Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 1376 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
new file mode 100644
index 000000000..a6ac56580
--- /dev/null
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -0,0 +1,1376 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MIPI Display Bus Interface (DBI) LCD controller support
+ *
+ * Copyright 2016 Noralf Trønnes
+ */
+
+#include <linux/backlight.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#include <drm/drm_connector.h>
+#include <drm/drm_damage_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_file.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_mipi_dbi.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_rect.h>
+#include <video/mipi_display.h>
+
+#define MIPI_DBI_MAX_SPI_READ_SPEED 2000000 /* 2MHz */
+
+#define DCS_POWER_MODE_DISPLAY			BIT(2)
+#define DCS_POWER_MODE_DISPLAY_NORMAL_MODE	BIT(3)
+#define DCS_POWER_MODE_SLEEP_MODE		BIT(4)
+#define DCS_POWER_MODE_PARTIAL_MODE		BIT(5)
+#define DCS_POWER_MODE_IDLE_MODE		BIT(6)
+#define DCS_POWER_MODE_RESERVED_MASK		(BIT(0) | BIT(1) | BIT(7))
+
+/**
+ * DOC: overview
+ *
+ * This library provides helpers for MIPI Display Bus Interface (DBI)
+ * compatible display controllers.
+ *
+ * Many controllers for tiny lcd displays are MIPI compliant and can use this
+ * library. If a controller uses registers 0x2A and 0x2B to set the area to
+ * update and uses register 0x2C to write to frame memory, it is most likely
+ * MIPI compliant.
+ *
+ * Only MIPI Type 1 displays are supported since a full frame memory is needed.
+ *
+ * There are 3 MIPI DBI implementation types:
+ *
+ * A. Motorola 6800 type parallel bus
+ *
+ * B. Intel 8080 type parallel bus
+ *
+ * C. SPI type with 3 options:
+ *
+ *    1. 9-bit with the Data/Command signal as the ninth bit
+ *    2. Same as above except it's sent as 16 bits
+ *    3. 8-bit with the Data/Command signal as a separate D/CX pin
+ *
+ * Currently mipi_dbi only supports Type C options 1 and 3 with
+ * mipi_dbi_spi_init().
+ */
+
+#define MIPI_DBI_DEBUG_COMMAND(cmd, data, len) \
+({ \
+	if (!len) \
+		DRM_DEBUG_DRIVER("cmd=%02x\n", cmd); \
+	else if (len <= 32) \
+		DRM_DEBUG_DRIVER("cmd=%02x, par=%*ph\n", cmd, (int)len, data);\
+	else \
+		DRM_DEBUG_DRIVER("cmd=%02x, len=%zu\n", cmd, len); \
+})
+
+static const u8 mipi_dbi_dcs_read_commands[] = {
+	MIPI_DCS_GET_DISPLAY_ID,
+	MIPI_DCS_GET_RED_CHANNEL,
+	MIPI_DCS_GET_GREEN_CHANNEL,
+	MIPI_DCS_GET_BLUE_CHANNEL,
+	MIPI_DCS_GET_DISPLAY_STATUS,
+	MIPI_DCS_GET_POWER_MODE,
+	MIPI_DCS_GET_ADDRESS_MODE,
+	MIPI_DCS_GET_PIXEL_FORMAT,
+	MIPI_DCS_GET_DISPLAY_MODE,
+	MIPI_DCS_GET_SIGNAL_MODE,
+	MIPI_DCS_GET_DIAGNOSTIC_RESULT,
+	MIPI_DCS_READ_MEMORY_START,
+	MIPI_DCS_READ_MEMORY_CONTINUE,
+	MIPI_DCS_GET_SCANLINE,
+	MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
+	MIPI_DCS_GET_CONTROL_DISPLAY,
+	MIPI_DCS_GET_POWER_SAVE,
+	MIPI_DCS_GET_CABC_MIN_BRIGHTNESS,
+	MIPI_DCS_READ_DDB_START,
+	MIPI_DCS_READ_DDB_CONTINUE,
+	0, /* sentinel */
+};
+
+static bool mipi_dbi_command_is_read(struct mipi_dbi *dbi, u8 cmd)
+{
+	unsigned int i;
+
+	if (!dbi->read_commands)
+		return false;
+
+	for (i = 0; i < 0xff; i++) {
+		if (!dbi->read_commands[i])
+			return false;
+		if (cmd == dbi->read_commands[i])
+			return true;
+	}
+
+	return false;
+}
+
+/**
+ * mipi_dbi_command_read - MIPI DCS read command
+ * @dbi: MIPI DBI structure
+ * @cmd: Command
+ * @val: Value read
+ *
+ * Send MIPI DCS read command to the controller.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_command_read(struct mipi_dbi *dbi, u8 cmd, u8 *val)
+{
+	if (!dbi->read_commands)
+		return -EACCES;
+
+	if (!mipi_dbi_command_is_read(dbi, cmd))
+		return -EINVAL;
+
+	return mipi_dbi_command_buf(dbi, cmd, val, 1);
+}
+EXPORT_SYMBOL(mipi_dbi_command_read);
+
+/**
+ * mipi_dbi_command_buf - MIPI DCS command with parameter(s) in an array
+ * @dbi: MIPI DBI structure
+ * @cmd: Command
+ * @data: Parameter buffer
+ * @len: Buffer length
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_command_buf(struct mipi_dbi *dbi, u8 cmd, u8 *data, size_t len)
+{
+	u8 *cmdbuf;
+	int ret;
+
+	/* SPI requires dma-safe buffers */
+	cmdbuf = kmemdup(&cmd, 1, GFP_KERNEL);
+	if (!cmdbuf)
+		return -ENOMEM;
+
+	mutex_lock(&dbi->cmdlock);
+	ret = dbi->command(dbi, cmdbuf, data, len);
+	mutex_unlock(&dbi->cmdlock);
+
+	kfree(cmdbuf);
+
+	return ret;
+}
+EXPORT_SYMBOL(mipi_dbi_command_buf);
+
+/* This should only be used by mipi_dbi_command() */
+int mipi_dbi_command_stackbuf(struct mipi_dbi *dbi, u8 cmd, const u8 *data,
