* [PATCH v4 2/4] i2c: add Andes I2C driver support
2026-03-30 7:30 [PATCH v4 0/4] i2c: add support for Andes platform Ben Zong-You Xie via B4 Relay
2026-03-30 7:30 ` [PATCH v4 1/4] dt-bindings: i2c: add support for AE350 I2C controller Ben Zong-You Xie via B4 Relay
@ 2026-03-30 7:30 ` Ben Zong-You Xie via B4 Relay
2026-03-30 7:30 ` [PATCH v4 3/4] MAINTAINERS: add an entry for Andes I2C driver Ben Zong-You Xie via B4 Relay
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Ben Zong-You Xie via B4 Relay @ 2026-03-30 7:30 UTC (permalink / raw)
To: Andi Shyti, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Paul Walmsley, Palmer Dabbelt, Albert Ou, Alexandre Ghiti
Cc: linux-i2c, devicetree, linux-kernel, linux-riscv,
Ben Zong-You Xie
From: Ben Zong-You Xie <ben717@andestech.com>
Add support for Andes I2C driver. Andes I2C can act as either a
controller or a target, depending on the control register settings. Now,
we only support controller mode.
Signed-off-by: Ben Zong-You Xie <ben717@andestech.com>
---
drivers/i2c/busses/Kconfig | 10 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-andes.c | 341 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 352 insertions(+)
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 7cb6b9b864a7..6aaa5a1223c2 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -446,6 +446,16 @@ config I2C_AT91_SLAVE_EXPERIMENTAL
- There are some mismatches with a SAMA5D4 as slave and a SAMA5D2 as
master.
+config I2C_ANDES
+ tristate "Andes I2C Controller"
+ depends on ARCH_ANDES || COMPILE_TEST
+ help
+ If you say yes to this option, support will be included for the
+ Andes I2C controller.
+
+ This support is also available as a module. If so, the module
+ will be called i2c-andes.
+
config I2C_AU1550
tristate "Au1550/Au1200/Au1300 SMBus interface"
depends on MIPS_ALCHEMY
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 547123ab351f..89d85d10f8d2 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_I2C_ASPEED) += i2c-aspeed.o
obj-$(CONFIG_I2C_AT91) += i2c-at91.o
i2c-at91-y := i2c-at91-core.o i2c-at91-master.o
i2c-at91-$(CONFIG_I2C_AT91_SLAVE_EXPERIMENTAL) += i2c-at91-slave.o
+obj-$(CONFIG_I2C_ANDES) += i2c-andes.o
obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o
obj-$(CONFIG_I2C_AXXIA) += i2c-axxia.o
obj-$(CONFIG_I2C_BCM2835) += i2c-bcm2835.o
diff --git a/drivers/i2c/busses/i2c-andes.c b/drivers/i2c/busses/i2c-andes.c
new file mode 100644
index 000000000000..5f135d8c9b13
--- /dev/null
+++ b/drivers/i2c/busses/i2c-andes.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Andes I2C controller, used in Andes AE350 platform and QiLai SoC
+ *
+ * Copyright (C) 2026 Andes Technology Corporation.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/completion.h>
+#include <linux/iopoll.h>
+#include <linux/i2c.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/spinlock.h>
+
+#define ANDES_I2C_ID_REG 0x0
+#define ANDES_I2C_ID_MASK GENMASK(31, 8)
+#define ANDES_I2C_ID 0x020210
+
+#define ANDES_I2C_CFG_REG 0x10
+#define ANDES_I2C_CFG_FIFOSIZE GENMASK(1, 0)
+
+#define ANDES_I2C_INTEN_REG 0x14
+#define ANDES_I2C_INTEN_FIFO_EMPTY BIT(0)
+#define ANDES_I2C_INTEN_FIFO_FULL BIT(1)
