[PATCH v8 0/2] riscv: spacemit: add i2c support to K1 SoC

[PATCH v8 0/2] riscv: spacemit: add i2c support to K1 SoC

[Troy Mitchell]

Hi all,

This patch implements I2C driver for the SpacemiT K1 SoC,
providing basic support for I2C read/write communication which
compatible with standard I2C bus specifications.

In this version, the driver defaults to use fast-speed-mode and
interrupts for transmission, and does not support DMA, high-speed mode, or FIFO.

The docs of I2C can be found here, in chapter 16.1 I2C [1]

Link: https://developer.spacemit.com/documentation?token=Rn9Kw3iFHirAMgkIpTAcV2Arnkf#part5 [1]
---
Changes in v8:
- Patch #2:
        - Fix code style
        - Fix comment style
- Link to v7: https://lore.kernel.org/r/20250316-k1-i2c-master-v7-0-f2d5c43e2f40@gmail.com

Changes in v7:
- Patch #2:
        - Adjust structure member types  
        - Default to 400,000 Hz if `clock-frequency` is unavailable  
        - Fix code style
        - Fix comments  
        - Kconfig: Rename "Spacemit" to "SpacemiT"  
        - Use local variables in `spacemit_xfer_msgs`
        - Rename `spacemit_i2c_wait_bus_busy` to `spacemit_i2c_wait_bus_idle`
        - Reduce transmission timeout in `spacemit_i2c_calc_timeout`  
Link to v6:
https://lore.kernel.org/r/20250307-k1-i2c-master-v6-0-34f17d2dae1c@gmail.com

Change in v6:
- Patch #1:
        - Give a brief clock description and a clear clock name
        - Changed the clock numbers in the example to match those
          in the mainline clock driver
- Patch #2:
        - Fix incorrect comments in macro definitions
        - Fix code style
        - Merge `spacemit_i2c_xfer_core` into `spacemit_i2c_xfer`
        - Remove `reset` and `enable_irq` before each transfer
          and place `reset` in the probe function.
        - SPACEMIT_I2C_GET_ERR -> SPACEMIT_I2C_SR_ERR
        - spacemit_i2c_recover_bus_busy -> spacemit_i2c_wait_bus_busy
        - Support standard mode
Link to v5:
https://lore.kernel.org/all/20250303-k1-i2c-master-v5-0-21dfc7adfe37@gmail.com/

Change in v5:
- Patch #1:
        - Add `clock-names` property
        - Modify the clock property into two
- Patch #2:
        - Enable the APB clock
        - Fix comment and code styles
        - Fix typo and drop unnecessary description in Kconfig
        - Prefix all macro definitions with SPACEMIT_
        - Rename `spacemit_i2c_bus_reset` to `spacemit_i2c_conditionally_reset_bus`
        - Remove all `unlikely` and `likely`
        - Remove unused register and bit macros
        - Remove the "err" field, as it only contains a subset of the status field
        - Retrieve `clock-frequency` from the device tree instead of using a macro
        - Use a local variable to track the current message
        - Use `i2c->read` to represent read and write statuses instead of `i2c->dir`
Link to v4:
https://lore.kernel.org/all/20241125-k1-i2c-master-v4-0-0f3d5886336b@gmail.com/

Change in v4:
- Patch #1:
	- Change the default value of clock-frequency from 100000 to
	  400000. This is to correspond to the driver's default value.
	- Drop the minimum of clock-frequency
	- Modify the description of clock-frequency
- Patch #2:
	- Drop the `inline` qualifier from the `spacemit_i2c_xfer_core` function
	- Drop the initialization of `ret` to 0 in `spacemit_i2c_xfer_core` function
	- Drop useless wrap
Link to v3:
https://lore.kernel.org/all/20241112-k1-i2c-master-v3-0-5005b70dc208@gmail.com/

Change in v3:
- Patch #1:
	- Change the maxItems of reg from 2 to 1 in properties
	- Modify reg in dts example
	- Changed the enum selection for clock-frequency to a range,
	  setting a minimum value of 1 and a maximum value of 3,300,000.
- Patch #2:
	- Drop unused judgement in `spacemit_i2c_xfer_msg`
	- Fix the dangling else warning in `spacemit_i2c_is_last_msg`
	- Fix the error check for `i2c->base`
	- Modify Kconfig dependencies
Link to v2:
https://lore.kernel.org/all/20241028053220.346283-1-TroyMitchell988@gmail.com/