+			      size_t len)
+{
+	u8 *buf;
+	int ret;
+
+	buf = kmemdup(data, len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = mipi_dbi_command_buf(dbi, cmd, buf, len);
+
+	kfree(buf);
+
+	return ret;
+}
+EXPORT_SYMBOL(mipi_dbi_command_stackbuf);
+
+/**
+ * mipi_dbi_buf_copy - Copy a framebuffer, transforming it if necessary
+ * @dst: The destination buffer
+ * @fb: The source framebuffer
+ * @clip: Clipping rectangle of the area to be copied
+ * @swap: When true, swap MSB/LSB of 16-bit values
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
+		      struct drm_rect *clip, bool swap)
+{
+	struct drm_gem_object *gem = drm_gem_fb_get_obj(fb, 0);
+	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
+	struct iosys_map data[DRM_FORMAT_MAX_PLANES];
+	struct iosys_map dst_map = IOSYS_MAP_INIT_VADDR(dst);
+	int ret;
+
+	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
+	if (ret)
+		return ret;
+
+	ret = drm_gem_fb_vmap(fb, map, data);
+	if (ret)
+		goto out_drm_gem_fb_end_cpu_access;
+
+	switch (fb->format->format) {
+	case DRM_FORMAT_RGB565:
+		if (swap)
+			drm_fb_swab(&dst_map, NULL, data, fb, clip, !gem->import_attach);
+		else
+			drm_fb_memcpy(&dst_map, NULL, data, fb, clip);
+		break;
+	case DRM_FORMAT_XRGB8888:
+		drm_fb_xrgb8888_to_rgb565(&dst_map, NULL, data, fb, clip, swap);
+		break;
+	default:
+		drm_err_once(fb->dev, "Format is not supported: %p4cc\n",
+			     &fb->format->format);
+		ret = -EINVAL;
+	}
+
+	drm_gem_fb_vunmap(fb, map);
+out_drm_gem_fb_end_cpu_access:
+	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
+
+	return ret;
+}
+EXPORT_SYMBOL(mipi_dbi_buf_copy);
+
+static void mipi_dbi_set_window_address(struct mipi_dbi_dev *dbidev,
+					unsigned int xs, unsigned int xe,
+					unsigned int ys, unsigned int ye)
+{
+	struct mipi_dbi *dbi = &dbidev->dbi;
+
+	xs += dbidev->left_offset;
+	xe += dbidev->left_offset;
+	ys += dbidev->top_offset;
+	ye += dbidev->top_offset;
+
+	mipi_dbi_command(dbi, MIPI_DCS_SET_COLUMN_ADDRESS, (xs >> 8) & 0xff,
+			 xs & 0xff, (xe >> 8) & 0xff, xe & 0xff);
+	mipi_dbi_command(dbi, MIPI_DCS_SET_PAGE_ADDRESS, (ys >> 8) & 0xff,
+			 ys & 0xff, (ye >> 8) & 0xff, ye & 0xff);
+}
+
+static void mipi_dbi_fb_dirty(struct drm_framebuffer *fb, struct drm_rect *rect)
+{
+	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
+	struct iosys_map data[DRM_FORMAT_MAX_PLANES];
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(fb->dev);
+	unsigned int height = rect->y2 - rect->y1;
+	unsigned int width = rect->x2 - rect->x1;
+	struct mipi_dbi *dbi = &dbidev->dbi;
+	bool swap = dbi->swap_bytes;
+	int idx, ret = 0;
+	bool full;
+	void *tr;
+
+	if (WARN_ON(!fb))
+		return;
+
+	if (!drm_dev_enter(fb->dev, &idx))
+		return;
+
+	ret = drm_gem_fb_vmap(fb, map, data);
+	if (ret)
+		goto err_drm_dev_exit;
+
+	full = width == fb->width && height == fb->height;
+
+	DRM_DEBUG_KMS("Flushing [FB:%d] " DRM_RECT_FMT "\n", fb->base.id, DRM_RECT_ARG(rect));
+
+	if (!dbi->dc || !full || swap ||
+	    fb->format->format == DRM_FORMAT_XRGB8888) {
+		tr = dbidev->tx_buf;
+		ret = mipi_dbi_buf_copy(dbidev->tx_buf, fb, rect, swap);
+		if (ret)
+			goto err_msg;
+	} else {
+		tr = data[0].vaddr; /* TODO: Use mapping abstraction properly */
+	}
+
+	mipi_dbi_set_window_address(dbidev, rect->x1, rect->x2 - 1, rect->y1,
+				    rect->y2 - 1);
+
+	ret = mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START, tr,
+				   width * height * 2);
+err_msg:
+	if (ret)
+		drm_err_once(fb->dev, "Failed to update display %d\n", ret);
+
+	drm_gem_fb_vunmap(fb, map);
+
+err_drm_dev_exit:
+	drm_dev_exit(idx);
+}
+
+/**
+ * mipi_dbi_pipe_mode_valid - MIPI DBI mode-valid helper
+ * @pipe: Simple display pipe
+ * @mode: The mode to test
+ *
+ * This function validates a given display mode against the MIPI DBI's hardware
+ * display. Drivers can use this as their &drm_simple_display_pipe_funcs->mode_valid
+ * callback.
+ */
+enum drm_mode_status mipi_dbi_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
+					      const struct drm_display_mode *mode)
+{
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(pipe->crtc.dev);
+
+	return drm_crtc_helper_mode_valid_fixed(&pipe->crtc, mode, &dbidev->mode);
+}
+EXPORT_SYMBOL(mipi_dbi_pipe_mode_valid);
+
+/**
+ * mipi_dbi_pipe_update - Display pipe update helper
+ * @pipe: Simple display pipe
+ * @old_state: Old plane state
+ *
+ * This function handles framebuffer flushing and vblank events. Drivers can use
+ * this as their &drm_simple_display_pipe_funcs->update callback.
