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From: Ahmad Fatoum <a.fatoum@barebox.org>
To: barebox@lists.infradead.org
Cc: Ahmad Fatoum <a.fatoum@barebox.org>
Subject: [PATCH 4/4] commands: mipi_dsi: add command for easier DCS experimentation
Date: Sun,  8 Nov 2026 11:10:54 +0100
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 Content preview:  To simplify MIPI DSI panel bring up, add a mipi_dsi command
    along the same lines as the mipi_dbi, which lists DSI devices, sends DCS
   writes and reads back registers, so this can be done from the shell [...] 
 
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To simplify MIPI DSI panel bring up, add a mipi_dsi command along the
same lines as the mipi_dbi, which lists DSI devices, sends DCS writes
and reads back registers, so this can be done from the shell.

Like the mipi_dbi command, the register dump only reads known read
commands. The panel executes the command byte of a DCS read request:
dumping 0x00-0xff unconditionally soft-reset the OTM8009A on the
STM32MP157C-DK2 and put it into sleep mode.

Tested on the STM32MP157C-DK2 (OTM8009A) and the Powkiddy RGB30 (ST7703).

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 arch/arm/configs/stm32mp_defconfig |   1 +
 commands/Kconfig                   |  27 +++
 commands/Makefile                  |   1 +
 commands/mipi_dsi.c                | 355 +++++++++++++++++++++++++++++
 test/py/test_mipi_dsi.py           |  78 +++++++
 5 files changed, 462 insertions(+)
 create mode 100644 commands/mipi_dsi.c
 create mode 100644 test/py/test_mipi_dsi.py

diff --git a/arch/arm/configs/stm32mp_defconfig b/arch/arm/configs/stm32mp_defconfig
index e1aef7c86fc0..13aed489ccea 100644
--- a/arch/arm/configs/stm32mp_defconfig
+++ b/arch/arm/configs/stm32mp_defconfig
@@ -95,6 +95,7 @@ CONFIG_CMD_GPIO=y
 CONFIG_CMD_LED=y
 CONFIG_CMD_POWEROFF=y
 CONFIG_CMD_SPI=y
+CONFIG_CMD_MIPI_DSI=y
 CONFIG_CMD_USBGADGET=y
 CONFIG_CMD_WD=y
 CONFIG_CMD_BAREBOX_UPDATE=y
diff --git a/commands/Kconfig b/commands/Kconfig
index a43f0fbd4d40..eb4067d8108c 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -2263,6 +2263,33 @@ config CMD_MIPI_DBI
 		  -d DEVICE	select specific device (default is first registered)
 		  -w		issue write command
 
+config CMD_MIPI_DSI
+	bool
+	depends on DRIVER_VIDEO_MIPI_DSI
+	select PRINTF_HEXSTR
+	prompt "mipi_dsi command"
+	help
+	  read/write DCS registers of MIPI DSI devices
+
+	  Usage: mipi_dsi [-lvdinwgLH] [-c CH] [-p on|off] [CMD] [DATA...]
+
+	  Without CMD, dump the standard DCS registers.
+	  CMD and DATA bytes are given in hex.
+
+	  Options:
+		  -l		list all MIPI DSI devices
+		  -v		list with host, channel, lanes, format and mode flags
+		  -d DEVICE	select specific device (default is first registered)
+		  -i		read the panel identification registers
+		  -n LEN	number of bytes to read (default: known length, else 1)
+		  -w		issue write command
+		  -g		send generic packets: CMD and DATA are the payload,
+				reads take up to two bytes
+		  -p on|off	send Turn On or Shutdown Peripheral
+		  -c CH		use virtual channel CH (0-3)
+		  -L		send in low power mode
+		  -H		send in high speed mode
+
 config CMD_LED_TRIGGER
 	bool
 	depends on LED_TRIGGERS
diff --git a/commands/Makefile b/commands/Makefile
index 7dae582225f5..f91f6335ff8e 100644
--- a/commands/Makefile
+++ b/commands/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_CMD_I2C)		+= i2c.o
 obj-$(CONFIG_CMD_SPI)		+= spi.o
 obj-$(CONFIG_CMD_PWM)		+= pwm.o
 obj-$(CONFIG_CMD_MIPI_DBI)	+= mipi_dbi.o
+obj-$(CONFIG_CMD_MIPI_DSI)	+= mipi_dsi.o
 obj-$(CONFIG_CMD_UBI)		+= ubi.o
 obj-$(CONFIG_CMD_UBIFORMAT)	+= ubiformat.o
 obj-$(CONFIG_CMD_MENU)		+= menu.o
diff --git a/commands/mipi_dsi.c b/commands/mipi_dsi.c
new file mode 100644
index 000000000000..ccef279b9830
--- /dev/null
+++ b/commands/mipi_dsi.c
@@ -0,0 +1,355 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// SPDX-FileCopyrightText: © 2025 Ahmad Fatoum
+
+#include <command.h>
+#include <getopt.h>
+#include <video/mipi_dsi.h>
+#include <video/mipi_display.h>
+
+#define MIPI_DSI_CMD_MAX_LEN	64
+
+struct dcs_read {
+	u8 cmd;
+	u8 len;
+};
+
+/*
+ * Panels execute the command byte of a DCS read request like that of
+ * a write, so only ever send commands known to be reads.