Change in v2:
- Patch #1:
	- Change the maxItems of reg from 1 to 2 in properties
	- Change 'i2c' to 'I2C' in the commit message.
	- Drop fifo-disable property
	- Drop alias in dts example
	- Move `unevaluatedProperties` after `required:` block
- Patch #2:
	- Alphabetize Makefile and Kconfig
	- Change `.remove_new` to `.remove` in `struct platform_driver`
	- Change `dev_alert` to `dev_warn_ratelimited` in `spacemit_i2c_bus_reset`
	- Change `spacemit_i2c_read/write_reg` to `read/writel`
	- Change `spacemit_i2c_dt_match` to `spacemit_i2c_of_match`
	- Clean up code flow
	- Fix unnecessary line wraps
	- Move `spacemit_i2c_handle_err` to a suitable location
	- Modify Kconfig dependencies
	- Use `PTR_ERR(i2c->base)` directly as the `dev_err_probe` parameter instead of
	  the intermediate variable
Link to v1:
https://lore.kernel.org/all/20241015075134.1449458-1-TroyMitchell988@gmail.com/

---
Troy Mitchell (2):
      dt-bindings: i2c: spacemit: add support for K1 SoC
      i2c: spacemit: add support for SpacemiT K1 SoC

 .../devicetree/bindings/i2c/spacemit,k1-i2c.yaml   |  61 +++
 drivers/i2c/busses/Kconfig                         |  17 +
 drivers/i2c/busses/Makefile                        |   1 +
 drivers/i2c/busses/i2c-k1.c                        | 602 +++++++++++++++++++++
 4 files changed, 681 insertions(+)
---
base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354
change-id: 20241031-k1-i2c-master-fe7f7b0dce93
prerequisite-change-id: 20240626-k1-01-basic-dt-1aa31eeebcd2:v5
prerequisite-patch-id: 47dcf6861f7d434d25855b379e6d7ef4ce369c9c
prerequisite-patch-id: 77787fe82911923aff15ccf565e8fa451538c3a6
prerequisite-patch-id: b0bdb1742d96c5738f05262c3b0059102761390b
prerequisite-patch-id: 3927d39d8d77e35d5bfe53d9950da574ff8f2054
prerequisite-patch-id: a98039136a4796252a6029e474f03906f2541643
prerequisite-patch-id: c95f6dc0547a2a63a76e3cba0cf5c623b212b4e6
prerequisite-patch-id: 66e750e438ee959ddc2a6f0650814a2d8c989139
prerequisite-patch-id: 29a0fd8c36c1a4340f0d0b68a4c34d2b8abfb1ab
prerequisite-patch-id: 0bdfff661c33c380d1cf00a6c68688e05f88c0b3
prerequisite-patch-id: 99f15718e0bfbb7ed1a96dfa19f35841b004dae9

Best regards,
-- 
Troy Mitchell <troymitchell988@gmail.com>

[PATCH v8 1/2] dt-bindings: i2c: spacemit: add support for K1 SoC

[Troy Mitchell]

The I2C of K1 supports fast-speed-mode and high-speed-mode,
and supports FIFO transmission.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/all/20250128-k1-maintainer-1-v1-1-e5dec4f379eb@gentoo.org [1]
Signed-off-by: Troy Mitchell <troymitchell988@gmail.com>
---
 .../devicetree/bindings/i2c/spacemit,k1-i2c.yaml   | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/spacemit,k1-i2c.yaml b/Documentation/devicetree/bindings/i2c/spacemit,k1-i2c.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..3d6aefb0d0f185ba64e414ac7f5b96cd18659fd3
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/spacemit,k1-i2c.yaml
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/i2c/spacemit,k1-i2c.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: I2C controller embedded in SpacemiT's K1 SoC
+
+maintainers:
+  - Troy Mitchell <troymitchell988@gmail.com>
+
+properties:
+  compatible:
+    const: spacemit,k1-i2c
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: I2C Functional Clock
+      - description: APB Bus Clock
+
+  clock-names:
+    items:
+      - const: func
+      - const: bus
+
+  clock-frequency:
+    description: |
+      K1 support three different modes which running different frequencies
+      standard speed mode: up to 100000 (100Hz)
+      fast speed mode    : up to 400000 (400Hz)
+      high speed mode    : up to 3300000 (3.3Mhz)
+    default: 400000
+    maximum: 3300000
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c@d4010800 {
+        compatible = "spacemit,k1-i2c";
+        reg = <0xd4010800 0x38>;
+        interrupt-parent = <&plic>;
+        interrupts = <36>;
+        clocks =<&ccu 32>, <&ccu 84>;
+        clock-names = "func", "bus";
+        clock-frequency = <100000>;
+    };
+
+...

-- 
2.34.1

[PATCH v8 2/2] i2c: spacemit: add support for SpacemiT K1 SoC

[Troy Mitchell]

This patch introduces basic I2C support for the SpacemiT K1 SoC,
utilizing interrupts for transfers.

The driver has been tested using i2c-tools on a Bananapi-F3 board,
and basic I2C read/write operations have been confirmed to work.