+ */
+void mipi_dbi_pipe_update(struct drm_simple_display_pipe *pipe,
+			  struct drm_plane_state *old_state)
+{
+	struct drm_plane_state *state = pipe->plane.state;
+	struct drm_rect rect;
+
+	if (!pipe->crtc.state->active)
+		return;
+
+	if (drm_atomic_helper_damage_merged(old_state, state, &rect))
+		mipi_dbi_fb_dirty(state->fb, &rect);
+}
+EXPORT_SYMBOL(mipi_dbi_pipe_update);
+
+/**
+ * mipi_dbi_enable_flush - MIPI DBI enable helper
+ * @dbidev: MIPI DBI device structure
+ * @crtc_state: CRTC state
+ * @plane_state: Plane state
+ *
+ * Flushes the whole framebuffer and enables the backlight. Drivers can use this
+ * in their &drm_simple_display_pipe_funcs->enable callback.
+ *
+ * Note: Drivers which don't use mipi_dbi_pipe_update() because they have custom
+ * framebuffer flushing, can't use this function since they both use the same
+ * flushing code.
+ */
+void mipi_dbi_enable_flush(struct mipi_dbi_dev *dbidev,
+			   struct drm_crtc_state *crtc_state,
+			   struct drm_plane_state *plane_state)
+{
+	struct drm_framebuffer *fb = plane_state->fb;
+	struct drm_rect rect = {
+		.x1 = 0,
+		.x2 = fb->width,
+		.y1 = 0,
+		.y2 = fb->height,
+	};
+	int idx;
+
+	if (!drm_dev_enter(&dbidev->drm, &idx))
+		return;
+
+	mipi_dbi_fb_dirty(fb, &rect);
+	backlight_enable(dbidev->backlight);
+
+	drm_dev_exit(idx);
+}
+EXPORT_SYMBOL(mipi_dbi_enable_flush);
+
+static void mipi_dbi_blank(struct mipi_dbi_dev *dbidev)
+{
+	struct drm_device *drm = &dbidev->drm;
+	u16 height = drm->mode_config.min_height;
+	u16 width = drm->mode_config.min_width;
+	struct mipi_dbi *dbi = &dbidev->dbi;
+	size_t len = width * height * 2;
+	int idx;
+
+	if (!drm_dev_enter(drm, &idx))
+		return;
+
+	memset(dbidev->tx_buf, 0, len);
+
+	mipi_dbi_set_window_address(dbidev, 0, width - 1, 0, height - 1);
+	mipi_dbi_command_buf(dbi, MIPI_DCS_WRITE_MEMORY_START,
+			     (u8 *)dbidev->tx_buf, len);
+
+	drm_dev_exit(idx);
+}
+
+/**
+ * mipi_dbi_pipe_disable - MIPI DBI pipe disable helper
+ * @pipe: Display pipe
+ *
+ * This function disables backlight if present, if not the display memory is
+ * blanked. The regulator is disabled if in use. Drivers can use this as their
+ * &drm_simple_display_pipe_funcs->disable callback.
+ */
+void mipi_dbi_pipe_disable(struct drm_simple_display_pipe *pipe)
+{
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(pipe->crtc.dev);
+
+	DRM_DEBUG_KMS("\n");
+
+	if (dbidev->backlight)
+		backlight_disable(dbidev->backlight);
+	else
+		mipi_dbi_blank(dbidev);
+
+	if (dbidev->regulator)
+		regulator_disable(dbidev->regulator);
+}
+EXPORT_SYMBOL(mipi_dbi_pipe_disable);
+
+static int mipi_dbi_connector_get_modes(struct drm_connector *connector)
+{
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(connector->dev);
+
+	return drm_connector_helper_get_modes_fixed(connector, &dbidev->mode);
+}
+
+static const struct drm_connector_helper_funcs mipi_dbi_connector_hfuncs = {
+	.get_modes = mipi_dbi_connector_get_modes,
+};
+
+static const struct drm_connector_funcs mipi_dbi_connector_funcs = {
+	.reset = drm_atomic_helper_connector_reset,
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static int mipi_dbi_rotate_mode(struct drm_display_mode *mode,
+				unsigned int rotation)
+{
+	if (rotation == 0 || rotation == 180) {
+		return 0;
+	} else if (rotation == 90 || rotation == 270) {
+		swap(mode->hdisplay, mode->vdisplay);
+		swap(mode->hsync_start, mode->vsync_start);
+		swap(mode->hsync_end, mode->vsync_end);
+		swap(mode->htotal, mode->vtotal);
+		swap(mode->width_mm, mode->height_mm);
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+
+static const struct drm_mode_config_funcs mipi_dbi_mode_config_funcs = {
+	.fb_create = drm_gem_fb_create_with_dirty,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+static const uint32_t mipi_dbi_formats[] = {
+	DRM_FORMAT_RGB565,
+	DRM_FORMAT_XRGB8888,
+};
+
+/**
+ * mipi_dbi_dev_init_with_formats - MIPI DBI device initialization with custom formats
+ * @dbidev: MIPI DBI device structure to initialize
+ * @funcs: Display pipe functions
+ * @formats: Array of supported formats (DRM_FORMAT\_\*).
+ * @format_count: Number of elements in @formats
+ * @mode: Display mode
+ * @rotation: Initial rotation in degrees Counter Clock Wise
+ * @tx_buf_size: Allocate a transmit buffer of this size.
+ *
+ * This function sets up a &drm_simple_display_pipe with a &drm_connector that
+ * has one fixed &drm_display_mode which is rotated according to @rotation.
+ * This mode is used to set the mode config min/max width/height properties.
+ *
+ * Use mipi_dbi_dev_init() if you don't need custom formats.
