drm/panel: Add support for ARM Versatile panels

The ARM reference designs "Versatile AB" and "Versatile PB"
contain panel connectors with autodetection of the connected
panel type. This adds a small driver utilizing the MFD syscon
look-up to read the autodetection register and set up the
corresponding panel appropriately.

In the source file there is a bit of elaboration of the
panel types and interfaces on these boards.

This was tested with the PL111 DRM driver on the ARM Versatile
AB with the IB2 daughterboard.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205192013.5349-2-linus.walleij@linaro.org

MAINTAINERS

@@ -4442,6 +4442,13 @@ T:	git git://anongit.freedesktop.org/drm/drm-misc
 S:	Supported
 F:	drivers/gpu/drm/pl111/
 
+DRM DRIVER FOR ARM VERSATILE TFT PANELS
+M:	Linus Walleij <linus.walleij@linaro.org>
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+S:	Maintained
+F:	drivers/gpu/drm/panel/panel-arm-versatile.c
+F:	Documentation/devicetree/bindings/display/panel/arm,versatile-tft-panel.txt
+
 DRM DRIVER FOR AST SERVER GRAPHICS CHIPS
 M:	Dave Airlie <airlied@redhat.com>
 S:	Odd Fixes

drivers/gpu/drm/panel/Kconfig

@@ -7,6 +7,16 @@ config DRM_PANEL
 menu "Display Panels"
 	depends on DRM && DRM_PANEL
 
+config DRM_PANEL_ARM_VERSATILE
+	tristate "ARM Versatile panel driver"
+	depends on OF
+	depends on MFD_SYSCON
+	select VIDEOMODE_HELPERS
+	help
+	  This driver supports the ARM Versatile panels connected to ARM
+	  reference designs. The panel is detected using special registers
+	  in the Versatile family syscon registers.
+
 config DRM_PANEL_LVDS
 	tristate "Generic LVDS panel driver"
 	depends on OF

drivers/gpu/drm/panel/Makefile

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_DRM_PANEL_ARM_VERSATILE) += panel-arm-versatile.o
 obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
 obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
 obj-$(CONFIG_DRM_PANEL_ILITEK_IL9322) += panel-ilitek-ili9322.o