+#define ANDES_I2C_INTEN_CMPL BIT(9)
+
+#define ANDES_I2C_STATUS_REG 0x18
+#define ANDES_I2C_STATUS_FIFO_EMPTY BIT(0)
+#define ANDES_I2C_STATUS_FIFO_FULL BIT(1)
+#define ANDES_I2C_STATUS_ADDR_HIT BIT(3)
+#define ANDES_I2C_STATUS_CMPL BIT(9)
+#define ANDES_I2C_STATUS_W1C GENMASK(9, 3)
+
+#define ANDES_I2C_ADDR_REG 0x1C
+
+#define ANDES_I2C_DATA_REG 0x20
+
+#define ANDES_I2C_CTRL_REG 0x24
+#define ANDES_I2C_CTRL_DATA_CNT GENMASK(7, 0)
+#define ANDES_I2C_CTRL_DIR BIT(8)
+#define ANDES_I2C_CTRL_PHASE GENMASK(12, 9)
+
+#define ANDES_I2C_CMD_REG 0x28
+#define ANDES_I2C_CMD_ACTION GENMASK(2, 0)
+#define ANDES_I2C_CMD_TRANS BIT(0)
+
+#define ANDES_I2C_SETUP_REG 0x2C
+#define ANDES_I2C_SETUP_IICEN BIT(0)
+#define ANDES_I2C_SETUP_REQ BIT(2)
+
+#define ANDES_I2C_TPM_REG 0x30
+
+#define ANDES_I2C_TIMEOUT_US 400000
+#define ANDES_I2C_TIMEOUT usecs_to_jiffies(ANDES_I2C_TIMEOUT_US)
+
+#define ANDES_I2C_MAX_DATA_LEN 256
+
+struct andes_i2c {
+ struct i2c_adapter adap;
+ struct completion completion;
+ spinlock_t lock;
+ struct regmap *map;
+ u8 *buf;
+ unsigned int fifo_size;
+ int irq;
+ u16 buf_len;
+ bool addr_hit;
+ bool xfer_done;
+};
+
+static const struct regmap_config andes_i2c_regmap_config = {
+ .name = "andes_i2c",
+ .reg_bits = 32,
+ .reg_stride = 4,
+ .val_bits = 32,
+ .pad_bits = 0,
+ .max_register = ANDES_I2C_TPM_REG,
+ .cache_type = REGCACHE_NONE,
+};
+
+static void andes_i2c_xfer_common(struct andes_i2c *i2c, u32 status)
+{
+ unsigned long flags;
+ unsigned int fsize = i2c->fifo_size;
+ unsigned int val;
+
+ spin_lock_irqsave(&i2c->lock, flags);
+ if (status & ANDES_I2C_STATUS_FIFO_EMPTY) {
+ /* Disable the FIFO empty interrupt for the last write */
+ if (i2c->buf_len <= fsize) {
+ fsize = i2c->buf_len;
+ regmap_clear_bits(i2c->map, ANDES_I2C_INTEN_REG,
+ ANDES_I2C_INTEN_FIFO_EMPTY);
+ }
+
+ while (fsize--) {
+ val = *i2c->buf++;
+ regmap_write(i2c->map, ANDES_I2C_DATA_REG, val);
+ i2c->buf_len--;
+ }
+ } else if (status & ANDES_I2C_STATUS_FIFO_FULL) {
+ while (fsize--) {
+ regmap_read(i2c->map, ANDES_I2C_DATA_REG, &val);
+ *i2c->buf++ = (u8)val;
+ i2c->buf_len--;
+ }
+ }
+
+ if (status & ANDES_I2C_STATUS_CMPL) {
+ i2c->xfer_done = true;
+ if (status & ANDES_I2C_STATUS_ADDR_HIT)
+ i2c->addr_hit = true;
+
+ /* Write 1 to clear the status */
+ regmap_set_bits(i2c->map, ANDES_I2C_STATUS_REG,
+ ANDES_I2C_STATUS_W1C);
+
+ /* For the last read, retrieve all remaining data in FIFO. */
+ while (i2c->buf_len > 0) {
+ regmap_read(i2c->map, ANDES_I2C_DATA_REG, &val);
+ *i2c->buf++ = (u8)val;
+ i2c->buf_len--;
+ }
+ }
+
+ spin_unlock_irqrestore(&i2c->lock, flags);
+}
+
+static irqreturn_t andes_i2c_irq_handler(int irq, void *data)
+{
+ struct andes_i2c *i2c = data;
+ u32 i2c_status;
+
+ regmap_read(i2c->map, ANDES_I2C_STATUS_REG, &i2c_status);
+ andes_i2c_xfer_common(i2c, i2c_status);
+ if (i2c->xfer_done)
+ complete(&i2c->completion);
+
+ return IRQ_HANDLED;
+}
+
+static int andes_i2c_xfer_wait(struct andes_i2c *i2c, struct i2c_msg *msg)
+{
+ unsigned int mask;
+ unsigned int i2c_ctrl;
+
+ /*
+ * Set the data count. If there are 256 bytes to be transmitted, write
+ * zero to the data count field.