+ *
+ * Note:
+ * Some of the helper functions expects RGB565 to be the default format and the
+ * transmit buffer sized to fit that.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_dev_init_with_formats(struct mipi_dbi_dev *dbidev,
+				   const struct drm_simple_display_pipe_funcs *funcs,
+				   const uint32_t *formats, unsigned int format_count,
+				   const struct drm_display_mode *mode,
+				   unsigned int rotation, size_t tx_buf_size)
+{
+	static const uint64_t modifiers[] = {
+		DRM_FORMAT_MOD_LINEAR,
+		DRM_FORMAT_MOD_INVALID
+	};
+	struct drm_device *drm = &dbidev->drm;
+	int ret;
+
+	if (!dbidev->dbi.command)
+		return -EINVAL;
+
+	ret = drmm_mode_config_init(drm);
+	if (ret)
+		return ret;
+
+	dbidev->tx_buf = devm_kmalloc(drm->dev, tx_buf_size, GFP_KERNEL);
+	if (!dbidev->tx_buf)
+		return -ENOMEM;
+
+	drm_mode_copy(&dbidev->mode, mode);
+	ret = mipi_dbi_rotate_mode(&dbidev->mode, rotation);
+	if (ret) {
+		DRM_ERROR("Illegal rotation value %u\n", rotation);
+		return -EINVAL;
+	}
+
+	drm_connector_helper_add(&dbidev->connector, &mipi_dbi_connector_hfuncs);
+	ret = drm_connector_init(drm, &dbidev->connector, &mipi_dbi_connector_funcs,
+				 DRM_MODE_CONNECTOR_SPI);
+	if (ret)
+		return ret;
+
+	ret = drm_simple_display_pipe_init(drm, &dbidev->pipe, funcs, formats, format_count,
+					   modifiers, &dbidev->connector);
+	if (ret)
+		return ret;
+
+	drm_plane_enable_fb_damage_clips(&dbidev->pipe.plane);
+
+	drm->mode_config.funcs = &mipi_dbi_mode_config_funcs;
+	drm->mode_config.min_width = dbidev->mode.hdisplay;
+	drm->mode_config.max_width = dbidev->mode.hdisplay;
+	drm->mode_config.min_height = dbidev->mode.vdisplay;
+	drm->mode_config.max_height = dbidev->mode.vdisplay;
+	dbidev->rotation = rotation;
+
+	DRM_DEBUG_KMS("rotation = %u\n", rotation);
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dbi_dev_init_with_formats);
+
+/**
+ * mipi_dbi_dev_init - MIPI DBI device initialization
+ * @dbidev: MIPI DBI device structure to initialize
+ * @funcs: Display pipe functions
+ * @mode: Display mode
+ * @rotation: Initial rotation in degrees Counter Clock Wise
+ *
+ * This function sets up a &drm_simple_display_pipe with a &drm_connector that
+ * has one fixed &drm_display_mode which is rotated according to @rotation.
+ * This mode is used to set the mode config min/max width/height properties.
+ * Additionally &mipi_dbi.tx_buf is allocated.
+ *
+ * Supported formats: Native RGB565 and emulated XRGB8888.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_dev_init(struct mipi_dbi_dev *dbidev,
+		      const struct drm_simple_display_pipe_funcs *funcs,
+		      const struct drm_display_mode *mode, unsigned int rotation)
+{
+	size_t bufsize = mode->vdisplay * mode->hdisplay * sizeof(u16);
+
+	dbidev->drm.mode_config.preferred_depth = 16;
+
+	return mipi_dbi_dev_init_with_formats(dbidev, funcs, mipi_dbi_formats,
+					      ARRAY_SIZE(mipi_dbi_formats), mode,
+					      rotation, bufsize);
+}
+EXPORT_SYMBOL(mipi_dbi_dev_init);
+
+/**
+ * mipi_dbi_hw_reset - Hardware reset of controller
+ * @dbi: MIPI DBI structure
+ *
+ * Reset controller if the &mipi_dbi->reset gpio is set.
+ */
+void mipi_dbi_hw_reset(struct mipi_dbi *dbi)
+{
+	if (!dbi->reset)
+		return;
+
+	gpiod_set_value_cansleep(dbi->reset, 0);
+	usleep_range(20, 1000);
+	gpiod_set_value_cansleep(dbi->reset, 1);
+	msleep(120);
+}
+EXPORT_SYMBOL(mipi_dbi_hw_reset);
+
+/**
+ * mipi_dbi_display_is_on - Check if display is on
+ * @dbi: MIPI DBI structure
+ *
+ * This function checks the Power Mode register (if readable) to see if
+ * display output is turned on. This can be used to see if the bootloader
+ * has already turned on the display avoiding flicker when the pipeline is
+ * enabled.
+ *
+ * Returns:
+ * true if the display can be verified to be on, false otherwise.
+ */
+bool mipi_dbi_display_is_on(struct mipi_dbi *dbi)
+{
+	u8 val;
+
+	if (mipi_dbi_command_read(dbi, MIPI_DCS_GET_POWER_MODE, &val))
+		return false;
+
+	val &= ~DCS_POWER_MODE_RESERVED_MASK;
+
+	/* The poweron/reset value is 08h DCS_POWER_MODE_DISPLAY_NORMAL_MODE */
+	if (val != (DCS_POWER_MODE_DISPLAY |
+	    DCS_POWER_MODE_DISPLAY_NORMAL_MODE | DCS_POWER_MODE_SLEEP_MODE))
+		return false;
+
+	DRM_DEBUG_DRIVER("Display is ON\n");
+
+	return true;
+}
+EXPORT_SYMBOL(mipi_dbi_display_is_on);
+
+static int mipi_dbi_poweron_reset_conditional(struct mipi_dbi_dev *dbidev, bool cond)
+{
+	struct device *dev = dbidev->drm.dev;
+	struct mipi_dbi *dbi = &dbidev->dbi;
+	int ret;
+
+	if (dbidev->regulator) {
+		ret = regulator_enable(dbidev->regulator);
+		if (ret) {
+			DRM_DEV_ERROR(dev, "Failed to enable regulator (%d)\n", ret);
+			return ret;
+		}
+	}
+
+	if (cond && mipi_dbi_display_is_on(dbi))
+		return 1;
+
+	mipi_dbi_hw_reset(dbi);
+	ret = mipi_dbi_command(dbi, MIPI_DCS_SOFT_RESET);
+	if (ret) {
+		DRM_DEV_ERROR(dev, "Failed to send reset command (%d)\n", ret);
+		if (dbidev->regulator)
+			regulator_disable(dbidev->regulator);
+		return ret;
+	}
+
+	/*
+	 * If we did a hw reset, we know the controller is in Sleep mode and
+	 * per MIPI DSC spec should wait 5ms after soft reset. If we didn't,
+	 * we assume worst case and wait 120ms.
