[PATCH v3 2/2] drm:bridge: Add Lontiun LT7911EXC eDP to MIPI DSI bridge

syyang
2026-04-29T04:05:56Z

and output signal/dual port mipi.

Signed-off-by: Sunyun Yang <syyang@lontium.com>
---
drivers/gpu/drm/bridge/Kconfig | 13 +
drivers/gpu/drm/bridge/Makefile | 1 +
drivers/gpu/drm/bridge/lontium-lt7911exc.c | 493 +++++++++++++++++++++
3 files changed, 507 insertions(+)
create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index c3209b0f4678..8cff2bf15b09 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -132,6 +132,19 @@ config DRM_ITE_IT6505
help
ITE IT6505 DisplayPort bridge chip driver.

+config DRM_LONTIUM_LT7911EXC
+ tristate "Lontium eDP/MIPI bridge"
+ depends on OF
+ select CRC32
+ select FW_LOADER
+ select DRM_PANEL
+ select DRM_KMS_HELPER
+ help
+ DRM driver for the Lontium LT7911EXC bridge chip.
+ The LT7911EXC converts eDP input to single/dual port
+ MIPI DSI output.
+ Please say Y if you have such hardware.
+
config DRM_LONTIUM_LT8912B
tristate "Lontium LT8912B DSI/HDMI bridge"
depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index beab5b695a6e..70ddca75dd3a 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_DRM_I2C_NXP_TDA998X) += tda998x.o
obj-$(CONFIG_DRM_INNO_HDMI) += inno-hdmi.o
obj-$(CONFIG_DRM_ITE_IT6263) += ite-it6263.o
obj-$(CONFIG_DRM_ITE_IT6505) += ite-it6505.o
+obj-$(CONFIG_DRM_LONTIUM_LT7911EXC) += lontium-lt7911exc.o
obj-$(CONFIG_DRM_LONTIUM_LT8912B) += lontium-lt8912b.o
obj-$(CONFIG_DRM_LONTIUM_LT9211) += lontium-lt9211.o
obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
diff --git a/drivers/gpu/drm/bridge/lontium-lt7911exc.c b/drivers/gpu/drm/bridge/lontium-lt7911exc.c
new file mode 100644
index 000000000000..02648b396343
--- /dev/null
+++ b/drivers/gpu/drm/bridge/lontium-lt7911exc.c
@@ -0,0 +1,493 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2026 Lontium Semiconductor, Inc.
+ */
+
+#include <linux/crc32.h>
+#include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_graph.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_bridge.h>
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.h>
+
+#define FW_SIZE (64 * 1024)
+#define LT_PAGE_SIZE 32
+#define FW_FILE "lt7911exc_fw.bin"
+#define LT7911EXC_PAGE_CONTROL 0xff
+
+struct lt7911exc {
+ struct device *dev;
+ struct i2c_client *client;
+ struct drm_bridge bridge;
+ struct regmap *regmap;
+ /* Protects all accesses to registers by stopping the on-chip MCU */
+ struct mutex ocm_lock;
+ struct regulator_bulk_data supplies[2];
+ struct gpio_desc *reset_gpio;
+ int fw_version;
+};
+
+static const struct regmap_range_cfg lt7911exc_ranges[] = {
+ {
+ .name = "register_range",
+ .range_min = 0,
+ .range_max = 0xe8ff,
+ .selector_reg = LT7911EXC_PAGE_CONTROL,
+ .selector_mask = 0xff,
+ .selector_shift = 0,
+ .window_start = 0,
+ .window_len = 0x100,
+ },
+};
+
+static const struct regmap_config lt7911exc_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = 0xe8ff,
+ .ranges = lt7911exc_ranges,
+ .num_ranges = ARRAY_SIZE(lt7911exc_ranges),
+};
+
+static u32 cal_crc32_custom(const u8 *data, u64 length)
+{
+ u32 crc = 0xffffffff;
+ u8 buf[4];
+ u64 i;
+
+ for (i = 0; i < length; i += 4) {
+ buf[0] = data[i + 3];
+ buf[1] = data[i + 2];
+ buf[2] = data[i + 1];
+ buf[3] = data[i + 0];
+ crc = crc32_be(crc, buf, 4);
+ }
+
+ return crc;
+}
+
+static inline struct lt7911exc *bridge_to_lt7911exc(struct drm_bridge *bridge)
+{
+ return container_of(bridge, struct lt7911exc, bridge);
+}
+
+static void lt7911exc_reset(struct lt7911exc *lt7911exc)
+{
+ gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+ msleep(20);
+
+ gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+ msleep(20);
+
+ gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+ msleep(400);
+
+ dev_dbg(lt7911exc->dev, "lt7911exc reset.\n");
+}
+
+static int lt7911exc_parse_dt(struct lt7911exc *lt7911exc)
+{
+ struct device *dev = lt7911exc->dev;
+ int ret;
+
+ lt7911exc->supplies[0].supply = "vcc";
+ lt7911exc->supplies[1].supply = "vdd";
+
+ ret = devm_regulator_bulk_get(dev, 2, lt7911exc->supplies);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed get regulator\n");
+
+ lt7911exc->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+ if (IS_ERR(lt7911exc->reset_gpio))
+ return dev_err_probe(dev, PTR_ERR(lt7911exc->reset_gpio),
+ "failed to acquire reset gpio\n");
+
+ return 0;
+}
+
+static int lt7911exc_read_version(struct lt7911exc *lt7911exc)
+{
+ u8 buf[3];
+ int ret;
+
+ ret = regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+ if (ret)
+ return ret;
+ ret = regmap_bulk_read(lt7911exc->regmap, 0xe081, buf, sizeof(buf));
+ if (ret)
+ return ret;
+
+ return (buf[0] << 16) | (buf[1] << 8) | buf[2];
+}
+
+static void lt7911exc_lock(struct lt7911exc *lt7911exc)
+{
+ mutex_lock(&lt7911exc->ocm_lock);
+ regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+}
+
+static void lt7911exc_unlock(struct lt7911exc *lt7911exc)
+{
+ regmap_write(lt7911exc->regmap, 0xe0ee, 0x00);
+ mutex_unlock(&lt7911exc->ocm_lock);
+}
+
+static void lt7911exc_block_erase(struct lt7911exc *lt7911exc)
+{
+ struct device *dev = lt7911exc->dev;
+ const u32 addr = 0x00;
+
+ const struct reg_sequence seq_write[] = {
+ REG_SEQ0(0xe0ee, 0x01),
+ REG_SEQ0(0xe054, 0x01),
+ REG_SEQ0(0xe055, 0x06),
+ REG_SEQ0(0xe051, 0x01),
+ REG_SEQ0(0xe051, 0x00),
+ REG_SEQ0(0xe054, 0x05),
+ REG_SEQ0(0xe055, 0xd8),
+ REG_SEQ0(0xe05a, (addr >> 16) & 0xff),
+ REG_SEQ0(0xe05b, (addr >> 8) & 0xff),
+ REG_SEQ0(0xe05c, addr & 0xff),
+ REG_SEQ0(0xe051, 0x01),
+ REG_SEQ0(0xe050, 0x00),
+ };
+
+ regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+
+ msleep(200);
+ dev_dbg(dev, "erase flash done.\n");
+}
+
+static void lt7911exc_prog_init(struct lt7911exc *lt7911exc, u64 addr)
+{
+ const struct reg_sequence seq_write[] = {
+ REG_SEQ0(0xe0ee, 0x01),
+ REG_SEQ0(0xe05f, 0x01),
+ REG_SEQ0(0xe05a, (addr >> 16) & 0xff),
+ REG_SEQ0(0xe05b, (addr >> 8) & 0xff),
+ REG_SEQ0(0xe05c, addr & 0xff),
+ };
+
+ regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+}
+
+static int lt7911exc_write_data(struct lt7911exc *lt7911exc, const struct firmware *fw, u64 addr)
+{
+ struct device *dev = lt7911exc->dev;
+ int ret;
+ int page = 0, num = 0, page_len = 0;
+ u64 size, offset;
+ const u8 *data;
+
+ data = fw->data;
+ size = fw->size;
+ page = (size + LT_PAGE_SIZE - 1) / LT_PAGE_SIZE;
+ if (page * LT_PAGE_SIZE > FW_SIZE) {
+ dev_err(dev, "firmware size out of range\n");
+ return -EINVAL;
+ }
+
+ dev_dbg(dev, "%u pages, total size %llu byte\n", page, size);
+
+ for (num = 0; num < page; num++) {
+ offset = num * LT_PAGE_SIZE;
+ page_len = (offset + LT_PAGE_SIZE <= size) ? LT_PAGE_SIZE : (size - offset);
+ lt7911exc_prog_init(lt7911exc, addr);
+
+ ret = regmap_raw_write(lt7911exc->regmap, 0xe05d, &data[offset], page_len);
+ if (ret) {
+ dev_err(dev, "write error at page %d\n", num);
+ return ret;
+ }
+
+ if (page_len < LT_PAGE_SIZE) {
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x05);
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+ //hardware requires delay
+ usleep_range(1000, 2000);
+ }
+
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x00);
+ addr += LT_PAGE_SIZE;
+ }
+
+ return 0;
+}
+
+static int lt7911exc_write_crc(struct lt7911exc *lt7911exc, u32 crc32, u64 addr)
