drm/tiny: Add MIPI DBI compatible SPI driver

Add a driver that will work with most MIPI DBI compatible SPI panels.
This avoids adding a driver for every new MIPI DBI compatible controller
that is to be used by Linux. The 'compatible' Device Tree property with
a '.bin' suffix will be used to load a firmware file that contains the
controller configuration.

Example (driver will load sainsmart18.bin):

display@0 {
	compatible = "sainsmart18", "panel-mipi-dbi-spi";
...
};

v5:
- kconfig: s/DRM_KMS_CMA_HELPER/DRM_GEM_CMA_HELPER/ (Sam)
- kconfig: Add select VIDEOMODE_HELPERS (Sam)
- kconfig: Add wiki url in the description (Sam)
- Split out and use of_get_drm_panel_display_mode()(Sam)
- Only use the first compatible to look for a firmware file since the
  binding mandates 2 compatibles.
- Make having a firmware file mandatory so we can print an error
  message if it's missing to improve the user experience. It's very
  unlikely that a controller doesn't need to be initialized and if
  it doesn't, it's possible to have a firmware file containing only
  a DCS NOP.

v4:
- Move driver to drm/tiny where the other drivers of its kind are located.
  The driver module will not be shared with a future DPI driver after all.

v3:
- Move properties to DT (Maxime)
- The MIPI DPI spec has optional support for DPI where the controller is
  configured over DBI. Rework the command functions so they can be moved
  to drm_mipi_dbi and shared with a future panel-mipi-dpi-spi driver

v2:
- Drop model property and use compatible instead (Rob)
- Add wiki entry in MAINTAINERS

Acked-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220227124713.39766-6-noralf@tronnes.org

MAINTAINERS

@@ -6107,6 +6107,14 @@ T:	git git://anongit.freedesktop.org/drm/drm-misc
 F:	Documentation/devicetree/bindings/display/multi-inno,mi0283qt.txt
 F:	drivers/gpu/drm/tiny/mi0283qt.c
 
+DRM DRIVER FOR MIPI DBI compatible panels
+M:	Noralf Trønnes <noralf@tronnes.org>
+S:	Maintained
+W:	https://github.com/notro/panel-mipi-dbi/wiki
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+F:	Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
+F:	drivers/gpu/drm/tiny/panel-mipi-dbi.c
+
 DRM DRIVER FOR MSM ADRENO GPU
 M:	Rob Clark <robdclark@gmail.com>
 M:	Sean Paul <sean@poorly.run>

drivers/gpu/drm/tiny/Kconfig

@@ -51,6 +51,21 @@ config DRM_GM12U320
 	 This is a KMS driver for projectors which use the GM12U320 chipset
 	 for video transfer over USB2/3, such as the Acer C120 mini projector.
 
+config DRM_PANEL_MIPI_DBI
+	tristate "DRM support for MIPI DBI compatible panels"
+	depends on DRM && SPI
+	select DRM_KMS_HELPER
+	select DRM_GEM_CMA_HELPER
+	select DRM_MIPI_DBI
+	select BACKLIGHT_CLASS_DEVICE
+	select VIDEOMODE_HELPERS
+	help
+	  Say Y here if you want to enable support for MIPI DBI compatible
+	  panels. The controller command setup can be provided using a
+	  firmware file. For more information see
+	  https://github.com/notro/panel-mipi-dbi/wiki.
+	  To compile this driver as a module, choose M here.
+
 config DRM_SIMPLEDRM
 	tristate "Simple framebuffer driver"
 	depends on DRM && MMU

drivers/gpu/drm/tiny/Makefile

@@ -4,6 +4,7 @@ obj-$(CONFIG_DRM_ARCPGU)		+= arcpgu.o
 obj-$(CONFIG_DRM_BOCHS)			+= bochs.o
 obj-$(CONFIG_DRM_CIRRUS_QEMU)		+= cirrus.o
 obj-$(CONFIG_DRM_GM12U320)		+= gm12u320.o
+obj-$(CONFIG_DRM_PANEL_MIPI_DBI)	+= panel-mipi-dbi.o
 obj-$(CONFIG_DRM_SIMPLEDRM)		+= simpledrm.o
 obj-$(CONFIG_TINYDRM_HX8357D)		+= hx8357d.o
 obj-$(CONFIG_TINYDRM_ILI9163)		+= ili9163.o