+	 */
+	if (dbi->reset)
+		usleep_range(5000, 20000);
+	else
+		msleep(120);
+
+	return 0;
+}
+
+/**
+ * mipi_dbi_poweron_reset - MIPI DBI poweron and reset
+ * @dbidev: MIPI DBI device structure
+ *
+ * This function enables the regulator if used and does a hardware and software
+ * reset.
+ *
+ * Returns:
+ * Zero on success, or a negative error code.
+ */
+int mipi_dbi_poweron_reset(struct mipi_dbi_dev *dbidev)
+{
+	return mipi_dbi_poweron_reset_conditional(dbidev, false);
+}
+EXPORT_SYMBOL(mipi_dbi_poweron_reset);
+
+/**
+ * mipi_dbi_poweron_conditional_reset - MIPI DBI poweron and conditional reset
+ * @dbidev: MIPI DBI device structure
+ *
+ * This function enables the regulator if used and if the display is off, it
+ * does a hardware and software reset. If mipi_dbi_display_is_on() determines
+ * that the display is on, no reset is performed.
+ *
+ * Returns:
+ * Zero if the controller was reset, 1 if the display was already on, or a
+ * negative error code.
+ */
+int mipi_dbi_poweron_conditional_reset(struct mipi_dbi_dev *dbidev)
+{
+	return mipi_dbi_poweron_reset_conditional(dbidev, true);
+}
+EXPORT_SYMBOL(mipi_dbi_poweron_conditional_reset);
+
+#if IS_ENABLED(CONFIG_SPI)
+
+/**
+ * mipi_dbi_spi_cmd_max_speed - get the maximum SPI bus speed
+ * @spi: SPI device
+ * @len: The transfer buffer length.
+ *
+ * Many controllers have a max speed of 10MHz, but can be pushed way beyond
+ * that. Increase reliability by running pixel data at max speed and the rest
+ * at 10MHz, preventing transfer glitches from messing up the init settings.
+ */
+u32 mipi_dbi_spi_cmd_max_speed(struct spi_device *spi, size_t len)
+{
+	if (len > 64)
+		return 0; /* use default */
+
+	return min_t(u32, 10000000, spi->max_speed_hz);
+}
+EXPORT_SYMBOL(mipi_dbi_spi_cmd_max_speed);
+
+static bool mipi_dbi_machine_little_endian(void)
+{
+#if defined(__LITTLE_ENDIAN)
+	return true;
+#else
+	return false;
+#endif
+}
+
+/*
+ * MIPI DBI Type C Option 1
+ *
+ * If the SPI controller doesn't have 9 bits per word support,
+ * use blocks of 9 bytes to send 8x 9-bit words using a 8-bit SPI transfer.
+ * Pad partial blocks with MIPI_DCS_NOP (zero).
+ * This is how the D/C bit (x) is added:
+ *     x7654321
+ *     0x765432
+ *     10x76543
+ *     210x7654
+ *     3210x765
+ *     43210x76
+ *     543210x7
+ *     6543210x
+ *     76543210
+ */
+
+static int mipi_dbi_spi1e_transfer(struct mipi_dbi *dbi, int dc,
+				   const void *buf, size_t len,
+				   unsigned int bpw)
+{
+	bool swap_bytes = (bpw == 16 && mipi_dbi_machine_little_endian());
+	size_t chunk, max_chunk = dbi->tx_buf9_len;
+	struct spi_device *spi = dbi->spi;
+	struct spi_transfer tr = {
+		.tx_buf = dbi->tx_buf9,
+		.bits_per_word = 8,
+	};
+	struct spi_message m;
+	const u8 *src = buf;
+	int i, ret;
+	u8 *dst;
+
+	if (drm_debug_enabled(DRM_UT_DRIVER))
+		pr_debug("[drm:%s] dc=%d, max_chunk=%zu, transfers:\n",
+			 __func__, dc, max_chunk);
+
+	tr.speed_hz = mipi_dbi_spi_cmd_max_speed(spi, len);
+	spi_message_init_with_transfers(&m, &tr, 1);
+
+	if (!dc) {
+		if (WARN_ON_ONCE(len != 1))
+			return -EINVAL;
+
+		/* Command: pad no-op's (zeroes) at beginning of block */
+		dst = dbi->tx_buf9;
+		memset(dst, 0, 9);
+		dst[8] = *src;
+		tr.len = 9;
+
+		return spi_sync(spi, &m);
+	}
+
+	/* max with room for adding one bit per byte */
+	max_chunk = max_chunk / 9 * 8;
+	/* but no bigger than len */
+	max_chunk = min(max_chunk, len);
+	/* 8 byte blocks */
+	max_chunk = max_t(size_t, 8, max_chunk & ~0x7);
+
+	while (len) {
+		size_t added = 0;
+
+		chunk = min(len, max_chunk);
+		len -= chunk;
+		dst = dbi->tx_buf9;
+
+		if (chunk < 8) {
+			u8 val, carry = 0;
+
+			/* Data: pad no-op's (zeroes) at end of block */
+			memset(dst, 0, 9);
+
+			if (swap_bytes) {
+				for (i = 1; i < (chunk + 1); i++) {
+					val = src[1];
+					*dst++ = carry | BIT(8 - i) | (val >> i);
