drm/sitronix/st7571-i2c: Add support for the ST7567 Controller

The Sitronix ST7567 is a monochrome Dot Matrix LCD Controller that has SPI,
I2C and parallel interfaces. The st7571-i2c driver only has support for I2C
so displays using other transport interfaces are currently not supported.

The DRM_FORMAT_R1 pixel format and data commands are the same than what
is used by the ST7571 controller, so only is needed a different callback
that implements the expected initialization sequence for the ST7567 chip.

Reviewed-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250715110411.448343-6-javierm@redhat.com
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sitronix/st7571-i2c.c b/drivers/gpu/drm/sitronix/st7571-i2c.c
index f9c4fedb3cca..453eb7e045e5 100644
--- a/drivers/gpu/drm/sitronix/st7571-i2c.c
+++ b/drivers/gpu/drm/sitronix/st7571-i2c.c
@@ -68,6 +68,9 @@
 #define ST7571_SET_COLOR_MODE(c)		(0x10 | FIELD_PREP(GENMASK(0, 0), (c)))
 #define ST7571_COMMAND_SET_NORMAL		(0x00)
 
+/* ST7567 commands */
+#define ST7567_SET_LCD_BIAS(m) (0xa2 | FIELD_PREP(GENMASK(0, 0), (m)))
+
 #define ST7571_PAGE_HEIGHT 8
 
 #define DRIVER_NAME "st7571"
@@ -774,6 +777,32 @@ static int st7571_validate_parameters(struct st7571_device *st7571)
 	return 0;
 }
 
+static int st7567_parse_dt(struct st7571_device *st7567)
+{
+	struct device *dev = &st7567->client->dev;
+	struct device_node *np = dev->of_node;
+	struct display_timing dt;
+	int ret;
+
+	ret = of_get_display_timing(np, "panel-timing", &dt);
+	if (ret) {
+		dev_err(dev, "Failed to get display timing from DT\n");
+		return ret;
+	}
+
+	of_property_read_u32(np, "width-mm", &st7567->width_mm);
+	of_property_read_u32(np, "height-mm", &st7567->height_mm);
+
+	st7567->pformat = &st7571_monochrome;
+	st7567->bpp = 1;
+
+	st7567->startline = dt.vfront_porch.typ;
+	st7567->nlines = dt.vactive.typ;
+	st7567->ncols = dt.hactive.typ;
+
+	return 0;
+}
+
 static int st7571_parse_dt(struct st7571_device *st7571)
 {
 	struct device *dev = &st7571->client->dev;
@@ -819,6 +848,38 @@ static void st7571_reset(struct st7571_device *st7571)
 	gpiod_set_value_cansleep(st7571->reset, 0);
 }
 
+static int st7567_lcd_init(struct st7571_device *st7567)
+{
+	/*
+	 * Most of the initialization sequence is taken directly from the
+	 * referential initial code in the ST7567 datasheet.
+	 */
+	u8 commands[] = {
+		ST7571_DISPLAY_OFF,
+
+		ST7567_SET_LCD_BIAS(1),
+
+		ST7571_SET_SEG_SCAN_DIR(0),
+		ST7571_SET_COM_SCAN_DIR(1),
+
+		ST7571_SET_REGULATOR_REG(4),
+		ST7571_SET_CONTRAST_MSB,
+		ST7571_SET_CONTRAST_LSB(0x20),
+
+		ST7571_SET_START_LINE_MSB,
+		ST7571_SET_START_LINE_LSB(st7567->startline),
+
+		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),
+	};
+
+	return st7571_send_command_list(st7567, commands, ARRAY_SIZE(commands));
+}
+
 static int st7571_lcd_init(struct st7571_device *st7571)
 {
 	/*
@@ -963,6 +1024,18 @@ static void st7571_remove(struct i2c_client *client)
 	drm_dev_unplug(&st7571->dev);
 }
 
+struct st7571_panel_data st7567_config = {
+	.init = st7567_lcd_init,
+	.parse_dt = st7567_parse_dt,
+	.constraints = {
+		.min_nlines = 1,
+		.max_nlines = 64,
+		.min_ncols = 128,
+		.max_ncols = 128,
+		.support_grayscale = false,
+	},
+};
+
 struct st7571_panel_data st7571_config = {
 	.init = st7571_lcd_init,
 	.parse_dt = st7571_parse_dt,
@@ -976,12 +1049,14 @@ struct st7571_panel_data st7571_config = {
 };
 
 static const struct of_device_id st7571_of_match[] = {
+	{ .compatible = "sitronix,st7567", .data = &st7567_config },
 	{ .compatible = "sitronix,st7571", .data = &st7571_config },
 	{},
 };
 MODULE_DEVICE_TABLE(of, st7571_of_match);
 
 static const struct i2c_device_id st7571_id[] = {
+	{ "st7567", 0 },
 	{ "st7571", 0 },
 	{ }
 };