[PATCH 0/3] Add support for Sitronix ST7571 LCD controller

[PATCH 0/3] Add support for Sitronix ST7571 LCD controller

[Marcus Folkesson]

This series add support for the ST7571 LCD Controller.
It is a 4 gray scale dot matrix LCD controller that supports several
interfaces such as SPI, I2C and a 8bit parallell port.

This driver only supports the I2C interface, but all common parts could
easily be put into a common file to be used with other interfaces.
I only have I2C to test with.

The device is a little defiant, it tends to NAK some commands, but all
commands takes effect, hence the I2C_M_IGNORE_NAK flag.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---
Marcus Folkesson (3):
      dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings
      drm/st7571-i2c: add support for Sitronix ST7571 LCD controller
      MAINTAINERS: add antry for Sitronix ST7571 LCD controller

 .../bindings/display/sitronix,st7571-i2c.yaml      |  71 +++
 MAINTAINERS                                        |   7 +
 drivers/gpu/drm/tiny/Kconfig                       |  12 +
 drivers/gpu/drm/tiny/Makefile                      |   1 +
 drivers/gpu/drm/tiny/st7571-i2c.c                  | 563 +++++++++++++++++++++
 5 files changed, 654 insertions(+)
---
base-commit: 1e26c5e28ca5821a824e90dd359556f5e9e7b89f
change-id: 20250401-st7571-9382b9cfc03f

Best regards,
-- 
Marcus Folkesson <marcus.folkesson@gmail.com>

[PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Marcus Folkesson]

Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
The controller has a SPI, I2C and 8bit parallel interface, this is for
the I2C interface only.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---
 .../bindings/display/sitronix,st7571-i2c.yaml      | 71 ++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..6e5e0994a98db646a37bb17c4289332546c9266e
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
@@ -0,0 +1,71 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/sitronix,st7571-i2c.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sitronix ST7571 Display Panels
+
+maintainers:
+  - Marcus Folkesson <marcus.folkesson@gmail.com>
+
+properties:
+  compatible:
+    const: sitronix,st7571-i2c
+
+  reg:
+    description: I2C address of the LCD controller
+    maxItems: 1
+
+  sitronix,panel-width-mm:
+    description: physical panel width [mm]
+
+  sitronix,panel-height-mm:
+    description: physical panel height [mm]
+
+  sitronix,panel-nlines:
+    description: Number of lines in the panel
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 128
+    default: 128
+
+  sitronix,panel-start-line:
+    description: Start line of the panel
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 0
+    maximum: 127
+    default: 0
+
+  reset-gpios:
+    description: GPIO connected to the RST_N signal.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - reset-gpios
+  - sitronix,panel-width-mm
+  - sitronix,panel-height-mm
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        display@3f {
+          compatible = "sitronix,st7571-i2c";
+          reg = <0x3f>;
+
+          reset-gpios = <&gpio0 3 GPIO_ACTIVE_HIGH>;
+          sitronix,panel-width-mm = <37>;
+          sitronix,panel-height-mm = <27>;
+          sitronix,panel-nlines = <96>;
+          sitronix,panel-start-line = <0>;
+        };
+    };

-- 
2.48.1

[PATCH 2/3] drm/st7571-i2c: add support for Sitronix ST7571 LCD controller

[Marcus Folkesson]

Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
The controller has a SPI, I2C and 8bit parallel interface, this
driver is for the I2C interface only.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---
 drivers/gpu/drm/tiny/Kconfig      |  12 +
 drivers/gpu/drm/tiny/Makefile     |   1 +
 drivers/gpu/drm/tiny/st7571-i2c.c | 563 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 576 insertions(+)

diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
index 94cbdb1337c07f1628a33599a7130369b9d59d98..14096031e7c2d8f73c06c88e08f35aa5a3790a54 100644
--- a/drivers/gpu/drm/tiny/Kconfig
+++ b/drivers/gpu/drm/tiny/Kconfig
@@ -232,6 +232,18 @@ config TINYDRM_ST7586
 
 	  If M is selected the module will be called st7586.
 
