drivers: display: ssd16xx: enable SSD1680 RAM ping-pong

SSD1680 supports RAM ping-pong for display mode 2 through the display
option register. Enable F[6] when switching to the partial refresh
profile so partial updates can use the controller's buffer swap behavior.

Expose this as a "ram-ping-pong-mode2" devicetree property on the
SSD1680-specific binding.

Signed-off-by: Aleksandrs Sevastjanovs <sevalks@gmail.com>

Author: skandinaff

drivers/display/ssd16xx.c

@@ -17,6 +17,7 @@ LOG_MODULE_REGISTER(ssd16xx);
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/drivers/mipi_dbi.h>
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/util.h>
 
 #include <zephyr/display/ssd16xx.h>
 #include "ssd16xx_regs.h"
@@ -31,6 +32,9 @@ LOG_MODULE_REGISTER(ssd16xx);
 #define SSD16XX_PIXELS_PER_BYTE		8
 #define SSD16XX_DEFAULT_TR_VALUE	25U
 #define SSD16XX_TR_SCALE_FACTOR		256U
+#define SSD16XX_DISPLAY_OPTION_LEN	10U
+#define SSD16XX_DISPLAY_OPTION_F	5U
+#define SSD16XX_DISPLAY_OPTION_RAM_PINGPONG	BIT(6)
 
 
 enum ssd16xx_profile_type {
@@ -104,6 +108,7 @@ struct ssd16xx_config {
 	uint16_t rotation;
 	uint16_t height;
 	uint16_t width;
+	bool ram_ping_pong_mode2;
 	uint8_t tssv;
 };
 
@@ -732,6 +737,18 @@ static int ssd16xx_load_lut(const struct device *dev,
 	}
 }
 
+static int ssd16xx_enable_ram_pingpong(const struct device *dev)
+{
+	uint8_t display_option[SSD16XX_DISPLAY_OPTION_LEN] = { 0 };
+
+	/* F[6] enables RAM ping-pong for display mode 2. */
+	display_option[SSD16XX_DISPLAY_OPTION_F] =
+		SSD16XX_DISPLAY_OPTION_RAM_PINGPONG;
+
+	return ssd16xx_write_cmd(dev, SSD16XX_CMD_OTP_SELECTION_CTRL,
+				      display_option, sizeof(display_option));
+}
+
 static int ssd16xx_set_profile(const struct device *dev,
 			       enum ssd16xx_profile_type type)
 {
@@ -843,6 +860,13 @@ static int ssd16xx_set_profile(const struct device *dev,
 		}
 	}
 
+	if (type == SSD16XX_PROFILE_PARTIAL && config->ram_ping_pong_mode2) {
+		err = ssd16xx_enable_ram_pingpong(dev);
+		if (err < 0) {
+			return err;
+		}
+	}
+
 	err = ssd16xx_write_uint8(dev, SSD16XX_CMD_ENTRY_MODE, data->scan_mode);
 	if (err < 0) {
 		return err;
@@ -1071,6 +1095,7 @@ static struct ssd16xx_quirks quirks_solomon_ssd1681 = {
 		.quirks = quirks_ptr,					\
 		.height = DT_PROP(n, height),				\
 		.width = DT_PROP(n, width),				\
+		.ram_ping_pong_mode2 = DT_PROP_OR(n, ram_ping_pong_mode2, false),	\
 		.rotation = DT_PROP(n, rotation),			\
 		.tssv = DT_PROP_OR(n, tssv, 0),				\
 		.softstart = SSD16XX_ASSIGN_ARRAY(n, softstart),	\

dts/bindings/display/solomon,ssd1680.yaml

@@ -6,3 +6,10 @@ description: Solomon Systech SSD1680 296x176 EPD display controller
 compatible: "solomon,ssd1680"
 
 include: solomon,ssd16xx-common.yaml
+
+properties:
+  ram-ping-pong-mode2:
+    type: boolean
+    description:
+      Enable RAM ping-pong for display mode 2 by setting F[6] in the
+      display option register.

tests/drivers/build_all/display/app.overlay

@@ -115,6 +115,7 @@
 				width = <250>;
 				height = <122>;
 				busy-gpios = <&test_gpio 0 0>;
+				ram-ping-pong-mode2;
 			};
 
 			test_uc8176_waveshare_epaper_gdew042t2: uc8176@5 {