+{
+ u8 crc[4];
+ int ret;
+
+ crc[0] = crc32 & 0xff;
+ crc[1] = (crc32 >> 8) & 0xff;
+ crc[2] = (crc32 >> 16) & 0xff;
+ crc[3] = (crc32 >> 24) & 0xff;
+
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+ regmap_write(lt7911exc->regmap, 0xe05a, (addr >> 16) & 0xff);
+ regmap_write(lt7911exc->regmap, 0xe05b, (addr >> 8) & 0xff);
+ regmap_write(lt7911exc->regmap, 0xe05c, addr & 0xff);
+
+ ret = regmap_raw_write(lt7911exc->regmap, 0xe05d, crc, 4);
+ if (ret)
+ return ret;
+
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x05);
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+ usleep_range(1000, 2000);
+ regmap_write(lt7911exc->regmap, 0xe05f, 0x00);
+
+ return 0;
+}
+
+static int lt7911exc_upgrade_result(struct lt7911exc *lt7911exc, u32 crc32)
+{
+ struct device *dev = lt7911exc->dev;
+ u32 read_hw_crc = 0;
+ u8 crc_tmp[4];
+ int ret;
+
+ regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+ regmap_write(lt7911exc->regmap, 0xe07b, 0x60);
+ regmap_write(lt7911exc->regmap, 0xe07b, 0x40);
+ msleep(150);
+ ret = regmap_bulk_read(lt7911exc->regmap, 0x22, crc_tmp, 4);
+ if (ret) {
+ dev_err(lt7911exc->dev, "Failed to read CRC: %d\n", ret);
+ return ret;
+ }
+
+ read_hw_crc = crc_tmp[0] << 24 | crc_tmp[1] << 16 |
+ crc_tmp[2] << 8 | crc_tmp[3];
+
+ if (read_hw_crc != crc32) {
+ dev_err(dev, "lt7911exc firmware upgrade failed, expected CRC=0x%08x, read CRC=0x%08x\n",
+ crc32, read_hw_crc);
+ return -EIO;
+ }
+
+ dev_dbg(dev, "lt7911exc firmware upgrade success, CRC=0x%08x\n", read_hw_crc);
+ return 0;
+}
+
+static int lt7911exc_firmware_upgrade(struct lt7911exc *lt7911exc)
+{
+ struct device *dev = lt7911exc->dev;
+ const struct firmware *fw;
+ u8 *buffer;
+ size_t total_size = FW_SIZE - 4;
+ u32 crc32;
+ int ret;
+
+ /*1. load firmware*/
+ ret = request_firmware(&fw, FW_FILE, dev);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to load '%s'\n", FW_FILE);
+
+ /*2. check size*/
+ if (fw->size > total_size) {
+ dev_err(dev, "firmware too large (%zu > %zu)\n", fw->size, total_size);
+ ret = -EINVAL;
+ goto out_release_fw;
+ }
+
+ /*3. calculate crc32 */
+ buffer = kzalloc(total_size, GFP_KERNEL);
+ if (!buffer) {
+ ret = -ENOMEM;
+ goto out_release_fw;
+ }
+ memset(buffer, 0xff, total_size);
+ memcpy(buffer, fw->data, fw->size);
+
+ crc32 = cal_crc32_custom(buffer, total_size);
+ kfree(buffer);
+
+ /*4. firmware upgrade */
+ dev_dbg(dev, "starting firmware upgrade, size: %zu bytes\n", fw->size);
+
+ lt7911exc_block_erase(lt7911exc);
+
+ ret = lt7911exc_write_data(lt7911exc, fw, 0);
+ if (ret < 0) {
+ dev_err(dev, "failed to write firmware data\n");
+ goto out_release_fw;
+ }
+
+ ret = lt7911exc_write_crc(lt7911exc, crc32, FW_SIZE - 4);
+ if (ret < 0) {
+ dev_err(dev, "failed to write firmware crc\n");
+ goto out_release_fw;
+ }
+
+ /*5. check upgrade of result*/
+ lt7911exc_reset(lt7911exc);
+
+ ret = lt7911exc_upgrade_result(lt7911exc, crc32);
+
+out_release_fw:
+ release_firmware(fw);
+ return ret;
+}
+
+static void lt7911exc_atomic_pre_enable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+ struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+ int ret;
+
+ ret = regulator_bulk_enable(ARRAY_SIZE(lt7911exc->supplies), lt7911exc->supplies);
+ if (ret)
+ return;
+
+ lt7911exc_reset(lt7911exc);
+}
+
+static void lt7911exc_atomic_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+ /* Delay after panel is disabled */
+ msleep(20);
+}
+
+static void lt7911exc_atomic_post_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+ struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+ int ret;
+
