[PATCH v2] i2c: hisi: Add I2C bus recovery support

[PATCH v2] i2c: hisi: Add I2C bus recovery support

[Bowen Yu]

When the I2C bus is stuck due to a slave device holding SDA low
(e.g. during an incomplete transfer), the master has no way to recover
the bus through normal operation. Add bus recovery support using the
subctrl register to manually toggle SCL and generate clock pulses to
release the bus.

The recovery is performed via a second register resource (sctrl_base)
that provides direct control over SCL/SDA lines through mux and
output-enable bits. After recovery, the I2C controller is reset through
the ACPI _RST method and reconfigured.

Recovery is only registered when the subctrl resource is provided in
the firmware description, keeping backward compatibility with existing
platforms.

Signed-off-by: Bowen Yu <yubowen8@huawei.com>
---
v1 -> v2:
	-Guard all ACPI-specific calls and the recovery_init body with
	#ifdef CONFIG_ACPI.
---
 drivers/i2c/busses/i2c-hisi.c | 147 ++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)

diff --git a/drivers/i2c/busses/i2c-hisi.c b/drivers/i2c/busses/i2c-hisi.c
index ba5c9579ae19..ac69a2645d0b 100644
--- a/drivers/i2c/busses/i2c-hisi.c
+++ b/drivers/i2c/busses/i2c-hisi.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2021 HiSilicon Technologies Co., Ltd.
  */
 
+#include <linux/acpi.h>
 #include <linux/bits.h>
 #include <linux/bitfield.h>
 #include <linux/clk.h>
@@ -62,6 +63,8 @@
 #define HISI_I2C_INT_CLR		0x0048
 #define HISI_I2C_INT_MASK		0x004C
 #define HISI_I2C_TRANS_STATE		0x0050
+#define   HISI_I2C_TRANS_STATE_SDA_LEVEL	BIT(5)
+#define   HISI_I2C_TRANS_STATE_SCL_LEVEL	BIT(6)
 #define HISI_I2C_TRANS_ERR		0x0054
 #define HISI_I2C_VERSION		0x0058
 
@@ -86,9 +89,26 @@
 #define NSEC_TO_CYCLES(ns, clk_rate_khz) \
 	DIV_ROUND_UP_ULL((clk_rate_khz) * (ns), NSEC_PER_MSEC)
 
+/*
+ * SUBCTRL SC_I2C_CTRL register
+ * Set HISI_I2C_CTRL_DAT_CFG_EN and HISI_I2C_CTRL_SCL_CFG_EN to control
+ * I2C pin behavior by subctrl controller; use HISI_I2C_CTRL_DAT_OE and
+ * HISI_I2C_CTRL_CLK_OE to control input or output; use HISI_I2C_CTRL_SDA_OUT
+ * and HISI_I2C_CTRL_SCL_OUT to control output value.
+ */
+#define HISI_I2C_CTRL_DAT_CFG_EN BIT(5)
+#define HISI_I2C_CTRL_SCL_CFG_EN BIT(4)
+#define HISI_I2C_CTRL_DAT_OE BIT(3)
+#define HISI_I2C_CTRL_CLK_OE BIT(2)
+#define HISI_I2C_CTRL_SDA_OUT BIT(1)
+#define HISI_I2C_CTRL_SCL_OUT BIT(0)
+
+#define HISI_I2C_RECOVERY_REG_SIZE 4
+
 struct hisi_i2c_controller {
 	struct i2c_adapter adapter;
 	void __iomem *iobase;
+	void __iomem *sctrl_addr;
 	struct device *dev;
 	struct clk *clk;
 	int irq;
@@ -108,8 +128,14 @@ struct hisi_i2c_controller {
 	struct i2c_timings t;
 	u32 clk_rate_khz;
 	u32 spk_len;
+
+	/* Bus recovery */
+	struct i2c_bus_recovery_info rinfo;
+	acpi_handle acpi_handle;
 };
 