+ */
+static const struct dcs_read dcs_reads[] = {
+	{ MIPI_DCS_GET_DISPLAY_ID, 3 },
+	{ MIPI_DCS_GET_RED_CHANNEL, 1 },
+	{ MIPI_DCS_GET_GREEN_CHANNEL, 1 },
+	{ MIPI_DCS_GET_BLUE_CHANNEL, 1 },
+	{ MIPI_DCS_GET_DISPLAY_STATUS, 4 },
+	{ MIPI_DCS_GET_POWER_MODE, 1 },
+	{ MIPI_DCS_GET_ADDRESS_MODE, 1 },
+	{ MIPI_DCS_GET_DISPLAY_MODE, 1 },
+	{ MIPI_DCS_GET_SIGNAL_MODE, 1 },
+	{ MIPI_DCS_GET_DIAGNOSTIC_RESULT, 1 },
+	{ MIPI_DCS_GET_SCANLINE, 2 },
+	{ MIPI_DCS_GET_DISPLAY_BRIGHTNESS, 1 },
+	{ MIPI_DCS_GET_CONTROL_DISPLAY, 1 },
+	{ MIPI_DCS_GET_CABC_MIN_BRIGHTNESS, 1 },
+};
+
+/* display ID, DDB and the nonstandard, but widespread ID1-ID3 */
+static const struct dcs_read dcs_ids[] = {
+	{ MIPI_DCS_GET_DISPLAY_ID, 3 },
+	{ MIPI_DCS_READ_DDB_START, 5 },
+	{ 0xda, 1 },
+	{ 0xdb, 1 },
+	{ 0xdc, 1 },
+};
+
+static const struct dcs_read *dcs_read_find(const struct dcs_read *reads,
+					    size_t nreads, u8 cmd)
+{
+	for (int i = 0; i < nreads; i++) {
+		if (reads[i].cmd == cmd)
+			return &reads[i];
+	}
+
+	return NULL;
+}
+
+static unsigned int dcs_read_len(u8 cmd)
+{
+	const struct dcs_read *reg;
+
+	reg = dcs_read_find(dcs_reads, ARRAY_SIZE(dcs_reads), cmd) ?:
+	      dcs_read_find(dcs_ids, ARRAY_SIZE(dcs_ids), cmd);
+
+	return reg ? reg->len : 1;
+}
+
+/*
+ * DCS reads send CMD, generic reads send CMD and up to one more
+ * parameter byte in @tx.