+ ret = regulator_bulk_disable(ARRAY_SIZE(lt7911exc->supplies), lt7911exc->supplies);
+ if (ret)
+ return;
+
+ gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+}
+
+static int lt7911exc_attach(struct drm_bridge *bridge,
+ struct drm_encoder *encoder,
+ enum drm_bridge_attach_flags flags)
+{
+ struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+ return drm_bridge_attach(lt7911exc->bridge.encoder, lt7911exc->bridge.next_bridge,
+ &lt7911exc->bridge, flags);
+}
+
+static const struct drm_bridge_funcs lt7911exc_bridge_funcs = {
+ .attach = lt7911exc_attach,
+ .atomic_pre_enable = lt7911exc_atomic_pre_enable,
+ .atomic_disable = lt7911exc_atomic_disable,
+ .atomic_post_disable = lt7911exc_atomic_post_disable,
+};
+
+static int lt7911exc_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct lt7911exc *lt7911exc;
+ bool fw_updated = false;
+ int ret;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+ dev_err(dev, "device doesn't support I2C\n");
+ return -ENODEV;
+ }
+
+ lt7911exc = devm_drm_bridge_alloc(dev, struct lt7911exc, bridge,
+ &lt7911exc_bridge_funcs);
+ if (IS_ERR(lt7911exc))
+ return dev_err_probe(dev, PTR_ERR(lt7911exc), "drm bridge alloc failed.\n");
+
+ lt7911exc->bridge.next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
+ if (IS_ERR(lt7911exc->bridge.next_bridge))
+ return PTR_ERR(lt7911exc->bridge.next_bridge);
+
+ lt7911exc->client = client;
+ lt7911exc->dev = dev;
+ i2c_set_clientdata(client, lt7911exc);
+
+ ret = devm_mutex_init(dev, &lt7911exc->ocm_lock);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to init mutex\n");
+
+ lt7911exc->regmap = devm_regmap_init_i2c(client, &lt7911exc_regmap_config);
+ if (IS_ERR(lt7911exc->regmap))
+ return dev_err_probe(dev, PTR_ERR(lt7911exc->regmap), "regmap i2c init failed\n");
+
+ ret = lt7911exc_parse_dt(lt7911exc);
+ if (ret)
+ return ret;
+
+ ret = regulator_bulk_enable(ARRAY_SIZE(lt7911exc->supplies), lt7911exc->supplies);
+ if (ret)
+ return ret;
+
+ lt7911exc_reset(lt7911exc);
+ lt7911exc_lock(lt7911exc);
+
+retry:
+ lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
+ if (lt7911exc->fw_version < 0) {
+ dev_err(dev, "failed to read chip fw version\n");
+ ret = -EOPNOTSUPP;
+ goto err_disable_regulators;
+
+ } else if (lt7911exc->fw_version == 0) {
+ if (!fw_updated) {
+ fw_updated = true;
+ ret = lt7911exc_firmware_upgrade(lt7911exc);
+ if (ret < 0)
+ goto err_disable_regulators;
+
+ goto retry;
+
+ } else {
+ dev_err(dev, "fw version 0x%04x, update failed\n", lt7911exc->fw_version);
+ ret = -EOPNOTSUPP;
+ goto err_disable_regulators;
+ }
+ }
+
+ lt7911exc_unlock(lt7911exc);
+
+ lt7911exc->bridge.of_node = dev->of_node;
+ devm_drm_bridge_add(dev, &lt7911exc->bridge);
+
+ return 0;
+
+err_disable_regulators:
+ lt7911exc_unlock(lt7911exc);
+ regulator_bulk_disable(ARRAY_SIZE(lt7911exc->supplies), lt7911exc->supplies);
+ return ret;
+}
+
+static const struct i2c_device_id lt7911exc_i2c_table[] = {
+ {"lt7911exc"},
+ {/* sentinel */}
+};
+
+MODULE_DEVICE_TABLE(i2c, lt7911exc_i2c_table);
+
+static const struct of_device_id lt7911exc_devices[] = {
+ {.compatible = "lontium,lt7911exc"},
+ {/* sentinel */}
+};
+MODULE_DEVICE_TABLE(of, lt7911exc_devices);
+
+static struct i2c_driver lt7911exc_driver = {
+ .id_table = lt7911exc_i2c_table,
+ .probe = lt7911exc_probe,
+ .driver = {
+ .name = "lt7911exc",
+ .of_match_table = lt7911exc_devices,
+ },
+};
+module_i2c_driver(lt7911exc_driver);
+
+MODULE_AUTHOR("SunYun Yang <syyang@lontium.com>");
+MODULE_DESCRIPTION("Lontium LT7911EXC EDP to MIPI DSI bridge driver");
+MODULE_LICENSE("GPL");
+MODULE_FIRMWARE(FW_FILE);
--
2.34.1