drm/panel: st7701: Add support for SPI for configuration

The ST7701 supports not only MIPI DSI, but also SPI as an interface
for configuration. To support a panel connected via SPI with an RGB
parallel interface, add support for SPI using MIPI DBI helpers.

Signed-off-by: Hironori KIKUCHI <[e-mail]>
Reviewed-by: Neil Armstrong <[e-mail]>
Reviewed-by: Jessica Zhang <[e-mail]>
Reviewed-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/panel/Kconfig

···
 config DRM_PANEL_SITRONIX_ST7701
 	tristate "Sitronix ST7701 panel driver"
 	depends on OF
-	depends on DRM_MIPI_DSI
+	depends on SPI || DRM_MIPI_DSI
+	select DRM_MIPI_DBI if SPI
 	depends on BACKLIGHT_CLASS_DEVICE
 	help
 	  Say Y here if you want to enable support for the Sitronix

drivers/gpu/drm/panel/panel-sitronix-st7701.c

···
  * Author: Jagan Teki <[e-mail]>
  */
 
+#include <drm/drm_mipi_dbi.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_modes.h>
 #include <drm/drm_panel.h>
···
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
 
 #include <video/mipi_display.h>
 
···
 struct st7701 {
 	struct drm_panel panel;
 	struct mipi_dsi_device *dsi;
+	struct mipi_dbi dbi;
 	const struct st7701_panel_desc *desc;
 
 	struct regulator_bulk_data supplies[2];
 	struct gpio_desc *reset;
 	unsigned int sleep_delay;
 	enum drm_panel_orientation orientation;
+
+	int (*write_command)(struct st7701 *st7701, u8 cmd, const u8 *seq,
+			     size_t len);
 };
 
 static inline struct st7701 *panel_to_st7701(struct drm_panel *panel)
···
 	return container_of(panel, struct st7701, panel);
 }
 
-static inline int st7701_dsi_write(struct st7701 *st7701, const void *seq,
-				   size_t len)
+static int st7701_dsi_write(struct st7701 *st7701, u8 cmd, const u8 *seq,
+			    size_t len)
 {
-	return mipi_dsi_dcs_write_buffer(st7701->dsi, seq, len);
+	return mipi_dsi_dcs_write(st7701->dsi, cmd, seq, len);
 }
 
-#define ST7701_WRITE(st7701, seq...)				\
-	{							\
-		const u8 d[] = { seq };				\
-		st7701_dsi_write(st7701, d, ARRAY_SIZE(d));	\
+static int st7701_dbi_write(struct st7701 *st7701, u8 cmd, const u8 *seq,
+			    size_t len)
+{
+	return mipi_dbi_command_stackbuf(&st7701->dbi, cmd, seq, len);
+}
+
+#define ST7701_WRITE(st7701, cmd, seq...)				\
+	{								\
+		const u8 d[] = { seq };					\
+		st7701->write_command(st7701, cmd, d, ARRAY_SIZE(d));	\
 	}
 
 static u8 st7701_vgls_map(struct st7701 *st7701)
···
 	/* Command2, BK0 */
 	st7701_switch_cmd_bkx(st7701, true, 0);
 
-	mipi_dsi_dcs_write(st7701->dsi, ST7701_CMD2_BK0_PVGAMCTRL,
-			   desc->pv_gamma, ARRAY_SIZE(desc->pv_gamma));
-	mipi_dsi_dcs_write(st7701->dsi, ST7701_CMD2_BK0_NVGAMCTRL,
-			   desc->nv_gamma, ARRAY_SIZE(desc->nv_gamma));
+	st7701->write_command(st7701, ST7701_CMD2_BK0_PVGAMCTRL, desc->pv_gamma,
+			      ARRAY_SIZE(desc->pv_gamma));
+	st7701->write_command(st7701, ST7701_CMD2_BK0_NVGAMCTRL, desc->nv_gamma,
+			      ARRAY_SIZE(desc->nv_gamma));
 	/*
 	 * Vertical line count configuration:
 	 * Line[6:0]: select number of vertical lines of the TFT matrix in
···
 
 	st7701 = dev_get_drvdata(&dsi->dev);
 	st7701->dsi = dsi;
+	st7701->write_command = st7701_dsi_write;
+
+	if (!st7701->desc->lanes)
+		return dev_err_probe(&dsi->dev, -EINVAL, "This panel is not for MIPI DSI\n");
 