Reviewed-by: Alex Elder <elder@riscstar.com>
Link: https://lore.kernel.org/all/20250128-k1-maintainer-1-v1-1-e5dec4f379eb@gentoo.org [1]
Signed-off-by: Troy Mitchell <troymitchell988@gmail.com>
---
 drivers/i2c/busses/Kconfig  |  17 ++
 drivers/i2c/busses/Makefile |   1 +
 drivers/i2c/busses/i2c-k1.c | 602 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 620 insertions(+)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index fc438f4457713d5559d163840a7b11e8cdbb8f58..41dd05644c43a8630a6d53f70ec7fbf899d297b5 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -783,6 +783,23 @@ config I2C_JZ4780
 
 	 If you don't know what to do here, say N.
 
+config I2C_K1
+	tristate "SpacemiT K1 I2C adapter"
+	depends on ARCH_SPACEMIT || COMPILE_TEST
+	depends on OF
+	help
+	  This option enables support for the I2C interface on the SpacemiT K1
+	  platform.
+
+	  If you enable this configuration, the kernel will include support for
+	  the I2C adapter specific to the SpacemiT K1 platform. This driver can
+	  be used to manage I2C bus transactions, which are necessary for
+	  interfacing with I2C peripherals such as sensors, EEPROMs, and other
+	  devices.
+
+	  This driver can also be built as a module.  If so, the
+	  module will be called `i2c-k1`.
+
 config I2C_KEBA
 	tristate "KEBA I2C controller support"
 	depends on HAS_IOMEM
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 1c2a4510abe44a689dfe67d2d64cf0cf3434f510..c1252e2b779e2e47492d66179b442f2202ec0416 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -74,6 +74,7 @@ obj-$(CONFIG_I2C_IMX)		+= i2c-imx.o
 obj-$(CONFIG_I2C_IMX_LPI2C)	+= i2c-imx-lpi2c.o
 obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
 obj-$(CONFIG_I2C_JZ4780)	+= i2c-jz4780.o
+obj-$(CONFIG_I2C_K1)		+= i2c-k1.o
 obj-$(CONFIG_I2C_KEBA)		+= i2c-keba.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
 obj-$(CONFIG_I2C_LPC2K)		+= i2c-lpc2k.o
diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
new file mode 100644
index 0000000000000000000000000000000000000000..0d8763b852db9829c6d5adc0ee99c1f3d8176290
--- /dev/null
+++ b/drivers/i2c/busses/i2c-k1.c
@@ -0,0 +1,602 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024-2025 Troy Mitchell <troymitchell988@gmail.com>
+ */
+
+ #include <linux/clk.h>
+ #include <linux/i2c.h>
+ #include <linux/iopoll.h>
+ #include <linux/module.h>
+ #include <linux/of_address.h>
+ #include <linux/platform_device.h>
+
+/* spacemit i2c registers */
+#define SPACEMIT_ICR		 0x0		/* Control register */
+#define SPACEMIT_ISR		 0x4		/* Status register */
+#define SPACEMIT_IDBR		 0xc		/* Data buffer register */
+#define SPACEMIT_IBMR		 0x1c		/* Bus monitor register */
+
+/* SPACEMIT_ICR register fields */
+#define SPACEMIT_CR_START        BIT(0)		/* start bit */
+#define SPACEMIT_CR_STOP         BIT(1)		/* stop bit */
+#define SPACEMIT_CR_ACKNAK       BIT(2)		/* send ACK(0) or NAK(1) */
+#define SPACEMIT_CR_TB           BIT(3)		/* transfer byte bit */
+/* Bits 4-7 are reserved */
+#define SPACEMIT_CR_MODE_FAST    BIT(8)		/* bus mode (master operation) */
+/* Bit 9 is reserved */
+#define SPACEMIT_CR_UR           BIT(10)	/* unit reset */
+/* Bits 11-12 are reserved */
+#define SPACEMIT_CR_SCLE         BIT(13)	/* master clock enable */
+#define SPACEMIT_CR_IUE          BIT(14)	/* unit enable */
+/* Bits 15-17 are reserved */
+#define SPACEMIT_CR_ALDIE        BIT(18)	/* enable arbitration interrupt */
+#define SPACEMIT_CR_DTEIE        BIT(19)	/* enable TX interrupts */
+#define SPACEMIT_CR_DRFIE        BIT(20)	/* enable RX interrupts */
+#define SPACEMIT_CR_GCD          BIT(21)	/* general call disable */
+#define SPACEMIT_CR_BEIE         BIT(22)	/* enable bus error ints */
+/* Bits 23-24 are reserved */
+#define SPACEMIT_CR_MSDIE        BIT(25)	/* master STOP detected int enable */
+#define SPACEMIT_CR_MSDE         BIT(26)	/* master STOP detected enable */
+#define SPACEMIT_CR_TXDONEIE     BIT(27)	/* transaction done int enable */