+config TINYDRM_ST7571_I2C
+	tristate "DRM support for Sitronix ST7571 display panels (I2C)"
+	depends on DRM && I2C
+	select DRM_KMS_HELPER
+	select DRM_GEM_DMA_HELPER
+	select DRM_GEM_SHMEM_HELPER
+	select REGMAP_I2C
+	help
+	  DRM driver for Sitronix ST7571 panels controlled over I2C.
+
+	  if M is selected the module will be called st7571-i2c.
+
 config TINYDRM_ST7735R
 	tristate "DRM support for Sitronix ST7715R/ST7735R display panels"
 	depends on DRM && SPI
diff --git a/drivers/gpu/drm/tiny/Makefile b/drivers/gpu/drm/tiny/Makefile
index 60816d2eb4ff93b87228ed8eadd60a0a33a1144b..343813a965e13326bbb8520a5c34d272ec7821d5 100644
--- a/drivers/gpu/drm/tiny/Makefile
+++ b/drivers/gpu/drm/tiny/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_TINYDRM_REPAPER)		+= repaper.o
 obj-$(CONFIG_TINYDRM_SHARP_MEMORY)	+= sharp-memory.o
 obj-$(CONFIG_TINYDRM_ST7586)		+= st7586.o
 obj-$(CONFIG_TINYDRM_ST7735R)		+= st7735r.o
+obj-$(CONFIG_TINYDRM_ST7571_I2C)	+= st7571-i2c.o
diff --git a/drivers/gpu/drm/tiny/st7571-i2c.c b/drivers/gpu/drm/tiny/st7571-i2c.c
new file mode 100644
index 0000000000000000000000000000000000000000..c26ecf8a4fd2115b808b126cccda74ea9079cd7c
--- /dev/null
+++ b/drivers/gpu/drm/tiny/st7571-i2c.c
@@ -0,0 +1,563 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for Sitronix ST7571, a 4 level gray scale dot matrix LCD controller
+ *
+ * Copyright (C) 2025 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <drm/clients/drm_client_setup.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_damage_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_fbdev_dma.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_module.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_simple_kms_helper.h>
+
+#define ST7571_COMMAND_MODE			(0x00)
+#define ST7571_DATA_MODE			(0x40)
+
+/* Normal mode command set */
+#define ST7571_DISPLAY_OFF			(0xae)
+#define ST7571_DISPLAY_ON			(0xaf)
+#define ST7571_OSC_ON				(0xab)
+#define ST7571_SET_COLUMN_LSB(c)		(0x00 | ((c) & 0xf))
+#define ST7571_SET_COLUMN_MSB(c)		(0x10 | ((c) >> 4))
+#define ST7571_SET_COM0_LSB(x)			((x) & 0x7f)
+#define ST7571_SET_COM0_MSB			(0x44)
+#define ST7571_SET_COM_SCAN_DIR(d)		(0xc0 | (((d) << 3) & 0x8))
+#define ST7571_SET_CONTRAST_LSB(c)		((c) & 0x3f)
+#define ST7571_SET_CONTRAST_MSB			(0x81)
+#define ST7571_SET_DISPLAY_DUTY_LSB(d)		((d) & 0xff)
+#define ST7571_SET_DISPLAY_DUTY_MSB		(0x48)
+#define ST7571_SET_ENTIRE_DISPLAY_ON(p)		(0xa4 | ((p) & 0x1))
+#define ST7571_SET_LCD_BIAS(b)			(0x50 | ((b) & 0x7))
+#define ST7571_SET_MODE_LSB(m)			((m) & 0xfc)
+#define ST7571_SET_MODE_MSB			(0x38)
+#define ST7571_SET_PAGE(p)			(0xb0 | (p))
+#define ST7571_SET_POWER(p)			(0x28 | ((p) & 0x7))
+#define ST7571_SET_REGULATOR_REG(r)		(0x20 | ((r) & 0x7))
+#define ST7571_SET_REVERSE(r)			(0xa6 | ((r) & 0x1))
+#define ST7571_SET_SEG_SCAN_DIR(d)		(0xa0 | ((d) & 0x1))
+#define ST7571_SET_START_LINE_LSB(l)		((l) & 0x3f)
+#define ST7571_SET_START_LINE_MSB		(0x40)
+
+/* Extension command set 3 */
+#define ST7571_COMMAND_SET_3			(0x7b)
+#define ST7571_SET_COLOR_MODE(c)		(0x10 | ((c) & 0x1))
+#define ST7571_COLOR_MODE_BLACKWHITE		(1)
+#define ST7571_COLOR_MODE_GRAY			(0)
+#define ST7571_COMMAND_SET_NORMAL		(0x00)
+
+#define DRIVER_NAME "st7571-i2c"
+#define DRIVER_DESC "ST7571 DRM driver"
+#define DRIVER_MAJOR 1
+#define DRIVER_MINOR 0
+
+#define to_st7571(_dev) container_of(_dev, struct st7571_device, dev)
+
+struct st7571_device {
+	struct drm_device	       dev;
+	struct drm_simple_display_pipe pipe;
+	struct drm_connector	       conn;
+	struct drm_display_mode mode;
+	struct regmap *regmap;
+	struct i2c_client *client;
+	struct gpio_desc *reset;
+	u8 bpp;
+	u32 width_mm;
+	u32 height_mm;
+	u32 nlines;
+	u32 startline;
+	bool ignore_nak;
+};
+
+static int st7571_regmap_write(void *context, const void *data, size_t count)
+{
+	struct i2c_client *client = context;
+	struct st7571_device *st7571 = i2c_get_clientdata(client);
+	int ret;
+
+	struct i2c_msg msg = {
+		.addr = st7571->client->addr,
+		.flags = st7571->ignore_nak ? I2C_M_IGNORE_NAK : 0,
+		.len = count,
+		.buf = (u8 *)data
+	};
+
+	ret = i2c_transfer(st7571->client->adapter, &msg, 1);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int st7571_regmap_read(void *context, const void *reg_buf,
+			       size_t reg_size, void *val_buf, size_t val_size)
+{
+	return -EOPNOTSUPP;
+}
+
+static int st7571_send_command_list(struct st7571_device *st7571,
+				    const u8 *cmd_list, size_t len)
+{
+	int ret;
+
+	for (int i = 0; i < len; i++) {
+		ret = regmap_write(st7571->regmap, ST7571_COMMAND_MODE, cmd_list[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return ret;
+}
+
+static inline u8 st7571_transform_xy(const char *p, int x, int y)
+{
+	int xrest = x % 8;
+	u8 result = 0;
+
+	/*
+	 * Transforms an (x, y) pixel coordinate into a vertical 8-bit
+	 * column from the framebuffer. It calculates the corresponding byte in the
+	 * framebuffer, extracts the bit at the given x position across 8 consecutive
+	 * rows, and packs those bits into a single byte.
+	 *
+	 * Return an 8-bit value representing a vertical column of pixels.
+	 */
+	x = x / 8;
+	y = (y / 8) * 8;
+
+	for (int i = 0; i < 8; i++) {
+		int row_idx = y + i;
+		u8 byte = p[row_idx * 16 + x];
+		u8 bit = (byte >> (7-xrest)) & 1;
+
+		result |= (bit << i);
+	}
+
+	return result;
+}
+
+static int st7571_set_position(struct st7571_device *st7571, int x, int y)
+{
+	u8 cmd_list[] = {
+		ST7571_SET_COLUMN_LSB(x),
+		ST7571_SET_COLUMN_MSB(x),
+		ST7571_SET_PAGE(y/8),
+	};
+
+	return st7571_send_command_list(st7571, cmd_list, ARRAY_SIZE(cmd_list));
+}
+
+static int st7571_fb_blit_rect(struct drm_framebuffer *fb,
+			       const struct iosys_map *vmap,
+			       struct drm_rect *rect)
+{
+	struct st7571_device *st7571 = to_st7571(fb->dev);
+
+	char row[256];
+	char *pixel = vmap->vaddr;
+	int x1 = rect->x1 * st7571->bpp;
+	int x2 = rect->x2 * st7571->bpp;
+
+	for (int y = rect->y1; y < rect->y2; y += 8) {
+		for (int x = x1; x < x2; x++)
+			row[x] = st7571_transform_xy(pixel, x, y);
+
+		st7571_set_position(st7571, rect->x1, y);
+
+		/* TODO: Investige why we can't write multiple bytes at once */
+		for (int x = x1; x < x2; x++)
+			regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);
+	}
+
+	return 0;
+}
+
+static int st7571_fb_blit_fullscreen(struct drm_framebuffer *fb,
+				     const struct iosys_map *map)
+{
+	struct drm_rect fullscreen = {
+		.x1 = 0,
+		.x2 = fb->width,
+		.y1 = 0,
+		.y2 = fb->height,
+	};
+
+	return st7571_fb_blit_rect(fb, map, &fullscreen);
+}
+
+static int st7571_conn_get_modes(struct drm_connector *conn)
+{
+	struct st7571_device *st7571 = to_st7571(conn->dev);
+
+	return drm_connector_helper_get_modes_fixed(conn, &st7571->mode);
+}
+
+static const struct drm_connector_helper_funcs st7571_conn_helper_funcs = {
+	.get_modes = st7571_conn_get_modes,
+};
+
+static const struct drm_connector_funcs st7571_conn_funcs = {
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static int st7571_conn_init(struct st7571_device *st7571)
+{
+	drm_connector_helper_add(&st7571->conn, &st7571_conn_helper_funcs);
+	return drm_connector_init(&st7571->dev, &st7571->conn,
+				  &st7571_conn_funcs, DRM_MODE_CONNECTOR_Unknown);
+
+}
+
+
+static void st7571_pipe_enable(struct drm_simple_display_pipe *pipe,
+			       struct drm_crtc_state *crtc_state,
+			       struct drm_plane_state *plane_state)
+{
+	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
+
+	st7571_fb_blit_fullscreen(plane_state->fb, &shadow_plane_state->data[0]);
+}
+
+static void st7571_pipe_update(struct drm_simple_display_pipe *pipe,
+			       struct drm_plane_state *old_state)
+{
+	struct drm_plane_state *state = pipe->plane.state;
+	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
+	struct drm_rect rect;
+
+	if (state->fb && drm_atomic_helper_damage_merged(old_state, state, &rect))
+		st7571_fb_blit_rect(state->fb, &shadow_plane_state->data[0], &rect);