+static void hisi_i2c_configure_bus(struct hisi_i2c_controller *ctlr);
+
 static void hisi_i2c_enable_int(struct hisi_i2c_controller *ctlr, u32 mask)
 {
 	writel_relaxed(mask, ctlr->iobase + HISI_I2C_INT_MASK);
@@ -151,6 +177,123 @@ static void hisi_i2c_handle_errors(struct hisi_i2c_controller *ctlr)
 	}
 }
 
+static int hisi_i2c_recovery_get_scl(struct i2c_adapter *adap)
+{
+	struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
+	u32 reg = readl(ctlr->iobase + HISI_I2C_TRANS_STATE);
+
+	return !!(reg & HISI_I2C_TRANS_STATE_SCL_LEVEL);
+}
+
+static int hisi_i2c_recovery_get_sda(struct i2c_adapter *adap)
+{
+	struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
+	u32 reg = readl(ctlr->iobase + HISI_I2C_TRANS_STATE);
+
+	return !!(reg & HISI_I2C_TRANS_STATE_SDA_LEVEL);
+}
+
+static void hisi_i2c_recovery_set_scl(struct i2c_adapter *adap, int val)
+{
+	struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
+	u32 reg;
+
+	reg = readl(ctlr->sctrl_addr);
+	if (val)
+		reg |= HISI_I2C_CTRL_SCL_OUT;
+	else
+		reg &= ~HISI_I2C_CTRL_SCL_OUT;
+	writel(reg, ctlr->sctrl_addr);
+}
+
+static void hisi_i2c_prepare_recovery(struct i2c_adapter *adap)
+{
+	struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
+	u32 reg;
+
+	reg = readl(ctlr->sctrl_addr);
+	reg |= HISI_I2C_CTRL_SCL_CFG_EN | HISI_I2C_CTRL_DAT_CFG_EN |
+		   HISI_I2C_CTRL_CLK_OE | HISI_I2C_CTRL_SCL_OUT;
+	reg &= ~HISI_I2C_CTRL_DAT_OE;
+	writel(reg, ctlr->sctrl_addr);
+}
+
+static void hisi_i2c_unprepare_recovery(struct i2c_adapter *adap)
+{
+	struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
+	u32 reg;
+
+	reg = readl(ctlr->sctrl_addr);
+	reg &= ~(HISI_I2C_CTRL_SCL_CFG_EN | HISI_I2C_CTRL_DAT_CFG_EN);
+	writel(reg, ctlr->sctrl_addr);
+
+	/*
+	 * Invokes the specific ACPI method "_RST" to trigger a soft reset
+	 * of the I2C controller to help the I2C controller recover from
+	 * the abnormal state after the bus recovery process.
+	 */
+#ifdef CONFIG_ACPI
+	if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
+		acpi_status status;
+
+		status = acpi_evaluate_object(ctlr->acpi_handle, "_RST", NULL, NULL);
+		if (ACPI_FAILURE(status))
+			dev_err(ctlr->dev, "_RST method failed: %s\n",
+				acpi_format_exception(status));
+	}
+#endif
+	hisi_i2c_configure_bus(ctlr);
+}
+
+static int hisi_i2c_get_bus_recovery_res(struct hisi_i2c_controller *ctlr,
+					 struct platform_device *pdev)
+{
+	struct resource *res0;
+
+	res0 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+
+	if (!res0 || resource_size(res0) != HISI_I2C_RECOVERY_REG_SIZE)
+		return -ENODEV;
+
+	ctlr->sctrl_addr = devm_ioremap_resource(&pdev->dev, res0);
+	if (IS_ERR(ctlr->sctrl_addr)) {
+		ctlr->sctrl_addr = NULL;
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_ACPI
+static int hisi_i2c_recovery_init(struct hisi_i2c_controller *ctlr)
+{
+	struct platform_device *pdev = to_platform_device(ctlr->dev);
+	struct i2c_adapter *adapter = &ctlr->adapter;
+	int ret;
+
+	if (acpi_disabled)
+		return -ENODEV;
+
+	ret = hisi_i2c_get_bus_recovery_res(ctlr, pdev);
+	if (ret)
+		return ret;
+
+	ctlr->rinfo = (struct i2c_bus_recovery_info){
+		.get_scl = hisi_i2c_recovery_get_scl,
+		.get_sda = hisi_i2c_recovery_get_sda,
+		.set_scl = hisi_i2c_recovery_set_scl,
+		.prepare_recovery = hisi_i2c_prepare_recovery,
+		.unprepare_recovery = hisi_i2c_unprepare_recovery,
+		.recover_bus = i2c_generic_scl_recovery,
+	};
+	adapter->bus_recovery_info = &ctlr->rinfo;
+	ctlr->acpi_handle = ACPI_HANDLE(ctlr->dev);
+	return 0;
+}
+#else
+static int hisi_i2c_recovery_init(struct hisi_i2c_controller *ctlr) { return -ENODEV; }
+#endif /* CONFIG_ACPI */
+
 static int hisi_i2c_start_xfer(struct hisi_i2c_controller *ctlr)
 {
 	struct i2c_msg *msg = ctlr->msgs;
@@ -504,6 +647,10 @@ static int hisi_i2c_probe(struct platform_device *pdev)
 	adapter->dev.parent = dev;
 	i2c_set_adapdata(adapter, ctlr);
 