+					carry = val << (8 - i);
+					i++;
+					val = src[0];
+					*dst++ = carry | BIT(8 - i) | (val >> i);
+					carry = val << (8 - i);
+					src += 2;
+				}
+				*dst++ = carry;
+			} else {
+				for (i = 1; i < (chunk + 1); i++) {
+					val = *src++;
+					*dst++ = carry | BIT(8 - i) | (val >> i);
+					carry = val << (8 - i);
+				}
+				*dst++ = carry;
+			}
+
+			chunk = 8;
+			added = 1;
+		} else {
+			for (i = 0; i < chunk; i += 8) {
+				if (swap_bytes) {
+					*dst++ =                 BIT(7) | (src[1] >> 1);
+					*dst++ = (src[1] << 7) | BIT(6) | (src[0] >> 2);
+					*dst++ = (src[0] << 6) | BIT(5) | (src[3] >> 3);
+					*dst++ = (src[3] << 5) | BIT(4) | (src[2] >> 4);
+					*dst++ = (src[2] << 4) | BIT(3) | (src[5] >> 5);
+					*dst++ = (src[5] << 3) | BIT(2) | (src[4] >> 6);
+					*dst++ = (src[4] << 2) | BIT(1) | (src[7] >> 7);
+					*dst++ = (src[7] << 1) | BIT(0);
+					*dst++ = src[6];
+				} else {
+					*dst++ =                 BIT(7) | (src[0] >> 1);
+					*dst++ = (src[0] << 7) | BIT(6) | (src[1] >> 2);
+					*dst++ = (src[1] << 6) | BIT(5) | (src[2] >> 3);
+					*dst++ = (src[2] << 5) | BIT(4) | (src[3] >> 4);
+					*dst++ = (src[3] << 4) | BIT(3) | (src[4] >> 5);
+					*dst++ = (src[4] << 3) | BIT(2) | (src[5] >> 6);
+					*dst++ = (src[5] << 2) | BIT(1) | (src[6] >> 7);
+					*dst++ = (src[6] << 1) | BIT(0);
+					*dst++ = src[7];
+				}
+
+				src += 8;
+				added++;
+			}
+		}
+
+		tr.len = chunk + added;
+
+		ret = spi_sync(spi, &m);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int mipi_dbi_spi1_transfer(struct mipi_dbi *dbi, int dc,
+				  const void *buf, size_t len,
+				  unsigned int bpw)
+{
+	struct spi_device *spi = dbi->spi;
+	struct spi_transfer tr = {
+		.bits_per_word = 9,
+	};
+	const u16 *src16 = buf;
+	const u8 *src8 = buf;
+	struct spi_message m;
+	size_t max_chunk;
+	u16 *dst16;
+	int ret;
+
+	if (!spi_is_bpw_supported(spi, 9))
+		return mipi_dbi_spi1e_transfer(dbi, dc, buf, len, bpw);
+
+	tr.speed_hz = mipi_dbi_spi_cmd_max_speed(spi, len);
+	max_chunk = dbi->tx_buf9_len;
+	dst16 = dbi->tx_buf9;
+
+	if (drm_debug_enabled(DRM_UT_DRIVER))
+		pr_debug("[drm:%s] dc=%d, max_chunk=%zu, transfers:\n",
+			 __func__, dc, max_chunk);
+
+	max_chunk = min(max_chunk / 2, len);
+
+	spi_message_init_with_transfers(&m, &tr, 1);
+	tr.tx_buf = dst16;
+
+	while (len) {
+		size_t chunk = min(len, max_chunk);
+		unsigned int i;
+
+		if (bpw == 16 && mipi_dbi_machine_little_endian()) {
+			for (i = 0; i < (chunk * 2); i += 2) {
+				dst16[i]     = *src16 >> 8;
+				dst16[i + 1] = *src16++ & 0xFF;
+				if (dc) {
+					dst16[i]     |= 0x0100;
+					dst16[i + 1] |= 0x0100;
+				}
+			}
+		} else {
+			for (i = 0; i < chunk; i++) {
+				dst16[i] = *src8++;
+				if (dc)
+					dst16[i] |= 0x0100;
+			}
+		}
+
+		tr.len = chunk * 2;
+		len -= chunk;
+
+		ret = spi_sync(spi, &m);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int mipi_dbi_typec1_command_read(struct mipi_dbi *dbi, u8 *cmd,
+					u8 *data, size_t len)
+{
+	struct spi_device *spi = dbi->spi;
+	u32 speed_hz = min_t(u32, MIPI_DBI_MAX_SPI_READ_SPEED,
+			     spi->max_speed_hz / 2);
+	struct spi_transfer tr[2] = {
+		{
+			.speed_hz = speed_hz,
+			.bits_per_word = 9,
+			.tx_buf = dbi->tx_buf9,
+			.len = 2,
+		}, {
+			.speed_hz = speed_hz,
+			.bits_per_word = 8,
+			.len = len,
+			.rx_buf = data,
+		},
+	};
+	struct spi_message m;
+	u16 *dst16;
+	int ret;
+
+	if (!len)
+		return -EINVAL;
+
+	if (!spi_is_bpw_supported(spi, 9)) {
+		/*
+		 * FIXME: implement something like mipi_dbi_spi1e_transfer() but
+		 * for reads using emulation.
+		 */
+		dev_err(&spi->dev,
+			"reading on host not supporting 9 bpw not yet implemented\n");
+		return -EOPNOTSUPP;
+	}
+
+	/*
+	 * Turn the 8bit command into a 16bit version of the command in the
+	 * buffer. Only 9 bits of this will be used when executing the actual
+	 * transfer.