+}
+
+static const struct drm_simple_display_pipe_funcs st7571_pipe_funcs = {
+	.enable	    = st7571_pipe_enable,
+	.update	    = st7571_pipe_update,
+	DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
+};
+
+static const uint32_t st7571_formats[] = {
+	DRM_FORMAT_C1,
+	DRM_FORMAT_C2,
+};
+
+static const uint64_t st7571_modifiers[] = {
+	DRM_FORMAT_MOD_LINEAR,
+	DRM_FORMAT_MOD_INVALID
+};
+
+static int st7571_pipe_init(struct st7571_device *st7571)
+{
+	return drm_simple_display_pipe_init(&st7571->dev,
+					    &st7571->pipe,
+					    &st7571_pipe_funcs,
+					    st7571_formats,
+					    ARRAY_SIZE(st7571_formats),
+					    st7571_modifiers,
+					    &st7571->conn);
+}
+
+static int st7571_set_pixel_format(struct st7571_device *st7571,
+				   u32 pixel_format)
+{
+	u8 cmd_list[] = {
+		ST7571_COMMAND_SET_3,
+		ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_BLACKWHITE),
+		ST7571_COMMAND_SET_NORMAL,
+	};
+
+	switch (pixel_format) {
+	case DRM_FORMAT_C1:
+		cmd_list[1] = ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_BLACKWHITE);
+		st7571->bpp = 1;
+		break;
+	case DRM_FORMAT_C2:
+		cmd_list[1] = ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_GRAY);
+		st7571->bpp = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return st7571_send_command_list(st7571, cmd_list, ARRAY_SIZE(cmd_list));
+}
+
+static struct drm_framebuffer*
+st7571_fb_create(struct drm_device *dev, struct drm_file *file_priv,
+		 const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	int ret = st7571_set_pixel_format(to_st7571(dev), mode_cmd->pixel_format);
+
+	if (ret)
+		return ERR_PTR(ret);
+
+	return drm_gem_fb_create_with_dirty(dev, file_priv, mode_cmd);
+}
+
+static const struct drm_mode_config_funcs st7571_mode_config_funcs = {
+	.fb_create = st7571_fb_create,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+static int st7571_mode_config_init(struct st7571_device *st7571)
+{
+	struct drm_device *dev = &st7571->dev;
+	int ret;
+
+	ret = drmm_mode_config_init(dev);
+	if (ret)
+		return ret;
+
+	dev->mode_config.min_width = 0;
+	dev->mode_config.min_height = 0;
+	dev->mode_config.max_width = 128;
+	dev->mode_config.max_height = 128;
+	dev->mode_config.preferred_depth = 1;
+	dev->mode_config.prefer_shadow = 0;
+	dev->mode_config.funcs = &st7571_mode_config_funcs;
+
+	return 0;
+}
+
+DEFINE_DRM_GEM_FOPS(st7571_fops);
+
+static const struct drm_driver st7571_driver = {
+	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
+
+	.name		 = DRIVER_NAME,
+	.desc		 = DRIVER_DESC,
+	.major		 = DRIVER_MAJOR,
+	.minor		 = DRIVER_MINOR,
+
+	.fops		 = &st7571_fops,
+	DRM_GEM_SHMEM_DRIVER_OPS,
+	DRM_FBDEV_DMA_DRIVER_OPS,
+};
+
+static const struct regmap_bus st7571_regmap_bus = {
+	.read = st7571_regmap_read,
+	.write = st7571_regmap_write,
+};
+
+static const struct regmap_config st7571_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.use_single_write = true,
+};
+
+static int st7571_parse_dt(struct st7571_device *st7571)
+{
+	struct device *dev = &st7571->client->dev;
+	struct device_node *np = dev->of_node;
+
+	of_property_read_u32(np, "sitronix,panel-width-mm", &st7571->width_mm);
+	of_property_read_u32(np, "sitronix,panel-height-mm", &st7571->height_mm);
+	of_property_read_u32(np, "sitronix,panel-start-line", &st7571->startline);
+	of_property_read_u32(np, "sitronix,panel-nlines", &st7571->nlines);
+
+	if (st7571->width_mm == 0 || st7571->height_mm == 0) {
+		dev_err(dev, "Invalid panel dimensions\n");
+		return -EINVAL;
+	}
+
+	/* Default to 128 lines if not specified */
+	if (!st7571->nlines)
+		st7571->nlines = 128;
+
+	if (st7571->startline + st7571->nlines > 128) {
+		dev_err(dev, "Invalid line configuration (start-line=%i, nlines=%i)\n",
+			st7571->startline, st7571->nlines);
+		return -EINVAL;
+	}
+
+	st7571->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(st7571->reset))
+		return PTR_ERR(st7571->reset);
+
+	return 0;
+}
+
+static void st7571_create_mode(struct st7571_device *st7571)
+{
+	struct drm_display_mode st7571_mode = {
+		DRM_SIMPLE_MODE(128, st7571->nlines, st7571->width_mm, st7571->height_mm),
+	};
+
+	memcpy(&st7571->mode, &st7571_mode, sizeof(st7571_mode));
+}
+
+static void st7571_reset(struct st7571_device *st7571)
+{
+	gpiod_set_value_cansleep(st7571->reset, 0);
+	mdelay(20);
+	gpiod_set_value_cansleep(st7571->reset, 1);
+}
+
+static int st7571_initialize(struct st7571_device *st7571)
+{
+	/*
+	 * Most of the initialization sequence is taken directly from the
+	 * referential initial code in the ST7571 datasheet.
+	 */
+	u8 commands[] = {
+		ST7571_DISPLAY_OFF,
+		ST7571_SET_MODE_MSB,
+
+		ST7571_SET_MODE_LSB(0x94),
+		ST7571_SET_SEG_SCAN_DIR(0),
+		ST7571_SET_COM_SCAN_DIR(1),
+
+		ST7571_SET_COM0_MSB,
+		ST7571_SET_COM0_LSB(0x00),
+
+		ST7571_SET_START_LINE_MSB,
+		ST7571_SET_START_LINE_LSB(st7571->startline),
+
+		ST7571_OSC_ON,
+		ST7571_SET_REGULATOR_REG(5),
+		ST7571_SET_CONTRAST_MSB,
+		ST7571_SET_CONTRAST_LSB(0x33),
+		ST7571_SET_LCD_BIAS(0x04),
+		ST7571_SET_DISPLAY_DUTY_MSB,
+		ST7571_SET_DISPLAY_DUTY_LSB(st7571->nlines),
+
+
+		ST7571_SET_POWER(0x4),	/* Power Control, VC: ON, VR: OFF, VF: OFF */
+		ST7571_SET_POWER(0x6),	/* Power Control, VC: ON, VR: ON, VF: OFF */
+		ST7571_SET_POWER(0x7),	/* Power Control, VC: ON, VR: ON, VF: ON */
+
+		ST7571_SET_REVERSE(0),
+		ST7571_SET_ENTIRE_DISPLAY_ON(0),
+
+		ST7571_DISPLAY_ON,
+	};
+
+	/* Perform a reset before initializing the controller */
+	st7571_reset(st7571);
+
+	return st7571_send_command_list(st7571, commands, ARRAY_SIZE(commands));
+}
+
+
+static int st7571_probe(struct i2c_client *client)
+{
+	struct drm_device *dev;
+	struct st7571_device *st7571;
+	int ret;
+
+	st7571 = devm_drm_dev_alloc(&client->dev, &st7571_driver,
+				    struct st7571_device, dev);
+	if (IS_ERR(st7571))
+		return PTR_ERR(st7571);
+
+	dev = &st7571->dev;
+	st7571->client = client;
+	i2c_set_clientdata(client, st7571);
+
+	ret = st7571_parse_dt(st7571);
+	if (ret)
+		return ret;
+
+	/* Create mode with parsed values */
+	st7571_create_mode(st7571);
+
+	/*
+	 * The chip nacks some messages but still works as expected.
+	 * If the adapter does not support protocol mangling do
+	 * not set the I2C_M_IGNORE_NAK flag at the expense * of possible
+	 * cruft in the logs.
+	 */
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_PROTOCOL_MANGLING))
+		st7571->ignore_nak = true;
+
+	st7571->regmap = devm_regmap_init(&client->dev, &st7571_regmap_bus,
+					   client, &st7571_regmap_config);
+	if (IS_ERR(st7571->regmap)) {
+		dev_err(&client->dev, "Failed to initialize regmap\n");
+		return PTR_ERR(st7571->regmap);
+	}
+
+	ret = st7571_initialize(st7571);
+	if (ret)
+		return ret;
+
+	ret = st7571_mode_config_init(st7571);
+	if (ret)
+		return ret;
+
+	ret = st7571_conn_init(st7571);
+	if (ret < 0)
+		return ret;
+
+	ret = st7571_pipe_init(st7571);
+	if (ret < 0)
+		return ret;
+
+	drm_plane_enable_fb_damage_clips(&st7571->pipe.plane);
+	drm_mode_config_reset(dev);
+
+	ret = drm_dev_register(dev, 0);
+	if (ret)
+		return ret;
+
+	drm_client_setup(dev, NULL);
+	return 0;
+}
+
+static void st7571_remove(struct i2c_client *client)
+{
+	struct st7571_device *st7571 = i2c_get_clientdata(client);
+
+	drm_dev_unplug(&st7571->dev);
+	drm_atomic_helper_shutdown(&st7571->dev);
+}
+
+static const struct of_device_id st7571_of_match[] = {
+	{ .compatible = "sitronix,st7571-i2c" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, st7571_of_match);
+
+
+static const struct i2c_device_id st7571_id[] = {
+	{ "st7571-i2c", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, st7571_id);
+
+static struct i2c_driver st7571_i2c_driver = {
+	.driver = {
+		.name = "st7571-i2c",
+		.of_match_table = st7571_of_match,
+	},
+	.probe = st7571_probe,
+	.remove = st7571_remove,
+	.id_table = st7571_id,
+};
+
+module_i2c_driver(st7571_i2c_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("DRM Driver for Sitronix ST7571 LCD controller");
+MODULE_LICENSE("GPL");