drivers/gpu/drm/tiny/panel-mipi-dbi.c

@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DRM driver for MIPI DBI compatible display panels
+ *
+ * Copyright 2022 Noralf Trønnes
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_cma_helper.h>
+#include <drm/drm_managed.h>
+#include <drm/drm_mipi_dbi.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_modeset_helper.h>
+
+#include <video/mipi_display.h>
+
+static const u8 panel_mipi_dbi_magic[15] = { 'M', 'I', 'P', 'I', ' ', 'D', 'B', 'I',
+					     0, 0, 0, 0, 0, 0, 0 };
+
+/*
+ * The display controller configuration is stored in a firmware file.
+ * The Device Tree 'compatible' property value with a '.bin' suffix is passed
+ * to request_firmware() to fetch this file.
+ */
+struct panel_mipi_dbi_config {
+	/* Magic string: panel_mipi_dbi_magic */
+	u8 magic[15];
+
+	/* Config file format version */
+	u8 file_format_version;
+
+	/*
+	 * MIPI commands to execute when the display pipeline is enabled.
+	 * This is used to configure the display controller.
+	 *
+	 * The commands are stored in a byte array with the format:
+	 *     command, num_parameters, [ parameter, ...], command, ...
+	 *
+	 * Some commands require a pause before the next command can be received.
+	 * Inserting a delay in the command sequence is done by using the NOP command with one
+	 * parameter: delay in miliseconds (the No Operation command is part of the MIPI Display
+	 * Command Set where it has no parameters).
+	 *
+	 * Example:
+	 *     command 0x11
+	 *     sleep 120ms
+	 *     command 0xb1 parameters 0x01, 0x2c, 0x2d
+	 *     command 0x29
+	 *
+	 * Byte sequence:
+	 *     0x11 0x00
+	 *     0x00 0x01 0x78
+	 *     0xb1 0x03 0x01 0x2c 0x2d
+	 *     0x29 0x00
+	 */
+	u8 commands[];
+};
+
+struct panel_mipi_dbi_commands {
+	const u8 *buf;
+	size_t len;
+};
+
+static struct panel_mipi_dbi_commands *
+panel_mipi_dbi_check_commands(struct device *dev, const struct firmware *fw)
+{
+	const struct panel_mipi_dbi_config *config = (struct panel_mipi_dbi_config *)fw->data;
+	struct panel_mipi_dbi_commands *commands;
+	size_t size = fw->size, commands_len;
+	unsigned int i = 0;
+
+	if (size < sizeof(*config) + 2) { /* At least 1 command */
+		dev_err(dev, "config: file size=%zu is too small\n", size);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (memcmp(config->magic, panel_mipi_dbi_magic, sizeof(config->magic))) {
+		dev_err(dev, "config: Bad magic: %15ph\n", config->magic);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (config->file_format_version != 1) {
+		dev_err(dev, "config: version=%u is not supported\n", config->file_format_version);
+		return ERR_PTR(-EINVAL);
+	}
+
+	drm_dev_dbg(dev, DRM_UT_DRIVER, "size=%zu version=%u\n", size, config->file_format_version);
+
+	commands_len = size - sizeof(*config);
+
+	while ((i + 1) < commands_len) {
+		u8 command = config->commands[i++];
+		u8 num_parameters = config->commands[i++];
+		const u8 *parameters = &config->commands[i];
+
+		i += num_parameters;
+		if (i > commands_len) {
+			dev_err(dev, "config: command=0x%02x num_parameters=%u overflows\n",
+				command, num_parameters);
+			return ERR_PTR(-EINVAL);
+		}
+
+		if (command == 0x00 && num_parameters == 1)
+			drm_dev_dbg(dev, DRM_UT_DRIVER, "sleep %ums\n", parameters[0]);
+		else
+			drm_dev_dbg(dev, DRM_UT_DRIVER, "command %02x %*ph\n",
+				    command, num_parameters, parameters);
+	}
+
+	if (i != commands_len) {
+		dev_err(dev, "config: malformed command array\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	commands = devm_kzalloc(dev, sizeof(*commands), GFP_KERNEL);
+	if (!commands)
+		return ERR_PTR(-ENOMEM);
+
+	commands->len = commands_len;