+	ret = hisi_i2c_recovery_init(ctlr);
+	if (ret)
+		dev_info(ctlr->dev, "I2C bus recovery not available\n");
+
 	ret = devm_i2c_add_adapter(dev, adapter);
 	if (ret)
 		return ret;
-- 
2.33.0

Re: [PATCH v2] i2c: hisi: Add I2C bus recovery support

[kernel test robot]

Hi Bowen,

kernel test robot noticed the following build warnings:

[auto build test WARNING on andi-shyti/i2c/i2c-host]
[also build test WARNING on linus/master v7.3-rc1 next-20260901]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Bowen-Yu/i2c-hisi-Add-I2C-bus-recovery-support/20260901-143116
base:   https://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git i2c/i2c-host
patch link:    https://lore.kernel.org/r/20260901063116.3438094-1-yubowen8%40huawei.com
patch subject: [PATCH v2] i2c: hisi: Add I2C bus recovery support
config: csky-randconfig-r064-20260902 (https://download.01.org/0day-ci/archive/20260902/202609021937.s2FqKDO3-lkp@intel.com/config)
compiler: csky-linux-gcc (GCC) 13.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260902/202609021937.s2FqKDO3-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609021937.s2FqKDO3-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/i2c/busses/i2c-hisi.c:249:12: warning: 'hisi_i2c_get_bus_recovery_res' defined but not used [-Wunused-function]
     249 | static int hisi_i2c_get_bus_recovery_res(struct hisi_i2c_controller *ctlr,
         |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/i2c/busses/i2c-hisi.c:222:13: warning: 'hisi_i2c_unprepare_recovery' defined but not used [-Wunused-function]
     222 | static void hisi_i2c_unprepare_recovery(struct i2c_adapter *adap)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/i2c/busses/i2c-hisi.c:210:13: warning: 'hisi_i2c_prepare_recovery' defined but not used [-Wunused-function]
     210 | static void hisi_i2c_prepare_recovery(struct i2c_adapter *adap)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/i2c/busses/i2c-hisi.c:197:13: warning: 'hisi_i2c_recovery_set_scl' defined but not used [-Wunused-function]
     197 | static void hisi_i2c_recovery_set_scl(struct i2c_adapter *adap, int val)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/i2c/busses/i2c-hisi.c:189:12: warning: 'hisi_i2c_recovery_get_sda' defined but not used [-Wunused-function]
     189 | static int hisi_i2c_recovery_get_sda(struct i2c_adapter *adap)
         |            ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/i2c/busses/i2c-hisi.c:181:12: warning: 'hisi_i2c_recovery_get_scl' defined but not used [-Wunused-function]
     181 | static int hisi_i2c_recovery_get_scl(struct i2c_adapter *adap)
         |            ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/hisi_i2c_get_bus_recovery_res +249 drivers/i2c/busses/i2c-hisi.c