-- 
2.48.1

[PATCH 3/3] MAINTAINERS: add antry for Sitronix ST7571 LCD controller

[Marcus Folkesson]

Add MAINTAINERS entry for the Sitronix ST7571 dot matrix LCD
controller.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---
 MAINTAINERS | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 889bd4a59551c9bc125f94944a6e1c7e3ef2de83..00d19d45679f6d18a7e9c9e619b7642176b7ef95 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7572,6 +7572,13 @@ T:	git https://gitlab.freedesktop.org/drm/misc/kernel.git
 F:	Documentation/devicetree/bindings/display/sitronix,st7586.txt
 F:	drivers/gpu/drm/tiny/st7586.c
 
+DRM DRIVER FOR SITRONIX ST7571 PANELS
+M:	Marcus Folkesson <marcus.folkesson@gmail.com>
+S:	Maintained
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+F:	Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
+F:	drivers/gpu/drm/tiny/st7571-i2c.c
+
 DRM DRIVER FOR SITRONIX ST7701 PANELS
 M:	Jagan Teki <jagan@amarulasolutions.com>
 S:	Maintained

-- 
2.48.1

Re: [PATCH 2/3] drm/st7571-i2c: add support for Sitronix ST7571 LCD controller

[Thomas Zimmermann]

Hi,

thanks for the driver. See below for an initial review.

Am 02.04.25 um 08:12 schrieb Marcus Folkesson:
> Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
> The controller has a SPI, I2C and 8bit parallel interface, this
> driver is for the I2C interface only.
>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
> ---
>   drivers/gpu/drm/tiny/Kconfig      |  12 +
>   drivers/gpu/drm/tiny/Makefile     |   1 +
>   drivers/gpu/drm/tiny/st7571-i2c.c | 563 ++++++++++++++++++++++++++++++++++++++
>   3 files changed, 576 insertions(+)
>
> diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
> index 94cbdb1337c07f1628a33599a7130369b9d59d98..14096031e7c2d8f73c06c88e08f35aa5a3790a54 100644
> --- a/drivers/gpu/drm/tiny/Kconfig
> +++ b/drivers/gpu/drm/tiny/Kconfig
> @@ -232,6 +232,18 @@ config TINYDRM_ST7586
>   
>   	  If M is selected the module will be called st7586.
>   
> +config TINYDRM_ST7571_I2C
> +	tristate "DRM support for Sitronix ST7571 display panels (I2C)"
> +	depends on DRM && I2C
> +	select DRM_KMS_HELPER
> +	select DRM_GEM_DMA_HELPER
> +	select DRM_GEM_SHMEM_HELPER

You only need one GEM helper, likely SHMEM in your case.

> +	select REGMAP_I2C
> +	help
> +	  DRM driver for Sitronix ST7571 panels controlled over I2C.
> +
> +	  if M is selected the module will be called st7571-i2c.
> +
>   config TINYDRM_ST7735R
>   	tristate "DRM support for Sitronix ST7715R/ST7735R display panels"
>   	depends on DRM && SPI
> diff --git a/drivers/gpu/drm/tiny/Makefile b/drivers/gpu/drm/tiny/Makefile
> index 60816d2eb4ff93b87228ed8eadd60a0a33a1144b..343813a965e13326bbb8520a5c34d272ec7821d5 100644
> --- a/drivers/gpu/drm/tiny/Makefile
> +++ b/drivers/gpu/drm/tiny/Makefile
> @@ -17,3 +17,4 @@ obj-$(CONFIG_TINYDRM_REPAPER)		+= repaper.o
>   obj-$(CONFIG_TINYDRM_SHARP_MEMORY)	+= sharp-memory.o
>   obj-$(CONFIG_TINYDRM_ST7586)		+= st7586.o
>   obj-$(CONFIG_TINYDRM_ST7735R)		+= st7735r.o
> +obj-$(CONFIG_TINYDRM_ST7571_I2C)	+= st7571-i2c.o

Please keep these entries alphabetically sorted.

> diff --git a/drivers/gpu/drm/tiny/st7571-i2c.c b/drivers/gpu/drm/tiny/st7571-i2c.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..c26ecf8a4fd2115b808b126cccda74ea9079cd7c
> --- /dev/null
> +++ b/drivers/gpu/drm/tiny/st7571-i2c.c
> @@ -0,0 +1,563 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Driver for Sitronix ST7571, a 4 level gray scale dot matrix LCD controller
> + *
> + * Copyright (C) 2025 Marcus Folkesson <marcus.folkesson@gmail.com>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +
> +#include <drm/clients/drm_client_setup.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_connector.h>
> +#include <drm/drm_damage_helper.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_fb_helper.h>
> +#include <drm/drm_fbdev_dma.h>

This should be drm_fbdev_shmem.h.