+ */
+ regmap_update_bits(i2c->map, ANDES_I2C_CTRL_REG,
+ ANDES_I2C_CTRL_DATA_CNT,
+ FIELD_PREP(ANDES_I2C_CTRL_DATA_CNT, i2c->buf_len));
+
+ regmap_set_bits(i2c->map, ANDES_I2C_CTRL_REG, ANDES_I2C_CTRL_PHASE);
+ if (msg->flags & I2C_M_RD)
+ regmap_set_bits(i2c->map, ANDES_I2C_CTRL_REG,
+ ANDES_I2C_CTRL_DIR);
+ else
+ regmap_clear_bits(i2c->map, ANDES_I2C_CTRL_REG,
+ ANDES_I2C_CTRL_DIR);
+
+ regmap_write(i2c->map, ANDES_I2C_ADDR_REG, msg->addr);
+
+ if (i2c->irq >= 0) {
+ mask = ANDES_I2C_INTEN_CMPL;
+ mask |= (msg->flags & I2C_M_RD) ? ANDES_I2C_INTEN_FIFO_FULL
+ : ANDES_I2C_INTEN_FIFO_EMPTY;
+ regmap_set_bits(i2c->map, ANDES_I2C_INTEN_REG, mask);
+ }
+
+ regmap_set_bits(i2c->map, ANDES_I2C_CMD_REG, ANDES_I2C_CMD_TRANS);
+ if (i2c->irq >= 0) {
+ unsigned long time_left;
+
+ time_left = wait_for_completion_timeout(&i2c->completion,
+ ANDES_I2C_TIMEOUT);
+ if (!time_left)
+ return -ETIMEDOUT;
+
+ if (!i2c->addr_hit)
+ return -ENXIO;
+
+ regmap_write(i2c->map, ANDES_I2C_INTEN_REG, 0);
+ reinit_completion(&i2c->completion);
+ } else {
+ unsigned int val;
+ int ret;
+
+ mask = ANDES_I2C_STATUS_CMPL;
+ mask |= (msg->flags & I2C_M_RD) ? ANDES_I2C_STATUS_FIFO_FULL
+ : ANDES_I2C_STATUS_FIFO_EMPTY;
+ while (!i2c->xfer_done) {
+ ret = regmap_read_poll_timeout(i2c->map,
+ ANDES_I2C_STATUS_REG,
+ val, val & mask, 2000,
+ ANDES_I2C_TIMEOUT_US);
+ if (ret)
+ return ret;
+
+ andes_i2c_xfer_common(i2c, val);
+ }
+
+ if (!i2c->addr_hit)
+ return -ENXIO;
+ }
+
+ /* Check if all data is successfully transmitted */
+ regmap_read(i2c->map, ANDES_I2C_CTRL_REG, &i2c_ctrl);
+ if (FIELD_GET(ANDES_I2C_CTRL_DATA_CNT, i2c_ctrl))
+ return -EIO;
+
+ return 0;
+}
+
+static int andes_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
+ int num)
+{
+ int i;
+ struct i2c_msg *m;
+ struct andes_i2c *i2c = i2c_get_adapdata(adap);
+ int ret;
+
+ for (i = 0; i < num; i++) {
+ m = &msg[i];
+ i2c->addr_hit = false;
+ i2c->buf = m->buf;
+ i2c->buf_len = m->len;
+ i2c->xfer_done = false;
+ ret = andes_i2c_xfer_wait(i2c, m);
+ if (ret < 0)
+ return ret;
+ }
+
+ return num;
+}
+
+static u32 andes_i2c_func(struct i2c_adapter *adap)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm andes_i2c_algo = {
+ .xfer = andes_i2c_xfer,
+ .functionality = andes_i2c_func,
+};
+
+static const struct i2c_adapter_quirks andes_i2c_quirks = {
+ .flags = I2C_AQ_NO_ZERO_LEN,
+ .max_write_len = ANDES_I2C_MAX_DATA_LEN,
+ .max_read_len = ANDES_I2C_MAX_DATA_LEN,
+};
+
+static int andes_i2c_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct andes_i2c *i2c;