drivers/gpu/drm/panel/panel-arm-versatile.c

@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Panel driver for the ARM Versatile family reference designs from
+ * ARM Limited.
+ *
+ * Author:
+ * Linus Walleij <linus.wallei@linaro.org>
+ *
+ * On the Versatile AB, these panels come mounted on daughterboards
+ * named "IB1" or "IB2" (Interface Board 1 & 2 respectively.) They
+ * are documented in ARM DUI 0225D Appendix C and D. These daughter
+ * boards support TFT display panels.
+ *
+ * - The IB1 is a passive board where the display connector defines a
+ *   few wires for encoding the display type for autodetection,
+ *   suitable display settings can then be looked up from this setting.
+ *   The magic bits can be read out from the system controller.
+ *
+ * - The IB2 is a more complex board intended for GSM phone development
+ *   with some logic and a control register, which needs to be accessed
+ *   and the board display needs to be turned on explicitly.
+ *
+ * On the Versatile PB, a special CLCD adaptor board is available
+ * supporting the same displays as the Versatile AB, plus one more
+ * Epson QCIF display.
+ *
+ */
+#include <drm/drmP.h>
+#include <drm/drm_panel.h>
+
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include <video/of_videomode.h>
+#include <video/videomode.h>
+
+/*
+ * This configuration register in the Versatile and RealView
+ * family is uniformly present but appears more and more
+ * unutilized starting with the RealView series.
+ */
+#define SYS_CLCD			0x50
+
+/* The Versatile can detect the connected panel type */
+#define SYS_CLCD_CLCDID_MASK		(BIT(8)|BIT(9)|BIT(10)|BIT(11)|BIT(12))
+#define SYS_CLCD_ID_SANYO_3_8		(0x00 << 8)
+#define SYS_CLCD_ID_SHARP_8_4		(0x01 << 8)
+#define SYS_CLCD_ID_EPSON_2_2		(0x02 << 8)
+#define SYS_CLCD_ID_SANYO_2_5		(0x07 << 8)
+#define SYS_CLCD_ID_VGA			(0x1f << 8)
+
+/* IB2 control register for the Versatile daughterboard */
+#define IB2_CTRL			0x00
+#define IB2_CTRL_LCD_SD			BIT(1) /* 1 = shut down LCD */
+#define IB2_CTRL_LCD_BL_ON		BIT(0)
+#define IB2_CTRL_LCD_MASK		(BIT(0)|BIT(1))
+
+/**
+ * struct versatile_panel_type - lookup struct for the supported panels
+ */
+struct versatile_panel_type {
+	/**
+	 * @name: the name of this panel
+	 */
+	const char *name;
+	/**
+	 * @magic: the magic value from the detection register
+	 */
+	u32 magic;
+	/**
+	 * @mode: the DRM display mode for this panel
+	 */
+	struct drm_display_mode mode;
+	/**
+	 * @bus_flags: the DRM bus flags for this panel e.g. inverted clock
+	 */
+	u32 bus_flags;
+	/**
+	 * @width_mm: the panel width in mm
+	 */
+	u32 width_mm;
+	/**
+	 * @height_mm: the panel height in mm
+	 */
+	u32 height_mm;
+	/**
+	 * @ib2: the panel may be connected on an IB2 daughterboard
+	 */
+	bool ib2;
+};
+
+/**
+ * struct versatile_panel - state container for the Versatile panels
+ */
+struct versatile_panel {
+	/**
+	 * @dev: the container device
+	 */
+	struct device *dev;
+	/**
+	 * @panel: the DRM panel instance for this device
+	 */
+	struct drm_panel panel;
+	/**
+	 * @panel_type: the Versatile panel type as detected
+	 */
+	const struct versatile_panel_type *panel_type;
+	/**
+	 * @map: map to the parent syscon where the main register reside
+	 */
+	struct regmap *map;
+	/**
+	 * @ib2_map: map to the IB2 syscon, if applicable
+	 */
+	struct regmap *ib2_map;
+};
+
+static const struct versatile_panel_type versatile_panels[] = {
+	/*
+	 * Sanyo TM38QV67A02A - 3.8 inch QVGA (320x240) Color TFT
+	 * found on the Versatile AB IB1 connector or the Versatile
+	 * PB adaptor board connector.
+	 */
+	{
+		.name = "Sanyo TM38QV67A02A",
+		.magic = SYS_CLCD_ID_SANYO_3_8,
+		.width_mm = 79,
+		.height_mm = 54,
+		.mode = {
+			.clock = 10000000,
+			.hdisplay = 320,
+			.hsync_start = 320 + 6,
+			.hsync_end = 320 + 6 + 6,
+			.htotal = 320 + 6 + 6 + 6,
+			.vdisplay = 240,
+			.vsync_start = 240 + 5,
+			.vsync_end = 240 + 5 + 6,
+			.vtotal = 240 + 5 + 6 + 5,
+			.vrefresh = 116,
+			.flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC,
+		},
+	},
+	/*
+	 * Sharp LQ084V1DG21 640x480 VGA Color TFT module
+	 * found on the Versatile AB IB1 connector or the Versatile
+	 * PB adaptor board connector.
+	 */
+	{
+		.name = "Sharp LQ084V1DG21",
+		.magic = SYS_CLCD_ID_SHARP_8_4,
+		.width_mm = 171,
+		.height_mm = 130,
+		.mode = {
+			.clock = 25000000,
+			.hdisplay = 640,
+			.hsync_start = 640 + 24,
+			.hsync_end = 640 + 24 + 96,
+			.htotal = 640 + 24 + 96 + 24,
+			.vdisplay = 480,
+			.vsync_start = 480 + 11,
+			.vsync_end = 480 + 11 + 2,
+			.vtotal = 480 + 11 + 2 + 32,
+			.vrefresh = 60,
+			.flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC,
+		},
+	},
+	/*
+	 * Epson L2F50113T00 - 2.2 inch QCIF 176x220 Color TFT
+	 * found on the Versatile PB adaptor board connector.
+	 */
+	{
+		.name = "Epson L2F50113T00",
+		.magic = SYS_CLCD_ID_EPSON_2_2,
+		.width_mm = 34,
+		.height_mm = 45,
+		.mode = {
+			.clock = 625000000,
+			.hdisplay = 176,
+			.hsync_start = 176 + 2,
+			.hsync_end = 176 + 2 + 3,
+			.htotal = 176 + 2 + 3 + 3,
+			.vdisplay = 220,
