[PATCH v2] i2c: add support for the MT7621 I2C controller
Justin Swartz
justin.swartz at risingedge.co.za
Wed Oct 8 12:22:56 CEST 2025
This commit introduces a port of the Linux kernel's driver for the
Mediatek's MT7621 I2C controller.
The port was undertaken as the existing driver intended for Mediatek
I2C controllers (mtk_i2c.c) is not compatible with the MT7621.
To use the driver:
1. Ensure that the mode of the i2c pin group is
configured for "i2c" rather than "gpio".
2. Delete the existing (bitbanged) i2c node from
arch/mips/dts/mt7621.dtsi, or specify:
/delete-node/ &i2c;
3. Declare:
i2c: i2c at 1e000900 {
compatible = "mediatek,mt7621-i2c";
reg = <0x1e000900 0x100>;
clocks = <&clk50m>;
clock-names = "sys_clock";
resets = <&rstctrl RST_I2C>;
reset-names = "i2c_reset";
pinctrl-names = "default";
pinctrl-0 = <&i2c_pins>;
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
};
Signed-off-by: Justin Swartz <justin.swartz at risingedge.co.za>
---
Notes:
[PATCH v2]
- Add "REG_" prefix to I2C (Serial Master 0) register definitions.
- Remove unused "PINT" (Peripheral Interrupt) register definitions.
- Adjust function definition style.
- Refactor mt7621_i2c_check_ack() to accept the number of bytes
expected to have been acknowledged, instead of accepting a
literal value (which represents the acknowledgement status of
(up to) 8 bytes, encoded as 8 independent bit values) expected
in the SM0_ACK field (bits 23:16) of the SM0CTL1 register.
drivers/i2c/Kconfig | 7 +
drivers/i2c/Makefile | 1 +
drivers/i2c/mt7621_i2c.c | 372 +++++++++++++++++++++++++++++++++++++++
3 files changed, 380 insertions(+)
create mode 100644 drivers/i2c/mt7621_i2c.c
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 108b24b3dd2..bdd3c60118c 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -308,6 +308,13 @@ config SYS_I2C_MTK
If you want to use MediaTek I2C interface, say Y here.
If unsure, say N.
+config SYS_I2C_MT7621
+ bool "Mediatek MT7621 I2C driver"
+ help
+ This selects the Mediatek MT7621 I2C driver.
+ If you want to use the MediaTek MT7621 I2C controller, say Y here.
+ If unsure, say N.
+
config SYS_I2C_MICROCHIP
bool "Microchip I2C driver"
help
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 42326db85f6..5fe30d0df4f 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_SYS_I2C_MV) += mv_i2c.o
obj-$(CONFIG_SYS_I2C_MVTWSI) += mvtwsi.o
obj-$(CONFIG_SYS_I2C_MXC) += mxc_i2c.o
obj-$(CONFIG_SYS_I2C_MTK) += mtk_i2c.o
+obj-$(CONFIG_SYS_I2C_MT7621) += mt7621_i2c.o
obj-$(CONFIG_SYS_I2C_NEXELL) += nx_i2c.o
obj-$(CONFIG_SYS_I2C_NPCM) += npcm_i2c.o
obj-$(CONFIG_SYS_I2C_OCORES) += ocores_i2c.o
diff --git a/drivers/i2c/mt7621_i2c.c b/drivers/i2c/mt7621_i2c.c
new file mode 100644
index 00000000000..292e582fd8d
--- /dev/null
+++ b/drivers/i2c/mt7621_i2c.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * U-Boot driver for the MediaTek MT7621 I2C controller.
+ *
+ * Derived from the Linux kernel driver:
+ * drivers/i2c/busses/i2c-mt7621.c
+ *
+ * Copyright (C) 2013 Steven Liu <steven_liu at mediatek.com>
+ * Copyright (C) 2014 Sittisak <sittisaks at hotmail.com>
+ * Copyright (C) 2016 Michael Lee <igvtee at gmail.com>
+ * Copyright (C) 2018 Jan Breuer <jan.breuer at jaybee.cz>
+ * Copyright (C) 2025 Justin Swartz <justin.swartz at risingedge.co.za>
+ */
+
+#include <asm/io.h>
+#include <dm/device.h>
+#include <dm/device_compat.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/printk.h>
+#include <dm.h>
+#include <clk.h>
+#include <common.h>
+#include <i2c.h>
+#include <log.h>
+#include <reset.h>
+
+#define REG_SM0CFG2 0x28
+#define REG_SM0CTL0 0x40
+#define REG_SM0CTL1 0x44
+#define REG_SM0D0 0x50
+#define REG_SM0D1 0x54
+
+#define SM0CFG2_MODE_MANUAL 0
+
+#define SM0CTL0_ODRAIN BIT(31)