> +#include <drm/drm_fourcc.h>
> +#include <drm/drm_framebuffer.h>
> +#include <drm/drm_gem_atomic_helper.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
> +#include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_modeset_helper_vtables.h>
> +#include <drm/drm_module.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_simple_kms_helper.h>

Please consider everything in this file as obsolete and don't use it in 
new code.

> +
> +#define ST7571_COMMAND_MODE			(0x00)
> +#define ST7571_DATA_MODE			(0x40)
> +
> +/* Normal mode command set */
> +#define ST7571_DISPLAY_OFF			(0xae)
> +#define ST7571_DISPLAY_ON			(0xaf)
> +#define ST7571_OSC_ON				(0xab)
> +#define ST7571_SET_COLUMN_LSB(c)		(0x00 | ((c) & 0xf))
> +#define ST7571_SET_COLUMN_MSB(c)		(0x10 | ((c) >> 4))
> +#define ST7571_SET_COM0_LSB(x)			((x) & 0x7f)
> +#define ST7571_SET_COM0_MSB			(0x44)
> +#define ST7571_SET_COM_SCAN_DIR(d)		(0xc0 | (((d) << 3) & 0x8))
> +#define ST7571_SET_CONTRAST_LSB(c)		((c) & 0x3f)
> +#define ST7571_SET_CONTRAST_MSB			(0x81)
> +#define ST7571_SET_DISPLAY_DUTY_LSB(d)		((d) & 0xff)
> +#define ST7571_SET_DISPLAY_DUTY_MSB		(0x48)
> +#define ST7571_SET_ENTIRE_DISPLAY_ON(p)		(0xa4 | ((p) & 0x1))
> +#define ST7571_SET_LCD_BIAS(b)			(0x50 | ((b) & 0x7))
> +#define ST7571_SET_MODE_LSB(m)			((m) & 0xfc)
> +#define ST7571_SET_MODE_MSB			(0x38)
> +#define ST7571_SET_PAGE(p)			(0xb0 | (p))
> +#define ST7571_SET_POWER(p)			(0x28 | ((p) & 0x7))
> +#define ST7571_SET_REGULATOR_REG(r)		(0x20 | ((r) & 0x7))
> +#define ST7571_SET_REVERSE(r)			(0xa6 | ((r) & 0x1))
> +#define ST7571_SET_SEG_SCAN_DIR(d)		(0xa0 | ((d) & 0x1))
> +#define ST7571_SET_START_LINE_LSB(l)		((l) & 0x3f)
> +#define ST7571_SET_START_LINE_MSB		(0x40)
> +
> +/* Extension command set 3 */
> +#define ST7571_COMMAND_SET_3			(0x7b)
> +#define ST7571_SET_COLOR_MODE(c)		(0x10 | ((c) & 0x1))
> +#define ST7571_COLOR_MODE_BLACKWHITE		(1)
> +#define ST7571_COLOR_MODE_GRAY			(0)
> +#define ST7571_COMMAND_SET_NORMAL		(0x00)
> +
> +#define DRIVER_NAME "st7571-i2c"
> +#define DRIVER_DESC "ST7571 DRM driver"
> +#define DRIVER_MAJOR 1
> +#define DRIVER_MINOR 0
> +
> +#define to_st7571(_dev) container_of(_dev, struct st7571_device, dev)
> +
> +struct st7571_device {
> +	struct drm_device	       dev;

> +	struct drm_simple_display_pipe pipe;

That structure and its helpers are obsolete. Please open-code its 
content (plane, crtc, encoder) in your driver. Here's an example of how 
this has been done for another driver: 
https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.14&id=72d73dd3a95c7e879c18a0eae8fd2af89b5b3347 
You have to pull all the code and data structures into your driver and 
then streamline your driver to only use regular helpers.