+ */
+static int mipi_dsi_command_show(struct mipi_dsi_device *dsi, bool generic,
+				 const u8 *tx, size_t tx_len, size_t len,
+				 bool prefix)
+{
+	u8 buf[MIPI_DSI_CMD_MAX_LEN];
+	ssize_t ret;
+
+	ret = mipi_dsi_set_maximum_return_packet_size(dsi, len);
+	if (!ret && generic)
+		ret = mipi_dsi_generic_read(dsi, tx, tx_len, buf, len);
+	else if (!ret)
+		ret = mipi_dsi_dcs_read(dsi, tx[0], buf, len);
+
+	if (prefix)
+		printf("%02x: ", tx[0]);
+
+	if (ret < 0) {
+		printf("read failed: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	printf("%*phN\n", (int)ret, buf);
+
+	return 0;
+}
+
+static int mipi_dsi_command_show_list(struct mipi_dsi_device *dsi,
+				      const struct dcs_read *reads,
+				      size_t nreads)
+{
+	int ret, err = 0;
+
+	for (int i = 0; i < nreads; i++) {
+		ret = mipi_dsi_command_show(dsi, false, &reads[i].cmd, 1,
+					    reads[i].len, true);
+		if (ret == -ENETDOWN)
+			return ret;
+		if (ret)
+			err = ret;
+		if (ctrlc())
+			return -EINTR;
+	}
+
+	return err;
+}
+
+static const char * const mipi_dsi_formats[] = {
+	[MIPI_DSI_FMT_RGB888] = "RGB888",
+	[MIPI_DSI_FMT_RGB666] = "RGB666",
+	[MIPI_DSI_FMT_RGB666_PACKED] = "RGB666_PACKED",
+	[MIPI_DSI_FMT_RGB565] = "RGB565",
+};
+
+static const char * const mipi_dsi_mode_flags[] = {
+	"video", "video-burst", "video-sync-pulse", "video-auto-vert",
+	"video-hse", "video-no-hfp", "video-no-hbp", "video-no-hsa",
+	"vsync-flush", "no-eot-packet", "clock-non-continuous", "lpm",
+};
+
+static void mipi_dsi_list(bool verbose)
+{
+	struct mipi_dsi_device *dsi;
+	struct device *dev;
+
+	bus_for_each_device(&mipi_dsi_bus_type, dev) {
+		const char *format = "unknown";
+
+		dsi = to_mipi_dsi_device(dev);
+		printf("%s%s", dev_name(dev),
+		       dsi->attached ? "" : " (not attached)");
+
+		if (dsi->format < ARRAY_SIZE(mipi_dsi_formats))
+			format = mipi_dsi_formats[dsi->format];
+
+		if (verbose) {
+			printf(": host %s, channel %u, %u lanes, %s, flags",
+			       dev_name(dsi->host->dev), dsi->channel,
+			       dsi->lanes, format);
+
+			for (int i = 0; i < ARRAY_SIZE(mipi_dsi_mode_flags); i++) {
+				if (dsi->mode_flags & BIT(i))
+					printf(" %s", mipi_dsi_mode_flags[i]);
+			}
+		}
+
+		printf("\n");
+	}
+}
+
+struct mipi_dsi_opts {
+	bool write, info, generic;
+	int peripheral;	/* 1: turn on, 0: shut down, -1: none */
+	unsigned int len;	/* 0: the known length of the register or 1 */
+};
+
+static int mipi_dsi_execute(struct mipi_dsi_device *dsi,
+			    const struct mipi_dsi_opts *opts,
+			    int argc, char *argv[])
+{
+	u8 buf[MIPI_DSI_CMD_MAX_LEN];
+	unsigned int len;
+	int ret, i;
+
+	if (opts->peripheral >= 0) {
+		if (opts->write || opts->info || opts->generic || argc)
+			return COMMAND_ERROR_USAGE;
+		if (opts->peripheral)
+			return mipi_dsi_turn_on_peripheral(dsi);
+		return mipi_dsi_shutdown_peripheral(dsi);
+	}
+
+	if (opts->info) {
+		if (opts->write || opts->generic || argc)
+			return COMMAND_ERROR_USAGE;
+		return mipi_dsi_command_show_list(dsi, dcs_ids,
+						  ARRAY_SIZE(dcs_ids));
+	}
+
+	if (!argc) {
+		if (opts->write || opts->generic)
+			return COMMAND_ERROR_USAGE;