+	 */
+	dst16 = dbi->tx_buf9;
+	dst16[0] = *cmd;
+
+	spi_message_init_with_transfers(&m, tr, ARRAY_SIZE(tr));
+	ret = spi_sync(spi, &m);
+
+	if (!ret)
+		MIPI_DBI_DEBUG_COMMAND(*cmd, data, len);
+
+	return ret;
+}
+
+static int mipi_dbi_typec1_command(struct mipi_dbi *dbi, u8 *cmd,
+				   u8 *parameters, size_t num)
+{
+	unsigned int bpw = (*cmd == MIPI_DCS_WRITE_MEMORY_START) ? 16 : 8;
+	int ret;
+
+	if (mipi_dbi_command_is_read(dbi, *cmd))
+		return mipi_dbi_typec1_command_read(dbi, cmd, parameters, num);
+
+	MIPI_DBI_DEBUG_COMMAND(*cmd, parameters, num);
+
+	ret = mipi_dbi_spi1_transfer(dbi, 0, cmd, 1, 8);
+	if (ret || !num)
+		return ret;
+
+	return mipi_dbi_spi1_transfer(dbi, 1, parameters, num, bpw);
+}
+
+/* MIPI DBI Type C Option 3 */
+
+static int mipi_dbi_typec3_command_read(struct mipi_dbi *dbi, u8 *cmd,
+					u8 *data, size_t len)
+{
+	struct spi_device *spi = dbi->spi;
+	u32 speed_hz = min_t(u32, MIPI_DBI_MAX_SPI_READ_SPEED,
+			     spi->max_speed_hz / 2);
+	struct spi_transfer tr[2] = {
+		{
+			.speed_hz = speed_hz,
+			.tx_buf = cmd,
+			.len = 1,
+		}, {
+			.speed_hz = speed_hz,
+			.len = len,
+		},
+	};
+	struct spi_message m;
+	u8 *buf;
+	int ret;
+
+	if (!len)
+		return -EINVAL;
+
+	/*
+	 * Support non-standard 24-bit and 32-bit Nokia read commands which
+	 * start with a dummy clock, so we need to read an extra byte.
+	 */
+	if (*cmd == MIPI_DCS_GET_DISPLAY_ID ||
+	    *cmd == MIPI_DCS_GET_DISPLAY_STATUS) {
+		if (!(len == 3 || len == 4))
+			return -EINVAL;
+
+		tr[1].len = len + 1;
+	}
+
+	buf = kmalloc(tr[1].len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	tr[1].rx_buf = buf;
+	gpiod_set_value_cansleep(dbi->dc, 0);
+
+	spi_message_init_with_transfers(&m, tr, ARRAY_SIZE(tr));
+	ret = spi_sync(spi, &m);
+	if (ret)
+		goto err_free;
+
+	if (tr[1].len == len) {
+		memcpy(data, buf, len);
+	} else {
+		unsigned int i;
+
+		for (i = 0; i < len; i++)
+			data[i] = (buf[i] << 1) | (buf[i + 1] >> 7);
+	}
+
+	MIPI_DBI_DEBUG_COMMAND(*cmd, data, len);
+
+err_free:
+	kfree(buf);
+
+	return ret;
+}
+
+static int mipi_dbi_typec3_command(struct mipi_dbi *dbi, u8 *cmd,
+				   u8 *par, size_t num)
+{
+	struct spi_device *spi = dbi->spi;
+	unsigned int bpw = 8;
+	u32 speed_hz;
+	int ret;
+
+	if (mipi_dbi_command_is_read(dbi, *cmd))
+		return mipi_dbi_typec3_command_read(dbi, cmd, par, num);
+
+	MIPI_DBI_DEBUG_COMMAND(*cmd, par, num);
+
+	gpiod_set_value_cansleep(dbi->dc, 0);
+	speed_hz = mipi_dbi_spi_cmd_max_speed(spi, 1);
+	ret = mipi_dbi_spi_transfer(spi, speed_hz, 8, cmd, 1);
+	if (ret || !num)
+		return ret;
+
+	if (*cmd == MIPI_DCS_WRITE_MEMORY_START && !dbi->swap_bytes)
+		bpw = 16;
+
+	gpiod_set_value_cansleep(dbi->dc, 1);
+	speed_hz = mipi_dbi_spi_cmd_max_speed(spi, num);
+
+	return mipi_dbi_spi_transfer(spi, speed_hz, bpw, par, num);
+}
+
+/**
+ * mipi_dbi_spi_init - Initialize MIPI DBI SPI interface
+ * @spi: SPI device
+ * @dbi: MIPI DBI structure to initialize
+ * @dc: D/C gpio (optional)
+ *
+ * This function sets &mipi_dbi->command, enables &mipi_dbi->read_commands for the
+ * usual read commands. It should be followed by a call to mipi_dbi_dev_init() or
+ * a driver-specific init.
+ *
+ * If @dc is set, a Type C Option 3 interface is assumed, if not
+ * Type C Option 1.
+ *
+ * If the SPI master driver doesn't support the necessary bits per word,
+ * the following transformation is used:
+ *
+ * - 9-bit: reorder buffer as 9x 8-bit words, padded with no-op command.
+ * - 16-bit: if big endian send as 8-bit, if little endian swap bytes
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *dbi,
+		      struct gpio_desc *dc)
+{
+	struct device *dev = &spi->dev;
+	int ret;
+
+	/*
+	 * Even though it's not the SPI device that does DMA (the master does),
+	 * the dma mask is necessary for the dma_alloc_wc() in the GEM code
+	 * (e.g., drm_gem_dma_create()). The dma_addr returned will be a physical
+	 * address which might be different from the bus address, but this is
+	 * not a problem since the address will not be used.
+	 * The virtual address is used in the transfer and the SPI core
+	 * re-maps it on the SPI master device using the DMA streaming API
+	 * (spi_map_buf()).