+#define SPACEMIT_CR_TXEIE        BIT(28)	/* transmit FIFO empty int enable */
+#define SPACEMIT_CR_RXHFIE       BIT(29)	/* receive FIFO half-full int enable */
+#define SPACEMIT_CR_RXFIE        BIT(30)	/* receive FIFO full int enable */
+#define SPACEMIT_CR_RXOVIE       BIT(31)	/* receive FIFO overrun int enable */
+
+#define SPACEMIT_I2C_INT_CTRL_MASK	(SPACEMIT_CR_ALDIE | SPACEMIT_CR_DTEIE | \
+					 SPACEMIT_CR_DRFIE | SPACEMIT_CR_BEIE | \
+					 SPACEMIT_CR_TXDONEIE | SPACEMIT_CR_TXEIE | \
+					 SPACEMIT_CR_RXHFIE | SPACEMIT_CR_RXFIE | \
+					 SPACEMIT_CR_RXOVIE | SPACEMIT_CR_MSDIE)
+
+/* SPACEMIT_ISR register fields */
+/* Bits 0-13 are reserved */
+#define SPACEMIT_SR_ACKNAK       BIT(14)	/* ACK/NACK status */
+#define SPACEMIT_SR_UB           BIT(15)	/* unit busy */
+#define SPACEMIT_SR_IBB          BIT(16)	/* i2c bus busy */
+#define SPACEMIT_SR_EBB          BIT(17)	/* early bus busy */
+#define SPACEMIT_SR_ALD          BIT(18)	/* arbitration loss detected */
+#define SPACEMIT_SR_ITE          BIT(19)	/* TX buffer empty */
+#define SPACEMIT_SR_IRF          BIT(20)	/* RX buffer full */
+#define SPACEMIT_SR_GCAD         BIT(21)	/* general call address detected */
+#define SPACEMIT_SR_BED          BIT(22)	/* bus error no ACK/NAK */
+#define SPACEMIT_SR_SAD          BIT(23)	/* slave address detected */
+#define SPACEMIT_SR_SSD          BIT(24)	/* slave stop detected */
+/* Bit 25 is reserved */
+#define SPACEMIT_SR_MSD          BIT(26)	/* master stop detected */
+#define SPACEMIT_SR_TXDONE       BIT(27)	/* transaction done */
+#define SPACEMIT_SR_TXE          BIT(28)	/* TX FIFO empty */
+#define SPACEMIT_SR_RXHF         BIT(29)	/* RX FIFO half-full */
+#define SPACEMIT_SR_RXF          BIT(30)	/* RX FIFO full */
+#define SPACEMIT_SR_RXOV         BIT(31)	/* RX FIFO overrun */
+
+#define SPACEMIT_I2C_INT_STATUS_MASK	(SPACEMIT_SR_RXOV | SPACEMIT_SR_RXF | SPACEMIT_SR_RXHF | \
+					SPACEMIT_SR_TXE | SPACEMIT_SR_TXDONE | SPACEMIT_SR_MSD | \
+					SPACEMIT_SR_SSD | SPACEMIT_SR_SAD | SPACEMIT_SR_BED | \
+					SPACEMIT_SR_GCAD | SPACEMIT_SR_IRF | SPACEMIT_SR_ITE | \
+					SPACEMIT_SR_ALD)
+
+/* SPACEMIT_IBMR register fields */
+#define SPACEMIT_BMR_SDA         BIT(0)		/* SDA line level */
+#define SPACEMIT_BMR_SCL         BIT(1)		/* SCL line level */
+
+/* i2c bus recover timeout: us */
+#define SPACEMIT_I2C_BUS_BUSY_TIMEOUT		100000
+
+#define SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ	100000	/* Hz */
+#define SPACEMIT_I2C_MAX_FAST_MODE_FREQ		400000	/* Hz */
+
+#define SPACEMIT_SR_ERR	(SPACEMIT_SR_BED | SPACEMIT_SR_RXOV | SPACEMIT_SR_ALD)
+
+enum spacemit_i2c_state {
+	SPACEMIT_STATE_IDLE,
+	SPACEMIT_STATE_START,
+	SPACEMIT_STATE_READ,
+	SPACEMIT_STATE_WRITE,
+};
+
+/* i2c-spacemit driver's main struct */
+struct spacemit_i2c_dev {
+	struct device *dev;
+	struct i2c_adapter adapt;
+
+	/* hardware resources */
+	void __iomem *base;
+	int irq;
+	u32 clock_freq;
+
+	struct i2c_msg *msgs;
+	u32 msg_num;
+
+	/* index of the current message being processed */
+	u32 msg_idx;
+	u8 *msg_buf;
+	/* the number of unprocessed bytes remaining in the current message  */
+	u32 unprocessed;
+
+	enum spacemit_i2c_state state;
+	bool read;
+	struct completion complete;
+	u32 status;
+};
+
+static void spacemit_i2c_enable(struct spacemit_i2c_dev *i2c)
+{
+	u32 val;
+
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val |= SPACEMIT_CR_IUE;
+	writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_disable(struct spacemit_i2c_dev *i2c)
+{
+	u32 val;
+
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val &= ~SPACEMIT_CR_IUE;
+	writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_reset(struct spacemit_i2c_dev *i2c)
+{
+	writel(SPACEMIT_CR_UR, i2c->base + SPACEMIT_ICR);
+	udelay(5);
+	writel(0, i2c->base + SPACEMIT_ICR);
+}
+
+static int spacemit_i2c_handle_err(struct spacemit_i2c_dev *i2c)
+{
+	dev_dbg(i2c->dev, "i2c error status: 0x%08x\n", i2c->status);
+
+	if (i2c->status & (SPACEMIT_SR_BED | SPACEMIT_SR_ALD)) {