+			.vsync_start = 220 + 0,
+			.vsync_end = 220 + 0 + 2,
+			.vtotal = 220 + 0 + 2 + 1,
+			.vrefresh = 390,
+			.flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC,
+		},
+		.bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
+	},
+	/*
+	 * Sanyo ALR252RGT 240x320 portrait display found on the
+	 * Versatile AB IB2 daughterboard for GSM prototyping.
+	 */
+	{
+		.name = "Sanyo ALR252RGT",
+		.magic = SYS_CLCD_ID_SANYO_2_5,
+		.width_mm = 37,
+		.height_mm = 50,
+		.mode = {
+			.clock = 5400000,
+			.hdisplay = 240,
+			.hsync_start = 240 + 10,
+			.hsync_end = 240 + 10 + 10,
+			.htotal = 240 + 10 + 10 + 20,
+			.vdisplay = 320,
+			.vsync_start = 320 + 2,
+			.vsync_end = 320 + 2 + 2,
+			.vtotal = 320 + 2 + 2 + 2,
+			.vrefresh = 116,
+			.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
+		},
+		.bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
+		.ib2 = true,
+	},
+};
+
+static inline struct versatile_panel *
+to_versatile_panel(struct drm_panel *panel)
+{
+	return container_of(panel, struct versatile_panel, panel);
+}
+
+static int versatile_panel_disable(struct drm_panel *panel)
+{
+	struct versatile_panel *vpanel = to_versatile_panel(panel);
+
+	/* If we're on an IB2 daughterboard, turn off display */
+	if (vpanel->ib2_map) {
+		dev_dbg(vpanel->dev, "disable IB2 display\n");
+		regmap_update_bits(vpanel->ib2_map,
+				   IB2_CTRL,
+				   IB2_CTRL_LCD_MASK,
+				   IB2_CTRL_LCD_SD);
+	}
+
+	return 0;
+}
+
+static int versatile_panel_enable(struct drm_panel *panel)
+{
+	struct versatile_panel *vpanel = to_versatile_panel(panel);
+
+	/* If we're on an IB2 daughterboard, turn on display */
+	if (vpanel->ib2_map) {
+		dev_dbg(vpanel->dev, "enable IB2 display\n");
+		regmap_update_bits(vpanel->ib2_map,
+				   IB2_CTRL,
+				   IB2_CTRL_LCD_MASK,
+				   IB2_CTRL_LCD_BL_ON);
+	}
+
+	return 0;
+}
+
+static int versatile_panel_get_modes(struct drm_panel *panel)
+{
+	struct drm_connector *connector = panel->connector;
+	struct versatile_panel *vpanel = to_versatile_panel(panel);
+	struct drm_display_mode *mode;
+
+	strncpy(connector->display_info.name, vpanel->panel_type->name,
+		DRM_DISPLAY_INFO_LEN);
+	connector->display_info.width_mm = vpanel->panel_type->width_mm;
+	connector->display_info.height_mm = vpanel->panel_type->height_mm;
+	connector->display_info.bus_flags = vpanel->panel_type->bus_flags;
+
+	mode = drm_mode_duplicate(panel->drm, &vpanel->panel_type->mode);
+	drm_mode_set_name(mode);
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	mode->width_mm = vpanel->panel_type->width_mm;
+	mode->height_mm = vpanel->panel_type->height_mm;
+	drm_mode_probed_add(connector, mode);
+
+	return 1;
+}
+
+static const struct drm_panel_funcs versatile_panel_drm_funcs = {
+	.disable = versatile_panel_disable,
+	.enable = versatile_panel_enable,
+	.get_modes = versatile_panel_get_modes,
+};
+
+static int versatile_panel_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct versatile_panel *vpanel;
+	struct device *parent;
+	struct regmap *map;
+	int ret;
+	u32 val;
+	int i;
+
+	parent = dev->parent;
+	if (!parent) {
+		dev_err(dev, "no parent for versatile panel\n");
+		return -ENODEV;
+	}
+	map = syscon_node_to_regmap(parent->of_node);
+	if (IS_ERR(map)) {
+		dev_err(dev, "no regmap for versatile panel parent\n");
+		return PTR_ERR(map);
+	}
+
+	vpanel = devm_kzalloc(dev, sizeof(*vpanel), GFP_KERNEL);
+	if (!vpanel)
+		return -ENOMEM;
+
+	ret = regmap_read(map, SYS_CLCD, &val);
+	if (ret) {
+		dev_err(dev, "cannot access syscon regs\n");
+		return ret;
+	}
+
+	val &= SYS_CLCD_CLCDID_MASK;
+
+	for (i = 0; i < ARRAY_SIZE(versatile_panels); i++) {
+		const struct versatile_panel_type *pt;
+
+		pt = &versatile_panels[i];
+		if (pt->magic == val) {
+			vpanel->panel_type = pt;
+			break;
+		}
+	}
+
+	/* No panel detected or VGA, let's leave this show */
+	if (i == ARRAY_SIZE(versatile_panels)) {
+		dev_info(dev, "no panel detected\n");
+		return -ENODEV;
+	}
+
+	dev_info(dev, "detected: %s\n", vpanel->panel_type->name);
+	vpanel->dev = dev;
+	vpanel->map = map;
+
+	/* Check if the panel is mounted on an IB2 daughterboard */
+	if (vpanel->panel_type->ib2) {
+		vpanel->ib2_map = syscon_regmap_lookup_by_compatible(
+			"arm,versatile-ib2-syscon");
+		if (IS_ERR(vpanel->ib2_map))
+			vpanel->ib2_map = NULL;
+		else
+			dev_info(dev, "panel mounted on IB2 daughterboard\n");
+	}
+
+	drm_panel_init(&vpanel->panel);
+	vpanel->panel.dev = dev;
+	vpanel->panel.funcs = &versatile_panel_drm_funcs;
+
+	return drm_panel_add(&vpanel->panel);
+}
+
+static const struct of_device_id versatile_panel_match[] = {
+	{ .compatible = "arm,versatile-tft-panel", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, versatile_panel_match);
+
+static struct platform_driver versatile_panel_driver = {
+	.probe		= versatile_panel_probe,
+	.driver		= {
+		.name	= "versatile-tft-panel",
+		.of_match_table = versatile_panel_match,
+	},
+};
+module_platform_driver(versatile_panel_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("ARM Versatile panel driver");
+MODULE_LICENSE("GPL v2");