+		return mipi_dsi_command_show_list(dsi, dcs_reads,
+						  ARRAY_SIZE(dcs_reads));
+	}
+
+	if (argc > sizeof(buf)) {
+		printf("can only send up to %zu bytes at once\n", sizeof(buf));
+		return -EOVERFLOW;
+	}
+
+	for (i = 0; i < argc; i++) {
+		ret = kstrtou8(argv[i], 16, &buf[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (opts->write) {
+		if (opts->generic)
+			ret = mipi_dsi_generic_write(dsi, buf, argc);
+		else
+			ret = mipi_dsi_dcs_write_buffer(dsi, buf, argc);
+		return ret < 0 ? ret : 0;
+	}
+
+	if (argc > (opts->generic ? 2 : 1))
+		return COMMAND_ERROR_USAGE;
+
+	len = opts->len;
+	if (!len)
+		len = opts->generic ? 1 : dcs_read_len(buf[0]);
+
+	return mipi_dsi_command_show(dsi, opts->generic, buf, argc, len,
+				     false);
+}
+
+static int do_mipi_dsi(int argc, char *argv[])
+{
+	struct mipi_dsi_opts opts = { .peripheral = -1 };
+	struct mipi_dsi_device *dsi;
+	struct device *dev;
+	bool list = false, verbose = false, lpm = false, hs = false;
+	unsigned long mode_flags;
+	unsigned int channel, vc = UINT_MAX;
+	int opt, ret;
+
+	dev = list_first_entry_or_null(&mipi_dsi_bus_type.device_list,
+				       struct device, bus_list);
+
+	while ((opt = getopt(argc, argv, "c:d:gHilLn:p:vw")) > 0) {
+		switch (opt) {
+		case 'c':
+			ret = kstrtouint(optarg, 0, &vc);
+			if (ret)
+				return ret;
+			if (vc > 3)
+				return -EINVAL;
+			break;
+		case 'd':
+			dev = bus_find_device(&mipi_dsi_bus_type, NULL,
+					      optarg, device_match_name);
+			break;
+		case 'g':
+			opts.generic = true;
+			break;
+		case 'H':
+			hs = true;
+			break;
+		case 'i':
+			opts.info = true;
+			break;
+		case 'l':
+			list = true;
+			break;
+		case 'L':
+			lpm = true;
+			break;
+		case 'n':
+			ret = kstrtouint(optarg, 0, &opts.len);
+			if (ret)
+				return ret;
+			if (!opts.len || opts.len > MIPI_DSI_CMD_MAX_LEN)
+				return -EINVAL;
+			break;
+		case 'p':
+			if (!strcmp(optarg, "on"))
+				opts.peripheral = 1;
+			else if (!strcmp(optarg, "off"))
+				opts.peripheral = 0;
+			else
+				return COMMAND_ERROR_USAGE;
+			break;
+		case 'v':
+			verbose = true;
+			break;
+		case 'w':
+			opts.write = true;
+			break;
+		default:
+			return COMMAND_ERROR_USAGE;
+		}
+	}
+
+	if (list || verbose) {
+		mipi_dsi_list(verbose);
+		return 0;
+	}
+
+	if (lpm && hs)
+		return COMMAND_ERROR_USAGE;
+
+	if (!dev)
+		return -ENODEV;
+
+	dsi = to_mipi_dsi_device(dev);
+	if (!dsi->attached) {
+		printf("%s: not attached to its DSI host\n", dev_name(dev));
+		return -ENODEV;
+	}
+
+	mode_flags = dsi->mode_flags;
+	channel = dsi->channel;
+	if (lpm)
+		dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+	if (hs)
+		dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+	if (vc != UINT_MAX)
+		dsi->channel = vc;
+
+	ret = mipi_dsi_execute(dsi, &opts, argc - optind, argv + optind);
+
+	dsi->mode_flags = mode_flags;
+	dsi->channel = channel;
+
+	if (ret == -ENETDOWN)
+		printf("DSI host is powered down, enable the display first\n");
+
+	return ret;
+}
+
+BAREBOX_CMD_HELP_START(mipi_dsi)
+BAREBOX_CMD_HELP_TEXT("Without CMD, dump the standard DCS registers.")
+BAREBOX_CMD_HELP_TEXT("CMD and DATA bytes are given in hex.")