+		spacemit_i2c_reset(i2c);
+		return -EAGAIN;
+	}
+
+	return i2c->status & SPACEMIT_SR_ACKNAK ? -ENXIO : -EIO;
+}
+
+static void spacemit_i2c_conditionally_reset_bus(struct spacemit_i2c_dev *i2c)
+{
+	u32 status;
+
+	/* if bus is locked, reset unit. 0: locked */
+	status = readl(i2c->base + SPACEMIT_IBMR);
+	if ((status & SPACEMIT_BMR_SDA) && (status & SPACEMIT_BMR_SCL))
+		return;
+
+	spacemit_i2c_reset(i2c);
+	usleep_range(10, 20);
+
+	/* check scl status again */
+	status = readl(i2c->base + SPACEMIT_IBMR);
+	if (!(status & SPACEMIT_BMR_SCL))
+		dev_warn_ratelimited(i2c->dev, "unit reset failed\n");
+}
+
+static int spacemit_i2c_wait_bus_idle(struct spacemit_i2c_dev *i2c)
+{
+	int ret;
+	u32 val;
+
+	val = readl(i2c->base + SPACEMIT_ISR);
+	if (!(val & (SPACEMIT_SR_UB | SPACEMIT_SR_IBB)))
+		return 0;
+
+	ret = readl_poll_timeout(i2c->base + SPACEMIT_ISR,
+				 val, !(val & (SPACEMIT_SR_UB | SPACEMIT_SR_IBB)),
+				 1500, SPACEMIT_I2C_BUS_BUSY_TIMEOUT);
+	if (ret)
+		spacemit_i2c_reset(i2c);
+
+	return ret;
+}
+
+static void spacemit_i2c_check_bus_release(struct spacemit_i2c_dev *i2c)
+{
+	/* in case bus is not released after transfer completes */
+	if (readl(i2c->base + SPACEMIT_ISR) & SPACEMIT_SR_EBB) {
+		spacemit_i2c_conditionally_reset_bus(i2c);
+		usleep_range(90, 150);
+	}
+}
+
+static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
+{
+	u32 val;
+
+	/*
+	 * Unmask interrupt bits for all xfer mode:
+	 * bus error, arbitration loss detected.
+	 * For transaction complete signal, we use master stop
+	 * interrupt, so we don't need to unmask SPACEMIT_CR_TXDONEIE.
+	 */
+	val = SPACEMIT_CR_BEIE | SPACEMIT_CR_ALDIE;
+
+	/*
+	 * Unmask interrupt bits for interrupt xfer mode:
+	 * When IDBR receives a byte, an interrupt is triggered.
+	 *
+	 * For the tx empty interrupt, it will be enabled in the
+	 * i2c_start function.
+	 * Otherwise, it will cause an erroneous empty interrupt before i2c_start.
+	 */
+	val |= SPACEMIT_CR_DRFIE;
+
+	if (i2c->clock_freq == SPACEMIT_I2C_MAX_FAST_MODE_FREQ)
+		val |= SPACEMIT_CR_MODE_FAST;
+
+	/* disable response to general call */
+	val |= SPACEMIT_CR_GCD;
+
+	/* enable SCL clock output */
+	val |= SPACEMIT_CR_SCLE;
+
+	/* enable master stop detected */
+	val |= SPACEMIT_CR_MSDE | SPACEMIT_CR_MSDIE;
+
+	writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static inline void
+spacemit_i2c_clear_int_status(struct spacemit_i2c_dev *i2c, u32 mask)
+{
+	writel(mask & SPACEMIT_I2C_INT_STATUS_MASK, i2c->base + SPACEMIT_ISR);
+}
+
+static void spacemit_i2c_start(struct spacemit_i2c_dev *i2c)
+{
+	u32 target_addr_rw, val;
+	struct i2c_msg *cur_msg = i2c->msgs + i2c->msg_idx;
+
+	i2c->read = !!(cur_msg->flags & I2C_M_RD);
+
+	i2c->state = SPACEMIT_STATE_START;
+
+	target_addr_rw = (cur_msg->addr & 0x7f) << 1;
+	if (cur_msg->flags & I2C_M_RD)
+		target_addr_rw |= 1;
+
+	writel(target_addr_rw, i2c->base + SPACEMIT_IDBR);
+
+	/* send start pulse */
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val &= ~SPACEMIT_CR_STOP;
+	val |= SPACEMIT_CR_START | SPACEMIT_CR_TB | SPACEMIT_CR_DTEIE;
+	writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_stop(struct spacemit_i2c_dev *i2c)
+{
+	u32 val;
+
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val |= SPACEMIT_CR_STOP | SPACEMIT_CR_ALDIE | SPACEMIT_CR_TB;
+
+	if (i2c->read)
+		val |= SPACEMIT_CR_ACKNAK;
+
+	writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
+{
+	unsigned long time_left;
+	struct i2c_msg *msg;
+
+	for (i2c->msg_idx = 0; i2c->msg_idx < i2c->msg_num; i2c->msg_idx++) {
+		msg = &i2c->msgs[i2c->msg_idx];
+		i2c->msg_buf = msg->buf;
+		i2c->unprocessed = msg->len;
+		i2c->status = 0;
+
+		reinit_completion(&i2c->complete);
+
+		spacemit_i2c_start(i2c);
+
+		time_left = wait_for_completion_timeout(&i2c->complete,
+							i2c->adapt.timeout);
+		if (!time_left) {
+			dev_err(i2c->dev, "msg completion timeout\n");
+			spacemit_i2c_conditionally_reset_bus(i2c);