+#define SM0CTL0_CLK_DIV_MASK (0x7ff << 16)
+#define SM0CTL0_CLK_DIV_MAX 0x7ff
+#define SM0CTL0_EN BIT(1)
+#define SM0CTL0_SCL_STRETCH BIT(0)
+
+#define SM0CTL1_TRI BIT(0)
+#define SM0CTL1_TRI_IDLE 0
+#define SM0CTL1_START (1 << 4)
+#define SM0CTL1_WRITE (2 << 4)
+#define SM0CTL1_STOP (3 << 4)
+#define SM0CTL1_READ_LAST (4 << 4)
+#define SM0CTL1_READ (5 << 4)
+#define SM0CTL1_PGLEN(x) ((((x) - 1) << 8) & SM0CTL1_PGLEN_MASK)
+#define SM0CTL1_PGLEN_MASK (0x7 << 8)
+#define SM0CTL1_ACK_MASK (0xff << 16)
+
+#define TIMEOUT_1SEC 1000
+#define I2C_MAX_STD_MODE_FREQ 100000
+
+struct mt7621_i2c_priv
+{
+ void __iomem *base;
+ uint speed;
+ u32 clk_div;
+ struct clk clk;
+ struct reset_ctl reset_ctl;
+};
+
+static int mt7621_i2c_wait_idle(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ ulong start_time = get_timer(0);
+ u32 value;
+
+ while (get_timer(start_time) < TIMEOUT_1SEC) {
+ value = readl(priv->base + REG_SM0CTL1);
+ if ((value & SM0CTL1_TRI) == SM0CTL1_TRI_IDLE)
+ return 0;
+
+ udelay(10);
+ }
+
+ return -ETIMEDOUT;
+}
+
+static int mt7621_i2c_reset(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ u32 value;
+
+ reset_assert(&priv->reset_ctl);
+ udelay(100);
+ reset_deassert(&priv->reset_ctl);
+
+ value = readl(priv->base + REG_SM0CTL0);
+ value &= ~SM0CTL0_CLK_DIV_MASK;
+ value |= (priv->clk_div << 16) & SM0CTL0_CLK_DIV_MASK;
+ value |= SM0CTL0_EN | SM0CTL0_SCL_STRETCH;
+ writel(value, priv->base + REG_SM0CTL0);
+
+ writel(SM0CFG2_MODE_MANUAL, priv->base + REG_SM0CFG2);
+ return 0;
+}
+
+static int mt7621_i2c_master_start(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ writel(SM0CTL1_START | SM0CTL1_TRI, priv->base + REG_SM0CTL1);
+ return mt7621_i2c_wait_idle(dev);
+}
+
+static int mt7621_i2c_master_stop(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ writel(SM0CTL1_STOP | SM0CTL1_TRI, priv->base + REG_SM0CTL1);
+ return mt7621_i2c_wait_idle(dev);
+}
+
+static int mt7621_i2c_master_cmd(struct udevice *dev, u32 cmd, int len)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ writel(cmd | SM0CTL1_TRI | SM0CTL1_PGLEN(len),
+ priv->base + REG_SM0CTL1);
+ return mt7621_i2c_wait_idle(dev);
+}
+
+static int mt7621_i2c_7bit_address(struct udevice *dev, struct i2c_msg *msg)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+
+ u32 addr = (msg->addr << 1) | ((msg->flags & I2C_M_RD) ? 1 : 0);
+ writel(addr, priv->base + REG_SM0D0);
+
+ return mt7621_i2c_master_cmd(dev, SM0CTL1_WRITE, 1);
+}
+
+static int mt7621_i2c_10bit_address(struct udevice *dev, struct i2c_msg *msg)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+
+ u16 addr = 0xf0 | ((msg->addr >> 7) & 0x06) | (msg->addr & 0xff) << 8;
+ if (msg->flags & I2C_M_RD)
+ addr |= 1;
+ writel(addr, priv->base + REG_SM0D0);
+
+ return mt7621_i2c_master_cmd(dev, SM0CTL1_WRITE, 2);
+}
+
+static int mt7621_i2c_address(struct udevice *dev, struct i2c_msg *msg)
+{
+ int ret;
+
+ if (msg->flags & I2C_M_TEN) {
+ ret = mt7621_i2c_10bit_address(dev, msg);
+ if (ret)
+ return ret;
+ }
+
+ else {
+ ret = mt7621_i2c_7bit_address(dev, msg);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int mt7621_i2c_check_ack(struct udevice *dev, struct i2c_msg *msg,
+ u32 length)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+
+ if (msg->flags & I2C_M_IGNORE_NAK)
+ return 0;
+
+ u32 status = *(volatile u32 *)(priv->base + REG_SM0CTL1);
+ u32 expected = GENMASK(length - 1, 0);
+ u32 mask = (expected << 16) & SM0CTL1_ACK_MASK;
+
+ if ((status & mask) != mask)
+ return -ENXIO;
+
+ return 0;
+}
+
+static int mt7621_i2c_master_read(struct udevice *dev, struct i2c_msg *msg)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ int offset, length, last, ret;
+ u32 cmd;
+ u32 data[2];
+
+ for (offset = 0; offset < msg->len; offset += 8) {