+BAREBOX_CMD_HELP_TEXT("")
+BAREBOX_CMD_HELP_TEXT("Options:")
+BAREBOX_CMD_HELP_OPT ("-l\t",  "list all MIPI DSI devices")
+BAREBOX_CMD_HELP_OPT ("-v\t",  "list with host, channel, lanes, format and mode flags")
+BAREBOX_CMD_HELP_OPT ("-d DEVICE",  "select specific device (default is first registered)")
+BAREBOX_CMD_HELP_OPT ("-i\t",  "read the panel identification registers")
+BAREBOX_CMD_HELP_OPT ("-n LEN\t",  "number of bytes to read (default: known length, else 1)")
+BAREBOX_CMD_HELP_OPT ("-w\t",  "issue write command")
+BAREBOX_CMD_HELP_OPT ("-g\t",  "send generic packets: CMD and DATA are the payload,")
+BAREBOX_CMD_HELP_OPT ("\t",  "reads take up to two bytes")
+BAREBOX_CMD_HELP_OPT ("-p on|off",  "send Turn On or Shutdown Peripheral")
+BAREBOX_CMD_HELP_OPT ("-c CH\t",  "use virtual channel CH (0-3)")
+BAREBOX_CMD_HELP_OPT ("-L\t",  "send in low power mode")
+BAREBOX_CMD_HELP_OPT ("-H\t",  "send in high speed mode")
+BAREBOX_CMD_HELP_END
+
+BAREBOX_CMD_START(mipi_dsi)
+	.cmd		= do_mipi_dsi,
+	BAREBOX_CMD_DESC("interact with MIPI DSI device")
+	BAREBOX_CMD_OPTS("[-lvdinwgLH] [-c CH] [-p on|off] [CMD] [DATA...]")
+	BAREBOX_CMD_GROUP(CMD_GRP_HWMANIP)
+	BAREBOX_CMD_HELP(cmd_mipi_dsi_help)
+BAREBOX_CMD_END
diff --git a/test/py/test_mipi_dsi.py b/test/py/test_mipi_dsi.py
new file mode 100644
index 000000000000..b66cf256de3a
--- /dev/null
+++ b/test/py/test_mipi_dsi.py
@@ -0,0 +1,78 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+import pytest
+from .helper import skip_disabled
+
+DISPLAY_ON = 1 << 2
+
+
+@pytest.fixture(autouse=True)
+def mipi_dsi(barebox, barebox_config):
+    skip_disabled(barebox_config, "CONFIG_CMD_MIPI_DSI")
+
+    devices = barebox.run_check("mipi_dsi -l")
+    if not any(d and "not attached" not in d for d in devices):
+        pytest.skip("no attached MIPI DSI device")
+
+    _, _, ret = barebox.run("test -e /dev/fb0")
+    if ret != 0:
+        pytest.skip("no framebuffer to enable the DSI link")
+
+    barebox.run_check("fb0.enable=1")
+    yield
+    barebox.run_check("fb0.enable=1")
+
+
+def power_mode(barebox):
+    out = barebox.run_check("mipi_dsi 0a")
+    return int(out[-1], 16)
+
+
+def test_mipi_dsi_identify(barebox):
+    out = barebox.run_check("mipi_dsi -i")
+    assert any(line.startswith("04: ") and len(line) == 10 for line in out)
+
+
+def test_mipi_dsi_read_len(barebox):
+    assert len(barebox.run_check("mipi_dsi 04")[-1]) == 6
+    assert len(barebox.run_check("mipi_dsi -n 1 04")[-1]) == 2
+
+
+def test_mipi_dsi_dump(barebox):
+    out = barebox.run_check("mipi_dsi")
+    assert any(line.startswith("0a: ") for line in out)
+
+
+def test_mipi_dsi_list_verbose(barebox):
+    out = barebox.run_check("mipi_dsi -l -v")
+    assert any(" lanes, " in line for line in out)
+
+
+@pytest.mark.parametrize("opts", ["", "-g", "-L", "-H"])
+def test_mipi_dsi_display_off_on(barebox, opts):
+    assert power_mode(barebox) & DISPLAY_ON
+
+    barebox.run_check(f"mipi_dsi {opts} -w 28")
+    assert not power_mode(barebox) & DISPLAY_ON
+
+    barebox.run_check(f"mipi_dsi {opts} -w 29")
+    assert power_mode(barebox) & DISPLAY_ON
+
+
+def test_mipi_dsi_channel(barebox):
+    barebox.run_check("mipi_dsi -c 0 0a")
+
+    _, _, ret = barebox.run("mipi_dsi -c 1 0a")
+    assert ret != 0
+
+
+def test_mipi_dsi_peripheral(barebox):
+    barebox.run_check("mipi_dsi -p on")
+
+
+def test_mipi_dsi_powered_down(barebox):
+    barebox.run_check("fb0.enable=0")
+
+    out, _, ret = barebox.run("mipi_dsi -w 29")
+    assert ret != 0
+    assert "DSI host is powered down" in "\n".join(out)
-- 
2.47.3