 	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
 			  MIPI_DSI_MODE_LPM | MIPI_DSI_CLOCK_NON_CONTINUOUS;
···
 	return 0;
 }
 
+static int st7701_spi_probe(struct spi_device *spi)
+{
+	struct st7701 *st7701;
+	struct gpio_desc *dc;
+	int err;
+
+	err = st7701_probe(&spi->dev, DRM_MODE_CONNECTOR_DPI);
+	if (err)
+		return err;
+
+	st7701 = dev_get_drvdata(&spi->dev);
+	st7701->write_command = st7701_dbi_write;
+
+	dc = devm_gpiod_get_optional(&spi->dev, "dc", GPIOD_OUT_LOW);
+	if (IS_ERR(dc))
+		return dev_err_probe(&spi->dev, PTR_ERR(dc), "Failed to get GPIO for D/CX\n");
+
+	err = mipi_dbi_spi_init(spi, &st7701->dbi, dc);
+	if (err)
+		return dev_err_probe(&spi->dev, err, "Failed to init MIPI DBI\n");
+	st7701->dbi.read_commands = NULL;
+
+	return 0;
+}
+
 static void st7701_dsi_remove(struct mipi_dsi_device *dsi)
 {
 	mipi_dsi_detach(dsi);
 }
 
-static const struct of_device_id st7701_of_match[] = {
+static const struct of_device_id st7701_dsi_of_match[] = {
 	{ .compatible = "anbernic,rg-arc-panel", .data = &rg_arc_desc },
 	{ .compatible = "densitron,dmt028vghmcmi-1a", .data = &dmt028vghmcmi_1a_desc },
 	{ .compatible = "elida,kd50t048a", .data = &kd50t048a_desc },
 	{ .compatible = "techstar,ts8550b", .data = &ts8550b_desc },
 	{ }
 };
-MODULE_DEVICE_TABLE(of, st7701_of_match);
+MODULE_DEVICE_TABLE(of, st7701_dsi_of_match);
+
+static const struct of_device_id st7701_spi_of_match[] = {
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, st7701_spi_of_match);
+
+static const struct spi_device_id st7701_spi_ids[] = {
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, st7701_spi_ids);
 
 static struct mipi_dsi_driver st7701_dsi_driver = {
 	.probe		= st7701_dsi_probe,
 	.remove		= st7701_dsi_remove,
 	.driver = {
 		.name		= "st7701",
-		.of_match_table	= st7701_of_match,
+		.of_match_table	= st7701_dsi_of_match,
 	},
 };
-module_mipi_dsi_driver(st7701_dsi_driver);
+
+static struct spi_driver st7701_spi_driver = {
+	.probe		= st7701_spi_probe,
+	.id_table	= st7701_spi_ids,
+	.driver = {
+		.name		= "st7701",
+		.of_match_table	= st7701_spi_of_match,
+	},
+};
+
+static int __init st7701_driver_init(void)
+{
+	int err;
+
+	if (IS_ENABLED(CONFIG_SPI)) {
+		err = spi_register_driver(&st7701_spi_driver);
+		if (err)
+			return err;
+	}
+
+	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI)) {
+		err = mipi_dsi_driver_register(&st7701_dsi_driver);
+		if (err) {
+			if (IS_ENABLED(CONFIG_SPI))
+				spi_unregister_driver(&st7701_spi_driver);
+			return err;
+		}
+	}
+
+	return 0;
+}
+module_init(st7701_driver_init);
+
+static void __exit st7701_driver_exit(void)
+{
+	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI))
+		mipi_dsi_driver_unregister(&st7701_dsi_driver);
+
+	if (IS_ENABLED(CONFIG_SPI))
+		spi_unregister_driver(&st7701_spi_driver);
+}
+module_exit(st7701_driver_exit);
 
 MODULE_AUTHOR("Jagan Teki <[e-mail]>");
+MODULE_AUTHOR("Hironori KIKUCHI <[e-mail]>");
 MODULE_DESCRIPTION("Sitronix ST7701 LCD Panel Driver");
 MODULE_LICENSE("GPL");