+ void __iomem *reg_base;
+ u32 i2c_id;
+ int ret;
+ struct i2c_adapter *adap;
+
+ i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
+ if (!i2c)
+ return -ENOMEM;
+
+ reg_base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(reg_base))
+ return dev_err_probe(dev, PTR_ERR(reg_base),
+ "failed to map I/O space\n");
+
+ i2c->map = devm_regmap_init_mmio(dev, reg_base,
+ &andes_i2c_regmap_config);
+ if (IS_ERR(i2c->map))
+ return dev_err_probe(dev, PTR_ERR(i2c->map),
+ "failed to initialize regmap\n");
+
+ regmap_read(i2c->map, ANDES_I2C_ID_REG, &i2c_id);
+ if (FIELD_GET(ANDES_I2C_ID_MASK, i2c_id) != ANDES_I2C_ID)
+ return dev_err_probe(dev, -ENODEV, "unmatched hardware ID 0x%x\n",
+ i2c_id);
+
+ i2c->irq = platform_get_irq(pdev, 0);
+ if (i2c->irq >= 0) {
+ ret = devm_request_irq(dev, i2c->irq, andes_i2c_irq_handler, 0,
+ dev_name(dev), i2c);
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "unable to request IRQ %d\n",
+ i2c->irq);
+ } else {
+ dev_warn(dev, "no IRQ resource, falling back to poll mode\n");
+ }
+
+ spin_lock_init(&i2c->lock);
+ init_completion(&i2c->completion);
+ adap = &i2c->adap;
+ strscpy(adap->name, pdev->name, sizeof(adap->name));
+ adap->algo = &andes_i2c_algo;
+ adap->class = I2C_CLASS_HWMON;
+ adap->dev.parent = dev;
+ adap->dev.of_node = dev->of_node;
+ adap->owner = THIS_MODULE;
+ adap->quirks = &andes_i2c_quirks;
+ adap->retries = 1;
+ adap->timeout = ANDES_I2C_TIMEOUT;
+ i2c_set_adapdata(adap, i2c);
+ platform_set_drvdata(pdev, i2c);
+ ret = devm_i2c_add_adapter(dev, adap);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to add adapter\n");
+
+ regmap_read(i2c->map, ANDES_I2C_CFG_REG, &i2c->fifo_size);
+ i2c->fifo_size = 2 << FIELD_GET(ANDES_I2C_CFG_FIFOSIZE, i2c->fifo_size);
+
+ regmap_set_bits(i2c->map, ANDES_I2C_SETUP_REG,
+ ANDES_I2C_SETUP_IICEN | ANDES_I2C_SETUP_REQ);
+ return 0;
+}
+
+static const struct of_device_id andes_i2c_of_match[] = {
+ { .compatible = "andestech,ae350-i2c" },
+ { /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, andes_i2c_of_match);
+
+static struct platform_driver andes_i2c_platform_driver = {
+ .driver = {
+ .name = "andes_i2c",
+ .of_match_table = andes_i2c_of_match,
+ },
+ .probe = andes_i2c_probe,
+};
+
+module_platform_driver(andes_i2c_platform_driver);
+
+MODULE_AUTHOR("Ben Zong-You Xie <ben717@andestech.com>");
+MODULE_DESCRIPTION("Andes I2C controller driver");
+MODULE_LICENSE("GPL");
--
2.34.1
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