> +	struct drm_connector	       conn;
> +	struct drm_display_mode mode;
> +	struct regmap *regmap;
> +	struct i2c_client *client;
> +	struct gpio_desc *reset;
> +	u8 bpp;
> +	u32 width_mm;
> +	u32 height_mm;
> +	u32 nlines;
> +	u32 startline;
> +	bool ignore_nak;
> +};
> +
> +static int st7571_regmap_write(void *context, const void *data, size_t count)
> +{
> +	struct i2c_client *client = context;
> +	struct st7571_device *st7571 = i2c_get_clientdata(client);
> +	int ret;
> +
> +	struct i2c_msg msg = {
> +		.addr = st7571->client->addr,
> +		.flags = st7571->ignore_nak ? I2C_M_IGNORE_NAK : 0,
> +		.len = count,
> +		.buf = (u8 *)data
> +	};
> +
> +	ret = i2c_transfer(st7571->client->adapter, &msg, 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int st7571_regmap_read(void *context, const void *reg_buf,
> +			       size_t reg_size, void *val_buf, size_t val_size)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static int st7571_send_command_list(struct st7571_device *st7571,
> +				    const u8 *cmd_list, size_t len)
> +{
> +	int ret;
> +
> +	for (int i = 0; i < len; i++) {
> +		ret = regmap_write(st7571->regmap, ST7571_COMMAND_MODE, cmd_list[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +static inline u8 st7571_transform_xy(const char *p, int x, int y)
> +{
> +	int xrest = x % 8;
> +	u8 result = 0;
> +
> +	/*
> +	 * Transforms an (x, y) pixel coordinate into a vertical 8-bit
> +	 * column from the framebuffer. It calculates the corresponding byte in the
> +	 * framebuffer, extracts the bit at the given x position across 8 consecutive
> +	 * rows, and packs those bits into a single byte.
> +	 *
> +	 * Return an 8-bit value representing a vertical column of pixels.
> +	 */
> +	x = x / 8;
> +	y = (y / 8) * 8;
> +
> +	for (int i = 0; i < 8; i++) {
> +		int row_idx = y + i;
> +		u8 byte = p[row_idx * 16 + x];
> +		u8 bit = (byte >> (7-xrest)) & 1;
> +
> +		result |= (bit << i);
> +	}
> +
> +	return result;
> +}
> +
> +static int st7571_set_position(struct st7571_device *st7571, int x, int y)
> +{
> +	u8 cmd_list[] = {
> +		ST7571_SET_COLUMN_LSB(x),
> +		ST7571_SET_COLUMN_MSB(x),
> +		ST7571_SET_PAGE(y/8),
> +	};
> +
> +	return st7571_send_command_list(st7571, cmd_list, ARRAY_SIZE(cmd_list));
> +}
> +
> +static int st7571_fb_blit_rect(struct drm_framebuffer *fb,
> +			       const struct iosys_map *vmap,
> +			       struct drm_rect *rect)
> +{
> +	struct st7571_device *st7571 = to_st7571(fb->dev);
> +
> +	char row[256];
> +	char *pixel = vmap->vaddr;
> +	int x1 = rect->x1 * st7571->bpp;
> +	int x2 = rect->x2 * st7571->bpp;
> +
> +	for (int y = rect->y1; y < rect->y2; y += 8) {
> +		for (int x = x1; x < x2; x++)
> +			row[x] = st7571_transform_xy(pixel, x, y);
> +
> +		st7571_set_position(st7571, rect->x1, y);
> +
> +		/* TODO: Investige why we can't write multiple bytes at once */
> +		for (int x = x1; x < x2; x++)
> +			regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);
> +	}
> +
> +	return 0;
> +}
> +
> +static int st7571_fb_blit_fullscreen(struct drm_framebuffer *fb,
> +				     const struct iosys_map *map)
> +{
> +	struct drm_rect fullscreen = {
> +		.x1 = 0,
> +		.x2 = fb->width,
> +		.y1 = 0,
> +		.y2 = fb->height,
> +	};
> +
> +	return st7571_fb_blit_rect(fb, map, &fullscreen);
> +}
> +
> +static int st7571_conn_get_modes(struct drm_connector *conn)
> +{
> +	struct st7571_device *st7571 = to_st7571(conn->dev);
> +
> +	return drm_connector_helper_get_modes_fixed(conn, &st7571->mode);
> +}
> +
> +static const struct drm_connector_helper_funcs st7571_conn_helper_funcs = {
> +	.get_modes = st7571_conn_get_modes,
> +};
> +
> +static const struct drm_connector_funcs st7571_conn_funcs = {
> +	.fill_modes = drm_helper_probe_single_connector_modes,
> +	.destroy = drm_connector_cleanup,
> +	.reset = drm_atomic_helper_connector_reset,
> +	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +};
> +
> +static int st7571_conn_init(struct st7571_device *st7571)
> +{
> +	drm_connector_helper_add(&st7571->conn, &st7571_conn_helper_funcs);
> +	return drm_connector_init(&st7571->dev, &st7571->conn,
> +				  &st7571_conn_funcs, DRM_MODE_CONNECTOR_Unknown);
> +
> +}
> +
> +
> +static void st7571_pipe_enable(struct drm_simple_display_pipe *pipe,
> +			       struct drm_crtc_state *crtc_state,
> +			       struct drm_plane_state *plane_state)
> +{
> +	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
> +
> +	st7571_fb_blit_fullscreen(plane_state->fb, &shadow_plane_state->data[0]);
> +}
> +
> +static void st7571_pipe_update(struct drm_simple_display_pipe *pipe,
> +			       struct drm_plane_state *old_state)
> +{
> +	struct drm_plane_state *state = pipe->plane.state;
> +	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
> +	struct drm_rect rect;
> +
> +	if (state->fb && drm_atomic_helper_damage_merged(old_state, state, &rect))
> +		st7571_fb_blit_rect(state->fb, &shadow_plane_state->data[0], &rect);
> +}
> +
> +static const struct drm_simple_display_pipe_funcs st7571_pipe_funcs = {
> +	.enable	    = st7571_pipe_enable,
> +	.update	    = st7571_pipe_update,
> +	DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
> +};
> +
> +static const uint32_t st7571_formats[] = {
> +	DRM_FORMAT_C1,
> +	DRM_FORMAT_C2,
> +};
> +
> +static const uint64_t st7571_modifiers[] = {
> +	DRM_FORMAT_MOD_LINEAR,
> +	DRM_FORMAT_MOD_INVALID
> +};
> +
> +static int st7571_pipe_init(struct st7571_device *st7571)
> +{
> +	return drm_simple_display_pipe_init(&st7571->dev,
> +					    &st7571->pipe,
> +					    &st7571_pipe_funcs,
> +					    st7571_formats,
> +					    ARRAY_SIZE(st7571_formats),
> +					    st7571_modifiers,
> +					    &st7571->conn);
> +}
> +
> +static int st7571_set_pixel_format(struct st7571_device *st7571,
> +				   u32 pixel_format)
> +{
> +	u8 cmd_list[] = {
> +		ST7571_COMMAND_SET_3,
> +		ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_BLACKWHITE),
> +		ST7571_COMMAND_SET_NORMAL,
> +	};
> +
> +	switch (pixel_format) {
> +	case DRM_FORMAT_C1:
> +		cmd_list[1] = ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_BLACKWHITE);
> +		st7571->bpp = 1;
> +		break;
> +	case DRM_FORMAT_C2:
> +		cmd_list[1] = ST7571_SET_COLOR_MODE(ST7571_COLOR_MODE_GRAY);
> +		st7571->bpp = 2;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return st7571_send_command_list(st7571, cmd_list, ARRAY_SIZE(cmd_list));
> +}
> +
> +static struct drm_framebuffer*
> +st7571_fb_create(struct drm_device *dev, struct drm_file *file_priv,
> +		 const struct drm_mode_fb_cmd2 *mode_cmd)
> +{
> +	int ret = st7571_set_pixel_format(to_st7571(dev), mode_cmd->pixel_format);

You need to set the pixel format in the primary plane's atomic_update. 
The function here only allocates the graphics buffer.

> +
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return drm_gem_fb_create_with_dirty(dev, file_priv, mode_cmd);
> +}
> +
> +static const struct drm_mode_config_funcs st7571_mode_config_funcs = {
> +	.fb_create = st7571_fb_create,
> +	.atomic_check = drm_atomic_helper_check,
> +	.atomic_commit = drm_atomic_helper_commit,
> +};
> +
> +static int st7571_mode_config_init(struct st7571_device *st7571)
> +{
> +	struct drm_device *dev = &st7571->dev;
> +	int ret;
> +
> +	ret = drmm_mode_config_init(dev);
> +	if (ret)
> +		return ret;
> +
> +	dev->mode_config.min_width = 0;
> +	dev->mode_config.min_height = 0;
> +	dev->mode_config.max_width = 128;
> +	dev->mode_config.max_height = 128;
> +	dev->mode_config.preferred_depth = 1;
> +	dev->mode_config.prefer_shadow = 0;
> +	dev->mode_config.funcs = &st7571_mode_config_funcs;
> +
> +	return 0;
> +}
> +
> +DEFINE_DRM_GEM_FOPS(st7571_fops);
> +
> +static const struct drm_driver st7571_driver = {
> +	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
> +
> +	.name		 = DRIVER_NAME,
> +	.desc		 = DRIVER_DESC,
> +	.major		 = DRIVER_MAJOR,
> +	.minor		 = DRIVER_MINOR,
> +
> +	.fops		 = &st7571_fops,
> +	DRM_GEM_SHMEM_DRIVER_OPS,

> +	DRM_FBDEV_DMA_DRIVER_OPS,

Needs to be DRM_FBDEV_SHMEM_DRIVER_OPS.

There's more review to do, but the required rework will already change 
the driver significantly.