+	commands->buf = devm_kmemdup(dev, config->commands, commands->len, GFP_KERNEL);
+	if (!commands->buf)
+		return ERR_PTR(-ENOMEM);
+
+	return commands;
+}
+
+static struct panel_mipi_dbi_commands *panel_mipi_dbi_commands_from_fw(struct device *dev)
+{
+	struct panel_mipi_dbi_commands *commands;
+	const struct firmware *fw;
+	const char *compatible;
+	char fw_name[40];
+	int ret;
+
+	ret = of_property_read_string_index(dev->of_node, "compatible", 0, &compatible);
+	if (ret)
+		return ERR_PTR(ret);
+
+	snprintf(fw_name, sizeof(fw_name), "%s.bin", compatible);
+	ret = request_firmware(&fw, fw_name, dev);
+	if (ret) {
+		dev_err(dev, "No config file found for compatible '%s' (error=%d)\n",
+			compatible, ret);
+
+		return ERR_PTR(ret);
+	}
+
+	commands = panel_mipi_dbi_check_commands(dev, fw);
+	release_firmware(fw);
+
+	return commands;
+}
+
+static void panel_mipi_dbi_commands_execute(struct mipi_dbi *dbi,
+					    struct panel_mipi_dbi_commands *commands)
+{
+	unsigned int i = 0;
+
+	if (!commands)
+		return;
+
+	while (i < commands->len) {
+		u8 command = commands->buf[i++];
+		u8 num_parameters = commands->buf[i++];
+		const u8 *parameters = &commands->buf[i];
+
+		if (command == 0x00 && num_parameters == 1)
+			msleep(parameters[0]);
+		else if (num_parameters)
+			mipi_dbi_command_stackbuf(dbi, command, parameters, num_parameters);
+		else
+			mipi_dbi_command(dbi, command);
+
+		i += num_parameters;
+	}
+}
+
+static void panel_mipi_dbi_enable(struct drm_simple_display_pipe *pipe,
+				  struct drm_crtc_state *crtc_state,
+				  struct drm_plane_state *plane_state)
+{
+	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(pipe->crtc.dev);
+	struct mipi_dbi *dbi = &dbidev->dbi;
+	int ret, idx;
+
+	if (!drm_dev_enter(pipe->crtc.dev, &idx))
+		return;
+
+	drm_dbg(pipe->crtc.dev, "\n");
+
+	ret = mipi_dbi_poweron_conditional_reset(dbidev);
+	if (ret < 0)
+		goto out_exit;
+	if (!ret)
+		panel_mipi_dbi_commands_execute(dbi, dbidev->driver_private);
+
+	mipi_dbi_enable_flush(dbidev, crtc_state, plane_state);
+out_exit:
+	drm_dev_exit(idx);
+}
+
+static const struct drm_simple_display_pipe_funcs panel_mipi_dbi_pipe_funcs = {
+	.enable = panel_mipi_dbi_enable,
+	.disable = mipi_dbi_pipe_disable,
+	.update = mipi_dbi_pipe_update,
+};
+
+DEFINE_DRM_GEM_CMA_FOPS(panel_mipi_dbi_fops);
+
+static const struct drm_driver panel_mipi_dbi_driver = {
+	.driver_features	= DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
+	.fops			= &panel_mipi_dbi_fops,
+	DRM_GEM_CMA_DRIVER_OPS_VMAP,
+	.debugfs_init		= mipi_dbi_debugfs_init,
+	.name			= "panel-mipi-dbi",
+	.desc			= "MIPI DBI compatible display panel",
+	.date			= "20220103",
+	.major			= 1,
+	.minor			= 0,
+};
+
+static int panel_mipi_dbi_get_mode(struct mipi_dbi_dev *dbidev, struct drm_display_mode *mode)
+{
+	struct device *dev = dbidev->drm.dev;
+	u16 hback_porch, vback_porch;
+	int ret;
+
+	ret = of_get_drm_panel_display_mode(dev->of_node, mode, NULL);
+	if (ret) {
+		dev_err(dev, "%pOF: failed to get panel-timing (error=%d)\n", dev->of_node, ret);
+		return ret;
+	}
+
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	hback_porch = mode->htotal - mode->hsync_end;
+	vback_porch = mode->vtotal - mode->vsync_end;
+
+	/*
+	 * Make sure width and height are set and that only back porch and
+	 * pixelclock are set in the other timing values. Also check that
+	 * width and height don't exceed the 16-bit value specified by MIPI DCS.
+	 */
+	if (!mode->hdisplay || !mode->vdisplay || mode->flags ||
+	    mode->hsync_end > mode->hdisplay || (hback_porch + mode->hdisplay) > 0xffff ||
+	    mode->vsync_end > mode->vdisplay || (vback_porch + mode->vdisplay) > 0xffff) {
+		dev_err(dev, "%pOF: panel-timing out of bounds\n", dev->of_node);