+	 */
+	if (!dev->coherent_dma_mask) {
+		ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
+		if (ret) {
+			dev_warn(dev, "Failed to set dma mask %d\n", ret);
+			return ret;
+		}
+	}
+
+	dbi->spi = spi;
+	dbi->read_commands = mipi_dbi_dcs_read_commands;
+
+	if (dc) {
+		dbi->command = mipi_dbi_typec3_command;
+		dbi->dc = dc;
+		if (mipi_dbi_machine_little_endian() && !spi_is_bpw_supported(spi, 16))
+			dbi->swap_bytes = true;
+	} else {
+		dbi->command = mipi_dbi_typec1_command;
+		dbi->tx_buf9_len = SZ_16K;
+		dbi->tx_buf9 = devm_kmalloc(dev, dbi->tx_buf9_len, GFP_KERNEL);
+		if (!dbi->tx_buf9)
+			return -ENOMEM;
+	}
+
+	mutex_init(&dbi->cmdlock);
+
+	DRM_DEBUG_DRIVER("SPI speed: %uMHz\n", spi->max_speed_hz / 1000000);
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dbi_spi_init);
+
+/**
+ * mipi_dbi_spi_transfer - SPI transfer helper
+ * @spi: SPI device
+ * @speed_hz: Override speed (optional)
+ * @bpw: Bits per word
+ * @buf: Buffer to transfer
+ * @len: Buffer length
+ *
+ * This SPI transfer helper breaks up the transfer of @buf into chunks which
+ * the SPI controller driver can handle.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_spi_transfer(struct spi_device *spi, u32 speed_hz,
+			  u8 bpw, const void *buf, size_t len)
+{
+	size_t max_chunk = spi_max_transfer_size(spi);
+	struct spi_transfer tr = {
+		.bits_per_word = bpw,
+		.speed_hz = speed_hz,
+	};
+	struct spi_message m;
+	size_t chunk;
+	int ret;
+
+	/* In __spi_validate, there's a validation that no partial transfers
+	 * are accepted (xfer->len % w_size must be zero).
+	 * Here we align max_chunk to multiple of 2 (16bits),
+	 * to prevent transfers from being rejected.
+	 */
+	max_chunk = ALIGN_DOWN(max_chunk, 2);
+
+	spi_message_init_with_transfers(&m, &tr, 1);
+
+	while (len) {
+		chunk = min(len, max_chunk);
+
+		tr.tx_buf = buf;
+		tr.len = chunk;
+		buf += chunk;
+		len -= chunk;
+
+		ret = spi_sync(spi, &m);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dbi_spi_transfer);
+
+#endif /* CONFIG_SPI */
+
+#ifdef CONFIG_DEBUG_FS
+
+static ssize_t mipi_dbi_debugfs_command_write(struct file *file,
+					      const char __user *ubuf,
+					      size_t count, loff_t *ppos)
+{
+	struct seq_file *m = file->private_data;
+	struct mipi_dbi_dev *dbidev = m->private;
+	u8 val, cmd = 0, parameters[64];
+	char *buf, *pos, *token;
+	int i, ret, idx;
+
+	if (!drm_dev_enter(&dbidev->drm, &idx))
+		return -ENODEV;
+
+	buf = memdup_user_nul(ubuf, count);
+	if (IS_ERR(buf)) {
+		ret = PTR_ERR(buf);
+		goto err_exit;
+	}
+
+	/* strip trailing whitespace */
+	for (i = count - 1; i > 0; i--)
+		if (isspace(buf[i]))
+			buf[i] = '\0';
+		else
+			break;
+	i = 0;
+	pos = buf;
+	while (pos) {
+		token = strsep(&pos, " ");
+		if (!token) {
+			ret = -EINVAL;
+			goto err_free;
+		}
+
+		ret = kstrtou8(token, 16, &val);
+		if (ret < 0)
+			goto err_free;
+
+		if (token == buf)
+			cmd = val;
+		else
+			parameters[i++] = val;
+
+		if (i == 64) {
+			ret = -E2BIG;
+			goto err_free;
+		}
+	}
+
+	ret = mipi_dbi_command_buf(&dbidev->dbi, cmd, parameters, i);
+
+err_free:
+	kfree(buf);
+err_exit:
+	drm_dev_exit(idx);
+
+	return ret < 0 ? ret : count;
+}
+
+static int mipi_dbi_debugfs_command_show(struct seq_file *m, void *unused)
+{
+	struct mipi_dbi_dev *dbidev = m->private;
+	struct mipi_dbi *dbi = &dbidev->dbi;
+	u8 cmd, val[4];
+	int ret, idx;
+	size_t len;
+
+	if (!drm_dev_enter(&dbidev->drm, &idx))
+		return -ENODEV;
+
+	for (cmd = 0; cmd < 255; cmd++) {
+		if (!mipi_dbi_command_is_read(dbi, cmd))
+			continue;
+
+		switch (cmd) {
+		case MIPI_DCS_READ_MEMORY_START:
+		case MIPI_DCS_READ_MEMORY_CONTINUE:
+			len = 2;
+			break;
+		case MIPI_DCS_GET_DISPLAY_ID:
+			len = 3;
+			break;
+		case MIPI_DCS_GET_DISPLAY_STATUS:
+			len = 4;
+			break;
+		default:
+			len = 1;
+			break;
+		}
+
+		seq_printf(m, "%02x: ", cmd);
+		ret = mipi_dbi_command_buf(dbi, cmd, val, len);
+		if (ret) {
+			seq_puts(m, "XX\n");
+			continue;
+		}
+		seq_printf(m, "%*phN\n", (int)len, val);
+	}
+
+	drm_dev_exit(idx);
+
+	return 0;
+}
+
+static int mipi_dbi_debugfs_command_open(struct inode *inode,
+					 struct file *file)
+{
+	return single_open(file, mipi_dbi_debugfs_command_show,
+			   inode->i_private);
+}
+
+static const struct file_operations mipi_dbi_debugfs_command_fops = {
+	.owner = THIS_MODULE,
+	.open = mipi_dbi_debugfs_command_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = mipi_dbi_debugfs_command_write,
+};
+
+/**
+ * mipi_dbi_debugfs_init - Create debugfs entries
+ * @minor: DRM minor
+ *
+ * This function creates a 'command' debugfs file for sending commands to the
+ * controller or getting the read command values.
+ * Drivers can use this as their &drm_driver->debugfs_init callback.
+ *
+ */
+void mipi_dbi_debugfs_init(struct drm_minor *minor)
+{
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(minor->dev);
+	umode_t mode = S_IFREG | S_IWUSR;
+
+	if (dbidev->dbi.read_commands)
+		mode |= S_IRUGO;
+	debugfs_create_file("command", mode, minor->debugfs_root, dbidev,
+			    &mipi_dbi_debugfs_command_fops);
+}
+EXPORT_SYMBOL(mipi_dbi_debugfs_init);
+
+#endif
+
+MODULE_LICENSE("GPL");