+			spacemit_i2c_reset(i2c);
+			return -ETIMEDOUT;
+		}
+
+		if (i2c->status & SPACEMIT_SR_ERR)
+			return spacemit_i2c_handle_err(i2c);
+	}
+
+	return 0;
+}
+
+static bool spacemit_i2c_is_last_msg(struct spacemit_i2c_dev *i2c)
+{
+	if (i2c->msg_idx != i2c->msg_num - 1)
+		return false;
+
+	if (i2c->read)
+		return i2c->unprocessed == 1;
+
+	return !i2c->unprocessed;
+}
+
+static void spacemit_i2c_handle_write(struct spacemit_i2c_dev *i2c)
+{
+	/* if transfer completes, SPACEMIT_ISR will handle it */
+	if (i2c->status & SPACEMIT_SR_MSD)
+		return;
+
+	if (i2c->unprocessed) {
+		writel(*i2c->msg_buf++, i2c->base + SPACEMIT_IDBR);
+		i2c->unprocessed--;
+		return;
+	}
+
+	/* SPACEMIT_STATE_IDLE avoids trigger next byte */
+	i2c->state = SPACEMIT_STATE_IDLE;
+	complete(&i2c->complete);
+}
+
+static void spacemit_i2c_handle_read(struct spacemit_i2c_dev *i2c)
+{
+	if (i2c->unprocessed) {
+		*i2c->msg_buf++ = readl(i2c->base + SPACEMIT_IDBR);
+		i2c->unprocessed--;
+	}
+
+	/* if transfer completes, SPACEMIT_ISR will handle it */
+	if (i2c->status & (SPACEMIT_SR_MSD | SPACEMIT_SR_ACKNAK))
+		return;
+
+	/* it has to append stop bit in icr that read last byte */
+	if (i2c->unprocessed)
+		return;
+
+	/* SPACEMIT_STATE_IDLE avoids trigger next byte */
+	i2c->state = SPACEMIT_STATE_IDLE;
+	complete(&i2c->complete);
+}
+
+static void spacemit_i2c_handle_start(struct spacemit_i2c_dev *i2c)
+{
+	i2c->state = i2c->read ? SPACEMIT_STATE_READ : SPACEMIT_STATE_WRITE;
+	if (i2c->state == SPACEMIT_STATE_WRITE)
+		spacemit_i2c_handle_write(i2c);
+}
+
+static void spacemit_i2c_err_check(struct spacemit_i2c_dev *i2c)
+{
+	u32 val;
+
+	/*
+	 * Send transaction complete signal:
+	 * error happens, detect master stop
+	 */
+	if (!(i2c->status & (SPACEMIT_SR_ERR | SPACEMIT_SR_MSD)))
+		return;
+
+	/*
+	 * Here the transaction is already done, we don't need any
+	 * other interrupt signals from now, in case any interrupt
+	 * happens before spacemit_i2c_xfer to disable irq and i2c unit,
+	 * we mask all the interrupt signals and clear the interrupt
+	 * status.
+	 */
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val &= ~SPACEMIT_I2C_INT_CTRL_MASK;
+	writel(val, i2c->base + SPACEMIT_ICR);
+
+	spacemit_i2c_clear_int_status(i2c, SPACEMIT_I2C_INT_STATUS_MASK);
+
+	i2c->state = SPACEMIT_STATE_IDLE;
+	complete(&i2c->complete);
+}
+
+static irqreturn_t spacemit_i2c_irq_handler(int irq, void *devid)
+{
+	struct spacemit_i2c_dev *i2c = devid;
+	u32 status, val;
+
+	status = readl(i2c->base + SPACEMIT_ISR);
+	if (!status)
+		return IRQ_HANDLED;
+
+	i2c->status = status;
+
+	spacemit_i2c_clear_int_status(i2c, status);
+
+	if (i2c->status & SPACEMIT_SR_ERR)
+		goto err_out;
+
+	val = readl(i2c->base + SPACEMIT_ICR);
+	val &= ~(SPACEMIT_CR_TB | SPACEMIT_CR_ACKNAK | SPACEMIT_CR_STOP | SPACEMIT_CR_START);
+	writel(val, i2c->base + SPACEMIT_ICR);
+
+	switch (i2c->state) {
+	case SPACEMIT_STATE_START:
+		spacemit_i2c_handle_start(i2c);
+		break;
+	case SPACEMIT_STATE_READ:
+		spacemit_i2c_handle_read(i2c);
+		break;
+	case SPACEMIT_STATE_WRITE:
+		spacemit_i2c_handle_write(i2c);
+		break;
+	default:
+		break;
+	}
+
+	if (i2c->state != SPACEMIT_STATE_IDLE) {
+		if (spacemit_i2c_is_last_msg(i2c)) {
+			/* trigger next byte with stop */
+			spacemit_i2c_stop(i2c);
+		} else {
+			/* trigger next byte */
+			val |= SPACEMIT_CR_ALDIE | SPACEMIT_CR_TB;
+			writel(val, i2c->base + SPACEMIT_ICR);
+		}
+	}
+
+err_out:
+	spacemit_i2c_err_check(i2c);
+	return IRQ_HANDLED;
+}
+
+static void spacemit_i2c_calc_timeout(struct spacemit_i2c_dev *i2c)
+{
+	unsigned long timeout;
+	int idx = 0, cnt = 0;
+
+	for (; idx < i2c->msg_num; idx++)
+		cnt += (i2c->msgs + idx)->len + 1;
+
+	/*
+	 * Multiply by 9 because each byte in I2C transmission requires
+	 * 9 clock cycles: 8 bits of data plus 1 ACK/NACK bit.
+	 */
+	timeout = cnt * 9 * USEC_PER_SEC / i2c->clock_freq;
+
+	i2c->adapt.timeout = usecs_to_jiffies(timeout + USEC_PER_SEC / 10) / i2c->msg_num;
