boards: shields: add st_b_dsi_mb1314 shield (DSI display)

Addition of a new shield which embeds a round DSI display
gvo,g1120tb101 of 390x390 pixels, with a touchpanel.
This shield enables it via usage of the LTDC and DSI
of the STM32.

Touchpanel isn't yet supported in this commit and will
be added later on in an additional commit.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>

Author: Alain Volmat

boards/shields/st_b_dsi_mb1314/Kconfig.shield

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+# Copyright (c) 2025 STMicroelectronics
+
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_ST_B_DSI_MB1314
+	def_bool $(shields_list_contains,st_b_dsi_mb1314)

boards/shields/st_b_dsi_mb1314/boards/stm32l4r9i_disco.conf

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+CONFIG_DISPLAY=y
+CONFIG_MIPI_DSI=y
+CONFIG_STM32_LTDC_RGB565=y
+CONFIG_STM32_LTDC_FB_NUM=1
+CONFIG_GPIO_HOGS_INIT_PRIORITY=71

boards/shields/st_b_dsi_mb1314/boards/stm32l4r9i_disco.overlay

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+/*
+ * Copyright (c) 2025 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&clk_hse {
+	clock-frequency = <DT_FREQ_M(16)>; /* 16MHz */
+	status = "okay";
+};
+
+&ltdc {
+	/* SRAM0 is too small to hold a framebuffer, use SRAM2 */
+	ext-sdram = <&sram2>;
+};
+
+&mfx {
+	dsi_3v3_pwron {
+		gpio-hog;
+		gpios = <8 GPIO_ACTIVE_LOW>;
+		output-high;
+		line-name = "DSI_3V3_PWRON";
+	};
+
+	dsi_1v8_pwron {
+		gpio-hog;
+		gpios = <18 GPIO_ACTIVE_HIGH>;
+		output-high;
+		line-name = "DSI_1v8_PWRON";
+	};
+};
+
+&pllsai2 {
+	/* PLLSAI2 is here to generate the PCLK to feed the DSI
+	 * We need to feed roughly 500Mbps. PCLK depends on format
+	 * For 24bit (RGB888) format, we need roughly 20.8 MHz.  (Actually target 15 MHz)
+	 *   div-m = 1, mul-n = 60, div-r = 4, div-divr = 4
+	 *
+	 * PCLK = MSI (4MHz) * mul-n / (div-m * div-r * div-divr)
+	 */
+	status = "okay";
+	div-m = <1>;
+	mul-n = <60>;
+	div-r = <4>;
+	div-divr = <4>;
+	clocks = <&clk_msi>;
+};

boards/shields/st_b_dsi_mb1314/doc/index.rst

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+.. _st_b_dsi_mb1314:
+
+ST B-DSI-MB1314
+###############
+
+Overview
+********
+
+This shield provides a DSI display, based on a round AMOLED touch-sensitive panel
+of 1.2 inches and 390x390 pixels. The display module reference is IEG1120TB103GF-001
+from Govisionox Optoelectronics. It displays up to 16M colors.
+
+.. figure:: mb1314.webp
+   :alt: B-DSI-MB1314 Image
+   :align: center
+
+   B-DSI-MB1314 Image
+
+Requirements
+************
+
+Your board needs to have ``zephyr_mipi_dsi`` and ``zephyr_lcd_controller``
+device-tree labels to work with this shield.
+
+Usage
+*****
+
+The shield can be used in any application by setting ``SHIELD`` to
+``st_b_dsi_mb1314`` and adding the necessary board specific device tree
+properties.
+
+Set ``--shield "st_b_dsi_mb1314"`` when you invoke ``west build``. For example:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/drivers/display
+   :board: stm32l4r9i_disco
+   :shield: st_b_dsi_mb1314
+   :goals: build
+
+References
+**********
+
+- `Product page <https://www.st.com/en/evaluation-tools/32l4r9idiscovery.html>`_
+
+- `User manual <https://www.st.com/resource/en/user_manual/um2271-discovery-kit-with-stm32l4r9ai-mcu-stmicroelectronics.pdf>`_

boards/shields/st_b_dsi_mb1314/doc/mb1314.webp

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+shield:
+  name: st_b_dsi_mb1314
+  full_name: ST B-DSI-MB1314
+  vendor: st
+  supported_features:
+    - display

boards/shields/st_b_dsi_mb1314/shield.yml

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+/*
+ * Copyright (c) 2025 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/dt-bindings/mipi_dsi/mipi_dsi.h>
+
+/ {
+	chosen {
+		zephyr,display = &zephyr_lcd_controller;
+	};
+};
+
+&zephyr_mipi_dsi {
+	status = "okay";
+
+	/* DSI HOST dedicated PLL to generate 62.5 MHz from 16MHz
+	 * source clock, in order to generate 500Mbps on single lane
+	 *
+	 * F_VCO = CLK_IN / pll-idf * 2 * pll-ndiv
+	 * PHI = F_VCO / 2 / (1 << pll-odf) = lane_byte_clk
+	 *     = 25 MHz / 5 * 2 * 100 / 2 / (1<<0) / 8 = 62.5 MHz
+	 */
+	pll-ndiv = <125>;
+	pll-idf = <4>;
+	pll-odf = <0>;
+
+	phy-timings = <33 /* ClockLaneHS2LPTime */
+		       30 /* ClockLaneLP2HSTime */
+		       11 /* DataLaneHS2LPTime */
+		       21 /* DataLaneLP2HSTime */
+		       0 /* DataLaneMaxReadTime */
+		       7 /* StopWaitTime */>;
+
+	host-timeouts = <1 /* TimeoutCkdiv */
+			 0 /* HighSpeedTransmissionTimeout */
+			 0 /* LowPowerReceptionTimeout */
+			 0 /* HighSpeedReadTimeout */
+			 0 /* LowPowerReadTimeout */
+			 0 /* HighSpeedWriteTimeout */
+			 0 /* HighSpeedWritePrespMode */
+			 0 /* LowPowerWriteTimeout */
+			 0 /* BTATimeout */>;
+
+	vs-active-high;
+	hs-active-high;
+	de-active-high;
+
+	lp-rx-filter=<10000>;
+
+	g1120tb101: panel@0 {
+		compatible = "gvo,g1120tb101";
+		reg = <0x0>;
+		height = <390>;
+		width = <390>;
+		data-lanes = <1>;
+		reset-gpios = <&dsi_lcd_qsh_030 57 GPIO_ACTIVE_LOW>;
+
+		pixel-format = <MIPI_DSI_PIXFMT_RGB888>;
+	};
+};
+
+&zephyr_lcd_controller {
+	status = "okay";
+
+	width = <390>;
+	height = <390>;
+	pixel-format = <PANEL_PIXEL_FORMAT_RGB_888>;
+
+	display-timings {
+		compatible = "zephyr,panel-timing";
+		de-active = <0>;
+		pixelclk-active = <0>;
+		hsync-active = <0>;
+		vsync-active = <0>;
+		hsync-len = <1>;
+		vsync-len = <1>;
+		hback-porch = <1>;
+		vback-porch = <1>;
+		hfront-porch = <1>;
+		vfront-porch = <1>;
+	};
+	def-back-color-red = <0x0>;
+	def-back-color-green = <0x0>;
+	def-back-color-blue = <0x0>;
+};