   180	
 > 181	static int hisi_i2c_recovery_get_scl(struct i2c_adapter *adap)
   182	{
   183		struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
   184		u32 reg = readl(ctlr->iobase + HISI_I2C_TRANS_STATE);
   185	
   186		return !!(reg & HISI_I2C_TRANS_STATE_SCL_LEVEL);
   187	}
   188	
 > 189	static int hisi_i2c_recovery_get_sda(struct i2c_adapter *adap)
   190	{
   191		struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
   192		u32 reg = readl(ctlr->iobase + HISI_I2C_TRANS_STATE);
   193	
   194		return !!(reg & HISI_I2C_TRANS_STATE_SDA_LEVEL);
   195	}
   196	
 > 197	static void hisi_i2c_recovery_set_scl(struct i2c_adapter *adap, int val)
   198	{
   199		struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
   200		u32 reg;
   201	
   202		reg = readl(ctlr->sctrl_addr);
   203		if (val)
   204			reg |= HISI_I2C_CTRL_SCL_OUT;
   205		else
   206			reg &= ~HISI_I2C_CTRL_SCL_OUT;
   207		writel(reg, ctlr->sctrl_addr);
   208	}
   209	
 > 210	static void hisi_i2c_prepare_recovery(struct i2c_adapter *adap)
   211	{
   212		struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
   213		u32 reg;
   214	
   215		reg = readl(ctlr->sctrl_addr);
   216		reg |= HISI_I2C_CTRL_SCL_CFG_EN | HISI_I2C_CTRL_DAT_CFG_EN |
   217			   HISI_I2C_CTRL_CLK_OE | HISI_I2C_CTRL_SCL_OUT;
   218		reg &= ~HISI_I2C_CTRL_DAT_OE;
   219		writel(reg, ctlr->sctrl_addr);
   220	}
   221	
 > 222	static void hisi_i2c_unprepare_recovery(struct i2c_adapter *adap)
   223	{
   224		struct hisi_i2c_controller *ctlr = i2c_get_adapdata(adap);
   225		u32 reg;
   226	
   227		reg = readl(ctlr->sctrl_addr);
   228		reg &= ~(HISI_I2C_CTRL_SCL_CFG_EN | HISI_I2C_CTRL_DAT_CFG_EN);
   229		writel(reg, ctlr->sctrl_addr);
   230	
   231		/*
   232		 * Invokes the specific ACPI method "_RST" to trigger a soft reset
   233		 * of the I2C controller to help the I2C controller recover from
   234		 * the abnormal state after the bus recovery process.
   235		 */
   236	#ifdef CONFIG_ACPI
   237		if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
   238			acpi_status status;
   239	
   240			status = acpi_evaluate_object(ctlr->acpi_handle, "_RST", NULL, NULL);
   241			if (ACPI_FAILURE(status))
   242				dev_err(ctlr->dev, "_RST method failed: %s\n",
   243					acpi_format_exception(status));
   244		}
   245	#endif
   246		hisi_i2c_configure_bus(ctlr);
   247	}
   248	
 > 249	static int hisi_i2c_get_bus_recovery_res(struct hisi_i2c_controller *ctlr,
   250						 struct platform_device *pdev)
   251	{
   252		struct resource *res0;
   253	
   254		res0 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
   255	
   256		if (!res0 || resource_size(res0) != HISI_I2C_RECOVERY_REG_SIZE)
   257			return -ENODEV;
   258	
   259		ctlr->sctrl_addr = devm_ioremap_resource(&pdev->dev, res0);
   260		if (IS_ERR(ctlr->sctrl_addr)) {
   261			ctlr->sctrl_addr = NULL;
   262			return -ENOMEM;
   263		}
   264	
   265		return 0;
   266	}
   267	

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