+ if (msg->len - offset >= 8)
+ length = 8;
+ else
+ length = msg->len - offset;
+
+ last = msg->len - offset <= 8;
+ cmd = last ? SM0CTL1_READ_LAST : SM0CTL1_READ;
+ ret = mt7621_i2c_master_cmd(dev, cmd, length);
+ if (ret)
+ return ret;
+
+ data[0] = readl(priv->base + REG_SM0D0);
+ data[1] = readl(priv->base + REG_SM0D1);
+ memcpy(&msg->buf[offset], data, length);
+ }
+
+ return 0;
+}
+
+static int mt7621_i2c_master_write(struct udevice *dev, struct i2c_msg *msg)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ int offset, length, ret;
+ u32 data[2];
+
+ for (offset = 0; offset < msg->len; offset += 8) {
+ if (msg->len - offset >= 8)
+ length = 8;
+ else
+ length = msg->len - offset;
+
+ memcpy(data, &msg->buf[offset], length);
+ writel(data[0], priv->base + REG_SM0D0);
+ writel(data[1], priv->base + REG_SM0D1);
+
+ ret = mt7621_i2c_master_cmd(dev, SM0CTL1_WRITE, length);
+ if (ret)
+ return ret;
+
+ ret = mt7621_i2c_check_ack(dev, msg, length);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int mt7621_i2c_xfer(struct udevice *dev, struct i2c_msg *msgs, int count)
+{
+ struct i2c_msg *msg;
+ int index, ret;
+
+ for (index = 0; index < count; index++) {
+ msg = &msgs[index];
+
+ ret = mt7621_i2c_wait_idle(dev);
+ if (ret)
+ goto reset;
+
+ ret = mt7621_i2c_master_start(dev);
+ if (ret)
+ goto reset;
+
+ ret = mt7621_i2c_address(dev, msg);
+ if (ret)
+ goto reset;
+
+ ret = mt7621_i2c_check_ack(dev, msg, 1);
+ if (ret)
+ goto stop;
+
+ if (msg->flags & I2C_M_RD) {
+ ret = mt7621_i2c_master_read(dev, msg);
+ if (ret)
+ goto reset;
+ }
+ else {
+ ret = mt7621_i2c_master_write(dev, msg);
+ if (ret)
+ goto reset;
+ }
+ }
+
+ ret = mt7621_i2c_wait_idle(dev);
+ if (ret)
+ goto reset;
+
+ ret = mt7621_i2c_master_stop(dev);
+ if (ret)
+ goto reset;
+
+ return 0;
+
+stop:
+ ret = mt7621_i2c_master_stop(dev);
+ if (ret)
+ goto reset;
+ return -ENXIO;
+
+reset:
+ mt7621_i2c_reset(dev);
+ return ret;
+}
+
+static int mt7621_i2c_set_speed(struct udevice *dev, uint speed)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ ulong clk_rate = clk_get_rate(&priv->clk);
+
+ priv->speed = speed;
+ priv->clk_div = clk_rate / priv->speed - 1;
+
+ if (priv->clk_div < 99)
+ priv->clk_div = 99;
+
+ if (priv->clk_div > SM0CTL0_CLK_DIV_MAX)
+ priv->clk_div = SM0CTL0_CLK_DIV_MAX;
+
+ return 0;
+}
+
+static const struct dm_i2c_ops mt7621_i2c_ops = {
+ .xfer = mt7621_i2c_xfer,
+ .set_bus_speed = mt7621_i2c_set_speed,
+ .deblock = mt7621_i2c_reset,
+};
+
+static int mt7621_i2c_of_to_plat(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ priv->base = dev_remap_addr(dev);
+ return 0;
+}
+
+int mt7621_i2c_probe(struct udevice *dev)
+{
+ struct mt7621_i2c_priv *priv = dev_get_priv(dev);
+ int ret;
+
+ priv->base = dev_remap_addr(dev);
+ if (!priv->base) {
+ dev_err(dev, "failed to get base address\n");
+ return -EINVAL;
+ }
+
+ ret = clk_get_by_name(dev, "sys_clock", &priv->clk);
+ if (ret) {
+ dev_err(dev, "failed to get clock source\n");
+ return ret;
+ }
+
+ ret = reset_get_by_name(dev, "i2c_reset", &priv->reset_ctl);
+ if (ret) {
+ dev_err(dev, "failed to get reset control\n");
+ return ret;
+ }
+
+ ret = clk_enable(&priv->clk);
+ if (ret) {
+ dev_err(dev, "failed to enable clock\n");
+ return ret;
+ }
+
+ mt7621_i2c_set_speed(dev, I2C_MAX_STD_MODE_FREQ);
+ mt7621_i2c_reset(dev);
+
+ return 0;
+}
+
+static const struct udevice_id mt7621_i2c_ids[] = {
+ { .compatible = "mediatek,mt7621-i2c" },
+ { }
+};
+
+U_BOOT_DRIVER(mt7621_i2c) = {
+ .name = "mt7621_i2c",
+ .id = UCLASS_I2C,
+ .of_match = mt7621_i2c_ids,
+ .of_to_plat = mt7621_i2c_of_to_plat,
+ .probe = mt7621_i2c_probe,
+ .priv_auto = sizeof(struct mt7621_i2c_priv),
+ .ops = &mt7621_i2c_ops,
+};
--
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