Best regards
Thomas


> +};
> +
> +static const struct regmap_bus st7571_regmap_bus = {
> +	.read = st7571_regmap_read,
> +	.write = st7571_regmap_write,
> +};
> +
> +static const struct regmap_config st7571_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.use_single_write = true,
> +};
> +
> +static int st7571_parse_dt(struct st7571_device *st7571)
> +{
> +	struct device *dev = &st7571->client->dev;
> +	struct device_node *np = dev->of_node;
> +
> +	of_property_read_u32(np, "sitronix,panel-width-mm", &st7571->width_mm);
> +	of_property_read_u32(np, "sitronix,panel-height-mm", &st7571->height_mm);
> +	of_property_read_u32(np, "sitronix,panel-start-line", &st7571->startline);
> +	of_property_read_u32(np, "sitronix,panel-nlines", &st7571->nlines);
> +
> +	if (st7571->width_mm == 0 || st7571->height_mm == 0) {
> +		dev_err(dev, "Invalid panel dimensions\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Default to 128 lines if not specified */
> +	if (!st7571->nlines)
> +		st7571->nlines = 128;
> +
> +	if (st7571->startline + st7571->nlines > 128) {
> +		dev_err(dev, "Invalid line configuration (start-line=%i, nlines=%i)\n",
> +			st7571->startline, st7571->nlines);
> +		return -EINVAL;
> +	}
> +
> +	st7571->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(st7571->reset))
> +		return PTR_ERR(st7571->reset);
> +
> +	return 0;
> +}
> +
> +static void st7571_create_mode(struct st7571_device *st7571)
> +{
> +	struct drm_display_mode st7571_mode = {
> +		DRM_SIMPLE_MODE(128, st7571->nlines, st7571->width_mm, st7571->height_mm),
> +	};
> +
> +	memcpy(&st7571->mode, &st7571_mode, sizeof(st7571_mode));
> +}
> +
> +static void st7571_reset(struct st7571_device *st7571)
> +{
> +	gpiod_set_value_cansleep(st7571->reset, 0);
> +	mdelay(20);
> +	gpiod_set_value_cansleep(st7571->reset, 1);
> +}
> +
> +static int st7571_initialize(struct st7571_device *st7571)
> +{
> +	/*
> +	 * Most of the initialization sequence is taken directly from the
> +	 * referential initial code in the ST7571 datasheet.
> +	 */
> +	u8 commands[] = {
> +		ST7571_DISPLAY_OFF,
> +		ST7571_SET_MODE_MSB,
> +
> +		ST7571_SET_MODE_LSB(0x94),
> +		ST7571_SET_SEG_SCAN_DIR(0),
> +		ST7571_SET_COM_SCAN_DIR(1),
> +
> +		ST7571_SET_COM0_MSB,
> +		ST7571_SET_COM0_LSB(0x00),
> +
> +		ST7571_SET_START_LINE_MSB,
> +		ST7571_SET_START_LINE_LSB(st7571->startline),
> +
> +		ST7571_OSC_ON,
> +		ST7571_SET_REGULATOR_REG(5),
> +		ST7571_SET_CONTRAST_MSB,
> +		ST7571_SET_CONTRAST_LSB(0x33),
> +		ST7571_SET_LCD_BIAS(0x04),
> +		ST7571_SET_DISPLAY_DUTY_MSB,
> +		ST7571_SET_DISPLAY_DUTY_LSB(st7571->nlines),
> +
> +
> +		ST7571_SET_POWER(0x4),	/* Power Control, VC: ON, VR: OFF, VF: OFF */
> +		ST7571_SET_POWER(0x6),	/* Power Control, VC: ON, VR: ON, VF: OFF */
> +		ST7571_SET_POWER(0x7),	/* Power Control, VC: ON, VR: ON, VF: ON */
> +
> +		ST7571_SET_REVERSE(0),
> +		ST7571_SET_ENTIRE_DISPLAY_ON(0),
> +
> +		ST7571_DISPLAY_ON,
> +	};
> +
> +	/* Perform a reset before initializing the controller */
> +	st7571_reset(st7571);
> +
> +	return st7571_send_command_list(st7571, commands, ARRAY_SIZE(commands));
> +}
> +
> +
> +static int st7571_probe(struct i2c_client *client)
> +{
> +	struct drm_device *dev;
> +	struct st7571_device *st7571;
> +	int ret;
> +
> +	st7571 = devm_drm_dev_alloc(&client->dev, &st7571_driver,
> +				    struct st7571_device, dev);
> +	if (IS_ERR(st7571))
> +		return PTR_ERR(st7571);
> +
> +	dev = &st7571->dev;
> +	st7571->client = client;
> +	i2c_set_clientdata(client, st7571);
> +
> +	ret = st7571_parse_dt(st7571);
> +	if (ret)
> +		return ret;
> +
> +	/* Create mode with parsed values */
> +	st7571_create_mode(st7571);
> +
> +	/*
> +	 * The chip nacks some messages but still works as expected.
> +	 * If the adapter does not support protocol mangling do
> +	 * not set the I2C_M_IGNORE_NAK flag at the expense * of possible
> +	 * cruft in the logs.
> +	 */
> +	if (i2c_check_functionality(client->adapter, I2C_FUNC_PROTOCOL_MANGLING))
> +		st7571->ignore_nak = true;
> +
> +	st7571->regmap = devm_regmap_init(&client->dev, &st7571_regmap_bus,
> +					   client, &st7571_regmap_config);
> +	if (IS_ERR(st7571->regmap)) {
> +		dev_err(&client->dev, "Failed to initialize regmap\n");
> +		return PTR_ERR(st7571->regmap);
> +	}
> +
> +	ret = st7571_initialize(st7571);
> +	if (ret)
> +		return ret;
> +
> +	ret = st7571_mode_config_init(st7571);
> +	if (ret)
> +		return ret;
> +
> +	ret = st7571_conn_init(st7571);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = st7571_pipe_init(st7571);
> +	if (ret < 0)
> +		return ret;
> +
> +	drm_plane_enable_fb_damage_clips(&st7571->pipe.plane);
> +	drm_mode_config_reset(dev);
> +
> +	ret = drm_dev_register(dev, 0);
> +	if (ret)
> +		return ret;
> +
> +	drm_client_setup(dev, NULL);
> +	return 0;
> +}
> +
> +static void st7571_remove(struct i2c_client *client)
> +{
> +	struct st7571_device *st7571 = i2c_get_clientdata(client);
> +
> +	drm_dev_unplug(&st7571->dev);
> +	drm_atomic_helper_shutdown(&st7571->dev);
> +}
> +
> +static const struct of_device_id st7571_of_match[] = {
> +	{ .compatible = "sitronix,st7571-i2c" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, st7571_of_match);
> +
> +
> +static const struct i2c_device_id st7571_id[] = {
> +	{ "st7571-i2c", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, st7571_id);
> +
> +static struct i2c_driver st7571_i2c_driver = {
> +	.driver = {
> +		.name = "st7571-i2c",
> +		.of_match_table = st7571_of_match,
> +	},
> +	.probe = st7571_probe,
> +	.remove = st7571_remove,
> +	.id_table = st7571_id,
> +};
> +
> +module_i2c_driver(st7571_i2c_driver);
> +
> +MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
> +MODULE_DESCRIPTION("DRM Driver for Sitronix ST7571 LCD controller");
> +MODULE_LICENSE("GPL");
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Krzysztof Kozlowski]

On Wed, Apr 02, 2025 at 08:12:10AM +0200, Marcus Folkesson wrote:
> Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
> The controller has a SPI, I2C and 8bit parallel interface, this is for
> the I2C interface only.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
> ---
>  .../bindings/display/sitronix,st7571-i2c.yaml      | 71 ++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..6e5e0994a98db646a37bb17c4289332546c9266e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml

Drop i2c

> @@ -0,0 +1,71 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/sitronix,st7571-i2c.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Sitronix ST7571 Display Panels
> +
> +maintainers:
> +  - Marcus Folkesson <marcus.folkesson@gmail.com>
> +
> +properties:
> +  compatible:
> +    const: sitronix,st7571-i2c

Drop i2c

> +
> +  reg:
> +    description: I2C address of the LCD controller

Drop description


> +    maxItems: 1
> +
> +  sitronix,panel-width-mm:
> +    description: physical panel width [mm]
> +
> +  sitronix,panel-height-mm:
> +    description: physical panel height [mm]

No, use standard properties.