+		return -EINVAL;
+	}
+
+	/* The driver doesn't use the pixel clock but it is mandatory so fake one if not set */
+	if (!mode->clock)
+		mode->clock = mode->htotal * mode->vtotal * 60 / 1000;
+
+	dbidev->top_offset = vback_porch;
+	dbidev->left_offset = hback_porch;
+
+	return 0;
+}
+
+static int panel_mipi_dbi_spi_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct drm_display_mode mode;
+	struct mipi_dbi_dev *dbidev;
+	struct drm_device *drm;
+	struct mipi_dbi *dbi;
+	struct gpio_desc *dc;
+	int ret;
+
+	dbidev = devm_drm_dev_alloc(dev, &panel_mipi_dbi_driver, struct mipi_dbi_dev, drm);
+	if (IS_ERR(dbidev))
+		return PTR_ERR(dbidev);
+
+	dbi = &dbidev->dbi;
+	drm = &dbidev->drm;
+
+	ret = panel_mipi_dbi_get_mode(dbidev, &mode);
+	if (ret)
+		return ret;
+
+	dbidev->regulator = devm_regulator_get(dev, "power");
+	if (IS_ERR(dbidev->regulator))
+		return dev_err_probe(dev, PTR_ERR(dbidev->regulator),
+				     "Failed to get regulator 'power'\n");
+
+	dbidev->backlight = devm_of_find_backlight(dev);
+	if (IS_ERR(dbidev->backlight))
+		return dev_err_probe(dev, PTR_ERR(dbidev->backlight), "Failed to get backlight\n");
+
+	dbi->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(dbi->reset))
+		return dev_err_probe(dev, PTR_ERR(dbi->reset), "Failed to get GPIO 'reset'\n");
+
+	dc = devm_gpiod_get_optional(dev, "dc", GPIOD_OUT_LOW);
+	if (IS_ERR(dc))
+		return dev_err_probe(dev, PTR_ERR(dc), "Failed to get GPIO 'dc'\n");
+
+	ret = mipi_dbi_spi_init(spi, dbi, dc);
+	if (ret)
+		return ret;
+
+	if (device_property_present(dev, "write-only"))
+		dbi->read_commands = NULL;
+
+	dbidev->driver_private = panel_mipi_dbi_commands_from_fw(dev);
+	if (IS_ERR(dbidev->driver_private))
+		return PTR_ERR(dbidev->driver_private);
+
+	ret = mipi_dbi_dev_init(dbidev, &panel_mipi_dbi_pipe_funcs, &mode, 0);
+	if (ret)
+		return ret;
+
+	drm_mode_config_reset(drm);
+
+	ret = drm_dev_register(drm, 0);
+	if (ret)
+		return ret;
+
+	spi_set_drvdata(spi, drm);
+
+	drm_fbdev_generic_setup(drm, 0);
+
+	return 0;
+}
+
+static int panel_mipi_dbi_spi_remove(struct spi_device *spi)
+{
+	struct drm_device *drm = spi_get_drvdata(spi);
+
+	drm_dev_unplug(drm);
+	drm_atomic_helper_shutdown(drm);
+
+	return 0;
+}
+
+static void panel_mipi_dbi_spi_shutdown(struct spi_device *spi)
+{
+	drm_atomic_helper_shutdown(spi_get_drvdata(spi));
+}
+
+static int __maybe_unused panel_mipi_dbi_pm_suspend(struct device *dev)
+{
+	return drm_mode_config_helper_suspend(dev_get_drvdata(dev));
+}
+
+static int __maybe_unused panel_mipi_dbi_pm_resume(struct device *dev)
+{
+	drm_mode_config_helper_resume(dev_get_drvdata(dev));
+
+	return 0;
+}
+
+static const struct dev_pm_ops panel_mipi_dbi_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(panel_mipi_dbi_pm_suspend, panel_mipi_dbi_pm_resume)
+};
+
+static const struct of_device_id panel_mipi_dbi_spi_of_match[] = {
+	{ .compatible = "panel-mipi-dbi-spi" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, panel_mipi_dbi_spi_of_match);
+
+static const struct spi_device_id panel_mipi_dbi_spi_id[] = {
+	{ "panel-mipi-dbi-spi", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, panel_mipi_dbi_spi_id);
+
+static struct spi_driver panel_mipi_dbi_spi_driver = {
+	.driver = {
+		.name = "panel-mipi-dbi-spi",
+		.owner = THIS_MODULE,
+		.of_match_table = panel_mipi_dbi_spi_of_match,
+		.pm = &panel_mipi_dbi_pm_ops,
+	},
+	.id_table = panel_mipi_dbi_spi_id,
+	.probe = panel_mipi_dbi_spi_probe,
+	.remove = panel_mipi_dbi_spi_remove,
+	.shutdown = panel_mipi_dbi_spi_shutdown,
+};
+module_spi_driver(panel_mipi_dbi_spi_driver);
+
+MODULE_DESCRIPTION("MIPI DBI compatible display panel driver");
+MODULE_AUTHOR("Noralf Trønnes");
+MODULE_LICENSE("GPL");