT_SYMBOL(sun4i_backend_update_layer_coord);

 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;

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

 	regmap_update_bits(backend->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");

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

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

 	return 0;
 }
 EXPORT_SYMBOL(sun4i_backend_update_layer_formats);

 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;
 	struct drm_gem_cma_object *gem;
 	u32 lo_paddr, hi_paddr;
 	dma_addr_t paddr;
 	int bpp;

 	/* Get the physical address of the buffer in memory */
 	gem = drm_fb_cma_get_gem_obj(fb, 0);

 	DRM_DEBUG_DRIVER("Using GEM @ 0x%x\n", gem->paddr);

 	/* Compute the start of the displayed memory */
 	bpp = drm_format_plane_cpp(fb->pixel_format, 0);
 	paddr = gem->paddr + fb->offsets[0];
 	paddr += (state->src_x >> 16) * bpp;
 	paddr += (state->src_y >> 16) * fb->pitches[0];

 	DRM_DEBUG_DRIVER("Setting buffer address to 0x%x\n", 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->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->regs, SUN4I_BACKEND_LAYFB_H4ADD_REG,
 			   SUN4I_BACKEND_LAYFB_H4ADD_MSK(layer),
 			   SUN4I_BACKEND_LAYFB_H4ADD(layer, hi_paddr));

 	return 0;
 }
 EXPORT_SYMBOL(sun4i_backend_update_layer_buffer);

 static 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;
 	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);
 	drv->backend = backend;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	regs = devm_ioremap_resource(dev, res);
 	if (IS_ERR(regs)) {
 		dev_err(dev, "Couldn't map the backend registers\n");
 		return PTR_ERR(regs);
 	}

 	backend->regs = devm_regmap_init_mmio(dev, regs,
 					      &sun4i_backend_regmap_config);
 	if (IS_ERR(backend->regs)) {
 		dev_err(dev, "Couldn't create the backend0 regmap\n");
 		return PTR_ERR(backend->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;
 	}
 	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);

 	/* Reset the registers */
 	for (i = 0x800; i < 0x1000; i += 4)
 		regmap_write(backend->regs, i, 0);

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

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

 	return 0;

 err_disable_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);

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

 static 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 of_device_id sun4i_backend_of_table[] = {
 	{ .compatible = "allwinner,sun5i-a13-display-backend" },
 	{ }
 };
 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");
	/*
	* Copyright (C) 2015 Free Electrons
	* Copyright (C) 2015 NextThing Co
	*
	* Maxime Ripard <maxime.ripard@free-electrons.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation; either version 2 of
	* the License, or (at your option) any later version.
	*/

	#include <drm/drmP.h>
	#include <drm/drm_atomic_helper.h>
	#include <drm/drm_crtc.h>
	#include <drm/drm_crtc_helper.h>
	#include <drm/drm_fb_cma_helper.h>
	#include <drm/drm_gem_cma_helper.h>
	#include <drm/drm_plane_helper.h>

	#include <linux/component.h>
	#include <linux/reset.h>

	#include "sun4i_backend.h"
	#include "sun4i_drv.h"

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

	void sun4i_backend_apply_color_correction(struct sun4i_backend *backend)
	{
	int i;

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

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

	for (i = 0; i < 12; i++)
	regmap_write(backend->regs, SUN4I_BACKEND_OCRCOEF_REG(i),
	sunxi_rgb2yuv_coef[i]);
	}
	EXPORT_SYMBOL(sun4i_backend_apply_color_correction);

	void sun4i_backend_disable_color_correction(struct sun4i_backend *backend)
	{
	DRM_DEBUG_DRIVER("Disabling color correction\n");

	/* Disable color correction */
	regmap_update_bits(backend->regs, SUN4I_BACKEND_OCCTL_REG,
	SUN4I_BACKEND_OCCTL_ENABLE, 0);
	}
	EXPORT_SYMBOL(sun4i_backend_disable_color_correction);

	void sun4i_backend_commit(struct sun4i_backend *backend)
	{
	DRM_DEBUG_DRIVER("Committing changes\n");

	regmap_write(backend->regs, SUN4I_BACKEND_REGBUFFCTL_REG,
	SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS \|
	SUN4I_BACKEND_REGBUFFCTL_LOADCTL);
	}
	EXPORT_SYMBOL(sun4i_backend_commit);

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

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

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

	regmap_update_bits(backend->regs, SUN4I_BACKEND_MODCTL_REG,
	SUN4I_BACKEND_MODCTL_LAY_EN(layer), val);
	}
	EXPORT_SYMBOL(sun4i_backend_layer_enable);

	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_XRGB8888:
	*mode = SUN4I_BACKEND_LAY_FBFMT_XRGB8888;
	break;

	case DRM_FORMAT_RGB888:
	*mode = SUN4I_BACKEND_LAY_FBFMT_RGB888;
	break;

	default:
	return -EINVAL;
	}

	return 0;
	}

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

	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->regs, SUN4I_BACKEND_DISSIZE_REG,
	SUN4I_BACKEND_DISSIZE(state->crtc_w,
	state->crtc_h));
	}

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

	/* Set height and width */
	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n",
	state->crtc_w, state->crtc_h);
	regmap_write(backend->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->regs, SUN4I_BACKEND_LAYCOOR_REG(layer),
	SUN4I_BACKEND_LAYCOOR(state->crtc_x,
	state->crtc_y));

	return 0;
	}
	EXPORT_SYMBOL(sun4i_backend_update_layer_coord);

	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;

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

	regmap_update_bits(backend->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");

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

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

	return 0;
	}
	EXPORT_SYMBOL(sun4i_backend_update_layer_formats);

	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;
	struct drm_gem_cma_object *gem;
	u32 lo_paddr, hi_paddr;
	dma_addr_t paddr;
	int bpp;

	/* Get the physical address of the buffer in memory */
	gem = drm_fb_cma_get_gem_obj(fb, 0);

	DRM_DEBUG_DRIVER("Using GEM @ 0x%x\n", gem->paddr);

	/* Compute the start of the displayed memory */
	bpp = drm_format_plane_cpp(fb->pixel_format, 0);
	paddr = gem->paddr + fb->offsets[0];
	paddr += (state->src_x >> 16) * bpp;
	paddr += (state->src_y >> 16) * fb->pitches[0];

	DRM_DEBUG_DRIVER("Setting buffer address to 0x%x\n", 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->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->regs, SUN4I_BACKEND_LAYFB_H4ADD_REG,
	SUN4I_BACKEND_LAYFB_H4ADD_MSK(layer),
	SUN4I_BACKEND_LAYFB_H4ADD(layer, hi_paddr));

	return 0;
	}
	EXPORT_SYMBOL(sun4i_backend_update_layer_buffer);

	static 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;
	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);
	drv->backend = backend;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	regs = devm_ioremap_resource(dev, res);
	if (IS_ERR(regs)) {
	dev_err(dev, "Couldn't map the backend registers\n");
	return PTR_ERR(regs);
	}

	backend->regs = devm_regmap_init_mmio(dev, regs,
	&sun4i_backend_regmap_config);
	if (IS_ERR(backend->regs)) {
	dev_err(dev, "Couldn't create the backend0 regmap\n");
	return PTR_ERR(backend->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;
	}
	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);

	/* Reset the registers */
	for (i = 0x800; i < 0x1000; i += 4)
	regmap_write(backend->regs, i, 0);

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

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

	return 0;

	err_disable_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);

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

	static 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 of_device_id sun4i_backend_of_table[] = {
	{ .compatible = "allwinner,sun5i-a13-display-backend" },
	{ }
	};
	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");