> +
> +  sitronix,panel-nlines:
> +    description: Number of lines in the panel
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 1
> +    maximum: 128
> +    default: 128

Ditto

> +
> +  sitronix,panel-start-line:
> +    description: Start line of the panel
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 127
> +    default: 0

Ditto

> +
> +  reset-gpios:
> +    description: GPIO connected to the RST_N signal.
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - reset-gpios

Keep same order as in properties.

> +  - sitronix,panel-width-mm
> +  - sitronix,panel-height-mm
> +

Missing ref to panels schema.

> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #

Drop

> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        display@3f {

Look how this is called in other bindings... The binding and example are
not following existing code. Why? Why doing something entirely
different?

Best regards,
Krzysztof

Re: [PATCH 3/3] MAINTAINERS: add antry for Sitronix ST7571 LCD controller

[Krzysztof Kozlowski]

On Wed, Apr 02, 2025 at 08:12:12AM +0200, Marcus Folkesson wrote:
> Add MAINTAINERS entry for the Sitronix ST7571 dot matrix LCD
> controller.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
> ---
>  MAINTAINERS | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 889bd4a59551c9bc125f94944a6e1c7e3ef2de83..00d19d45679f6d18a7e9c9e619b7642176b7ef95 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7572,6 +7572,13 @@ T:	git https://gitlab.freedesktop.org/drm/misc/kernel.git
>  F:	Documentation/devicetree/bindings/display/sitronix,st7586.txt
>  F:	drivers/gpu/drm/tiny/st7586.c
>  
> +DRM DRIVER FOR SITRONIX ST7571 PANELS
> +M:	Marcus Folkesson <marcus.folkesson@gmail.com>
> +S:	Maintained
> +T:	git git://anongit.freedesktop.org/drm/drm-misc

Are you one of the maintainers and do you actually push there? If not,
drop.

Best regards,
Krzysztof

Re: [PATCH 2/3] drm/st7571-i2c: add support for Sitronix ST7571 LCD controller

[Krzysztof Kozlowski]

On Wed, Apr 02, 2025 at 08:12:11AM +0200, Marcus Folkesson wrote:
> +
> +static void st7571_reset(struct st7571_device *st7571)
> +{
> +	gpiod_set_value_cansleep(st7571->reset, 0);
> +	mdelay(20);
> +	gpiod_set_value_cansleep(st7571->reset, 1);

huh? Why do you keep reset ACTIVE after performing reset? This makes no
sense, unless you just put wrong flags into your DTS. Your binding
already suggest that - you claim this is N signal, but use high flag.

> +}
> +
> +static int st7571_initialize(struct st7571_device *st7571)
> +{
> +	/*
> +	 * Most of the initialization sequence is taken directly from the
> +	 * referential initial code in the ST7571 datasheet.

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Krzysztof Kozlowski]

On Wed, Apr 02, 2025 at 08:12:10AM +0200, Marcus Folkesson wrote:
> +        display@3f {
> +          compatible = "sitronix,st7571-i2c";
> +          reg = <0x3f>;
> +
> +          reset-gpios = <&gpio0 3 GPIO_ACTIVE_HIGH>;


so RST or RST_N?

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Krzysztof Kozlowski]

On 02/04/2025 08:12, Marcus Folkesson wrote:
> Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
> The controller has a SPI, I2C and 8bit parallel interface, this is for
> the I2C interface only.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
I spotted one more thing:

Please use subject prefixes matching the subsystem. You can get them for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching. For bindings, the preferred subjects are
explained here:
https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters

(missing display parts)

A nit, subject: drop second/last, redundant "bindings". The
"dt-bindings" prefix is already stating that these are bindings.
See also:
https://elixir.bootlin.com/linux/v6.7-rc8/source/Documentation/devicetree/bindings/submitting-patches.rst#L18

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Marcus Folkesson]

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Thank you Krzysztof,

I will fix the issues you pointed out, just a few comments below.

On Wed, Apr 02, 2025 at 10:27:53AM +0200, Krzysztof Kozlowski wrote:
> On Wed, Apr 02, 2025 at 08:12:10AM +0200, Marcus Folkesson wrote:
> > Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
> > The controller has a SPI, I2C and 8bit parallel interface, this is for
> > the I2C interface only.
> > 
> > Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
> > ---
> >  .../bindings/display/sitronix,st7571-i2c.yaml      | 71 ++++++++++++++++++++++
> >  1 file changed, 71 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..6e5e0994a98db646a37bb17c4289332546c9266e
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/sitronix,st7571-i2c.yaml
> 

[...]

> 
> > +    maxItems: 1
> > +
> > +  sitronix,panel-width-mm:
> > +    description: physical panel width [mm]
> > +
> > +  sitronix,panel-height-mm:
> > +    description: physical panel height [mm]
> 
> No, use standard properties.

I will use width-mm and height-mm from panels.yaml from
panel-common.yaml instead

> 
> > +
> > +  sitronix,panel-nlines:
> > +    description: Number of lines in the panel
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    minimum: 1
> > +    maximum: 128
> > +    default: 128
> 
> Ditto

I will use vactive in panel-timing instead.

Do I need to specify those properties or should I just list them as
required?

Some bindings set e.g.

reg: true
reset-gpios: true

and others just list them as required.


> 
> > +
> > +  sitronix,panel-start-line:
> > +    description: Start line of the panel
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    minimum: 0
> > +    maximum: 127
> > +    default: 0
> 
> Ditto

I will use vfront-porch in panel-timing instead.


[...]
> 
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        display@3f {
> 
> Look how this is called in other bindings... The binding and example are
> not following existing code. Why? Why doing something entirely
> different?

Sorry, I'm not sure what you mean here.

> 
> Best regards,
> Krzysztof

Best regards,
Marcus Folkesson

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Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Krzysztof Kozlowski]

On 03/04/2025 12:31, Marcus Folkesson wrote:
>>> +    i2c {
>>> +        #address-cells = <1>;
>>> +        #size-cells = <0>;
>>> +
>>> +        display@3f {
>>
>> Look how this is called in other bindings... The binding and example are
>> not following existing code. Why? Why doing something entirely
>> different?
> 
> Sorry, I'm not sure what you mean here.
You added code entirely different than existing code. Why doing
something entirely different? Open any other panel and look how it is
called.

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: st7571-i2c: Add Sitronix ST7571 panel bindings

[Marcus Folkesson]

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On Thu, Apr 03, 2025 at 04:28:22PM +0200, Krzysztof Kozlowski wrote:
> On 03/04/2025 12:31, Marcus Folkesson wrote:
> >>> +    i2c {
> >>> +        #address-cells = <1>;
> >>> +        #size-cells = <0>;
> >>> +
> >>> +        display@3f {
> >>
> >> Look how this is called in other bindings... The binding and example are
> >> not following existing code. Why? Why doing something entirely
> >> different?
> > 
> > Sorry, I'm not sure what you mean here.
> You added code entirely different than existing code. Why doing
> something entirely different? Open any other panel and look how it is
> called.

This is still unclear to me.

I assume you are referring to the display@3f?
I can see many other panels use display@<address>, e.g.
elgin,jg10309-01.yaml
and 
sitronix,st7735r.yaml

Those are using address 0, but that is because they are SPI devices,
this is a I2C device and address 0 is not valid. 
There are plenty of examples of I2C devices using the real addresses in the
node name.

Or do you want me to call it panel@3f ?
I can go with that if it is preferred.

> 
> Best regards,
> Krzysztof

Best regards,
Marcus Folkesson

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