+}
+
+static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num)
+{
+	struct spacemit_i2c_dev *i2c = i2c_get_adapdata(adapt);
+	int ret;
+
+	i2c->msgs = msgs;
+	i2c->msg_num = num;
+
+	spacemit_i2c_calc_timeout(i2c);
+
+	spacemit_i2c_init(i2c);
+
+	spacemit_i2c_enable(i2c);
+
+	ret = spacemit_i2c_wait_bus_idle(i2c);
+	if (!ret)
+		spacemit_i2c_xfer_msg(i2c);
+	else if (ret < 0)
+		dev_dbg(i2c->dev, "i2c transfer error: %d\n", ret);
+	else
+		spacemit_i2c_check_bus_release(i2c);
+
+	spacemit_i2c_disable(i2c);
+
+	if (ret == -ETIMEDOUT || ret == -EAGAIN)
+		dev_err(i2c->dev, "i2c transfer failed, ret %d err 0x%lx\n",
+			  ret, i2c->status & SPACEMIT_SR_ERR);
+
+	return ret < 0 ? ret : num;
+}
+
+static u32 spacemit_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
+}
+
+static const struct i2c_algorithm spacemit_i2c_algo = {
+	.xfer = spacemit_i2c_xfer,
+	.functionality = spacemit_i2c_func,
+};
+
+static int spacemit_i2c_probe(struct platform_device *pdev)
+{
+	struct clk *clk;
+	struct device *dev = &pdev->dev;
+	struct device_node *of_node = pdev->dev.of_node;
+	struct spacemit_i2c_dev *i2c;
+	int ret;
+
+	i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	of_property_read_u32(of_node, "clock-frequency", &i2c->clock_freq);
+	if (ret && ret != -EINVAL)
+		dev_warn(dev, "failed to read clock-frequency property: %d\n", ret);
+
+	/* For now, this driver doesn't support high-speed. */
+	if (!i2c->clock_freq || i2c->clock_freq > SPACEMIT_I2C_MAX_FAST_MODE_FREQ) {
+		dev_warn(dev, "unsupported clock frequency %u; using %u\n",
+			 i2c->clock_freq, SPACEMIT_I2C_MAX_FAST_MODE_FREQ);
+		i2c->clock_freq = SPACEMIT_I2C_MAX_FAST_MODE_FREQ;
+	} else if (i2c->clock_freq < SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ) {
+		dev_warn(dev, "unsupported clock frequency %u; using %u\n",
+			 i2c->clock_freq,  SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ);
+		i2c->clock_freq = SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ;
+	}
+
+	i2c->dev = &pdev->dev;
+
+	i2c->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(i2c->base))
+		return dev_err_probe(dev, PTR_ERR(i2c->base), "failed to do ioremap");
+
+	i2c->irq = platform_get_irq(pdev, 0);
+	if (i2c->irq < 0)
+		return dev_err_probe(dev, i2c->irq, "failed to get irq resource");
+
+	ret = devm_request_irq(i2c->dev, i2c->irq, spacemit_i2c_irq_handler,
+			       IRQF_NO_SUSPEND | IRQF_ONESHOT, dev_name(i2c->dev), i2c);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to request irq");
+
+	clk = devm_clk_get_enabled(dev, "func");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable func clock");
+
+	clk = devm_clk_get_enabled(dev, "bus");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable bus clock");
+
+	spacemit_i2c_reset(i2c);
+
+	i2c_set_adapdata(&i2c->adapt, i2c);
+	i2c->adapt.owner = THIS_MODULE;
+	i2c->adapt.algo = &spacemit_i2c_algo;
+	i2c->adapt.dev.parent = i2c->dev;
+	i2c->adapt.nr = pdev->id;
+
+	i2c->adapt.dev.of_node = of_node;
+
+	strscpy(i2c->adapt.name, "spacemit-i2c-adapter", sizeof(i2c->adapt.name));
+
+	init_completion(&i2c->complete);
+
+	platform_set_drvdata(pdev, i2c);
+
+	ret = i2c_add_numbered_adapter(&i2c->adapt);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "failed to add i2c adapter");
+
+	return 0;
+}
+
+static void spacemit_i2c_remove(struct platform_device *pdev)
+{
+	struct spacemit_i2c_dev *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adapt);
+}
+
+static const struct of_device_id spacemit_i2c_of_match[] = {
+	{ .compatible = "spacemit,k1-i2c", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, spacemit_i2c_of_match);
+
+static struct platform_driver spacemit_i2c_driver = {
+	.probe = spacemit_i2c_probe,
+	.remove = spacemit_i2c_remove,
+	.driver = {
+		.name = "i2c-k1",
+		.of_match_table = spacemit_i2c_of_match,
+	},
+};
+module_platform_driver(spacemit_i2c_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("I2C bus driver for SpacemiT K1 SoC");

-- 
2.34.1

Re: [PATCH v8 2/2] i2c: spacemit: add support for SpacemiT K1 SoC

[Alex Elder]

On 3/19/25 4:29 AM, Troy Mitchell wrote:
> This patch introduces basic I2C support for the SpacemiT K1 SoC,
> utilizing interrupts for transfers.
> 
> The driver has been tested using i2c-tools on a Bananapi-F3 board,
> and basic I2C read/write operations have been confirmed to work.

So you removed support for the clock-frequency property, which
addresses both of the things I commented on in the last version.
This is great; I hope Andi is satisfied what anything else you
did and will merge this.

Nice work Troy.

					-Alex

> 
> Reviewed-by: Alex Elder <elder@riscstar.com>
> Link: https://lore.kernel.org/all/20250128-k1-maintainer-1-v1-1-e5dec4f379eb@gentoo.org [1]
> Signed-off-by: Troy Mitchell <troymitchell988@gmail.com>
> ---

. . .

Re: [PATCH v8 2/2] i2c: spacemit: add support for SpacemiT K1 SoC

[Andi Shyti]

Hi Troy,

On Wed, Mar 19, 2025 at 05:29:00PM +0800, Troy Mitchell wrote:
> This patch introduces basic I2C support for the SpacemiT K1 SoC,
> utilizing interrupts for transfers.
> 
> The driver has been tested using i2c-tools on a Bananapi-F3 board,
> and basic I2C read/write operations have been confirmed to work.
> 
> Reviewed-by: Alex Elder <elder@riscstar.com>
> Link: https://lore.kernel.org/all/20250128-k1-maintainer-1-v1-1-e5dec4f379eb@gentoo.org [1]

please, next time don't add the Link: tag here, I will add it
myself via b4. The link is not even correct.

I think this confuses b4 as well.

Anyway, I merged the two patches to i2c/i2c-host.

Thanks,
Andi