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

[PATCH] 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>
---
 drivers/i2c/busses/i2c-hisi.c | 139 ++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)

diff --git a/drivers/i2c/busses/i2c-hisi.c b/drivers/i2c/busses/i2c-hisi.c
index 04d7978cae04..3f8e63be9f05 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 behaviorhe 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 +177,115 @@ 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" for trigger a soft
+	 * reset of I2C controller in order to help on I2C controller recover from
+	 * the abnormal state after bus recovery process.
+	 */
+	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));
+	}
+
+	hisi_i2c_configure_bus(ctlr);
+}
+
+static int hisi_i2c_get_bus_recovery_res(struct hisi_i2c_controller *ctlr,
+					 struct platform_device *pdev)
+{
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+
+	if (!res || resource_size(res) != HISI_I2C_RECOVERY_REG_SIZE)
+		return -ENODEV;
+
+	ctlr->sctrl_addr = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(ctlr->sctrl_addr)) {
+		ctlr->sctrl_addr = NULL;
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+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;
+
+	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;
+}
+
 static int hisi_i2c_start_xfer(struct hisi_i2c_controller *ctlr)
 {
 	struct i2c_msg *msg = ctlr->msgs;
@@ -504,6 +639,10 @@ 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] i2c: hisi: Add I2C bus recovery support

[kernel test robot]

Hi Bowen,

kernel test robot noticed the following build errors:

[auto build test ERROR on andi-shyti/i2c/i2c-host]
[also build test ERROR on linus/master v7.2 next-20260824]
[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/20260825-113125
base:   https://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git i2c/i2c-host
patch link:    https://lore.kernel.org/r/20260825033125.1893253-1-yubowen8%40huawei.com
patch subject: [PATCH] i2c: hisi: Add I2C bus recovery support
config: nios2-allmodconfig (https://download.01.org/0day-ci/archive/20260826/202608260721.whmqyiAk-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260826/202608260721.whmqyiAk-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/202608260721.whmqyiAk-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/i2c/busses/i2c-hisi.c: In function 'hisi_i2c_unprepare_recovery':
>> drivers/i2c/busses/i2c-hisi.c:236:34: error: implicit declaration of function 'acpi_has_method'; did you mean 'acpi_has_watchdog'? [-Werror=implicit-function-declaration]
     236 |         if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
         |                                  ^~~~~~~~~~~~~~~
         |                                  acpi_has_watchdog
   In file included from include/linux/device.h:15,
                    from include/linux/acpi.h:15,
                    from drivers/i2c/busses/i2c-hisi.c:8:
   include/linux/dev_printk.h:154:31: warning: '%s' directive argument is null [-Wformat-overflow=]
     154 |         dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
         |                               ^
   include/linux/dev_printk.h:110:17: note: in definition of macro 'dev_printk_index_wrap'
     110 |                 _p_func(dev, fmt, ##__VA_ARGS__);                       \
         |                 ^~~~~~~
   drivers/i2c/busses/i2c-hisi.c:241:25: note: in expansion of macro 'dev_err'
     241 |                         dev_err(ctlr->dev, "_RST method failed: %s\n",
         |                         ^~~~~~~
   drivers/i2c/busses/i2c-hisi.c:241:65: note: format string is defined here
     241 |                         dev_err(ctlr->dev, "_RST method failed: %s\n",
         |                                                                 ^~
   cc1: some warnings being treated as errors


vim +236 drivers/i2c/busses/i2c-hisi.c

   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" for trigger a soft
   233		 * reset of I2C controller in order to help on I2C controller recover from
   234		 * the abnormal state after bus recovery process.
   235		 */
 > 236		if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
   237			acpi_status status;
   238	
   239			status = acpi_evaluate_object(ctlr->acpi_handle, "_RST", NULL, NULL);
   240			if (ACPI_FAILURE(status))
   241				dev_err(ctlr->dev, "_RST method failed: %s\n",
   242					acpi_format_exception(status));
   243		}
   244	
   245		hisi_i2c_configure_bus(ctlr);
   246	}
   247	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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

[kernel test robot]

Hi Bowen,

kernel test robot noticed the following build errors:

[auto build test ERROR on andi-shyti/i2c/i2c-host]
[also build test ERROR on linus/master v7.2 next-20260824]
[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/20260825-113125
base:   https://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git i2c/i2c-host
patch link:    https://lore.kernel.org/r/20260825033125.1893253-1-yubowen8%40huawei.com
patch subject: [PATCH] i2c: hisi: Add I2C bus recovery support
config: arm-randconfig-003-20260826 (https://download.01.org/0day-ci/archive/20260826/202608260816.YagBXzlX-lkp@intel.com/config)
compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 771bdfdab2d66a4eb85b8ea7673cfa30152718b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260826/202608260816.YagBXzlX-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/202608260816.YagBXzlX-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/i2c/busses/i2c-hisi.c:236:27: error: call to undeclared function 'acpi_has_method'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     236 |         if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
         |                                  ^
   drivers/i2c/busses/i2c-hisi.c:236:27: note: did you mean 'acpi_has_watchdog'?
   include/linux/acpi.h:1528:20: note: 'acpi_has_watchdog' declared here
    1528 | static inline bool acpi_has_watchdog(void) { return false; }
         |                    ^
   1 error generated.


vim +/acpi_has_method +236 drivers/i2c/busses/i2c-hisi.c

   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" for trigger a soft
   233		 * reset of I2C controller in order to help on I2C controller recover from
   234		 * the abnormal state after bus recovery process.
   235		 */
 > 236		if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
   237			acpi_status status;
   238	
   239			status = acpi_evaluate_object(ctlr->acpi_handle, "_RST", NULL, NULL);
   240			if (ACPI_FAILURE(status))
   241				dev_err(ctlr->dev, "_RST method failed: %s\n",
   242					acpi_format_exception(status));
   243		}
   244	
   245		hisi_i2c_configure_bus(ctlr);
   246	}
   247	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] 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 v7.2 next-20260824]
[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/20260825-113125
base:   https://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git i2c/i2c-host
patch link:    https://lore.kernel.org/r/20260825033125.1893253-1-yubowen8%40huawei.com
patch subject: [PATCH] i2c: hisi: Add I2C bus recovery support
config: sparc64-randconfig-001-20260826 (https://download.01.org/0day-ci/archive/20260826/202608260844.RKBd2Emp-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 13.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260826/202608260844.RKBd2Emp-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/202608260844.RKBd2Emp-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/i2c/busses/i2c-hisi.c: In function 'hisi_i2c_unprepare_recovery':
   drivers/i2c/busses/i2c-hisi.c:236:34: error: implicit declaration of function 'acpi_has_method'; did you mean 'acpi_has_watchdog'? [-Werror=implicit-function-declaration]
     236 |         if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
         |                                  ^~~~~~~~~~~~~~~
         |                                  acpi_has_watchdog
   In file included from include/linux/device.h:15,
                    from include/linux/acpi.h:15,
                    from drivers/i2c/busses/i2c-hisi.c:8:
>> drivers/i2c/busses/i2c-hisi.c:241:44: warning: '%s' directive argument is null [-Wformat-overflow=]
     241 |                         dev_err(ctlr->dev, "_RST method failed: %s\n",
         |                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/dev_printk.h:110:30: note: in definition of macro 'dev_printk_index_wrap'
     110 |                 _p_func(dev, fmt, ##__VA_ARGS__);                       \
         |                              ^~~
   include/linux/dev_printk.h:154:56: note: in expansion of macro 'dev_fmt'
     154 |         dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
         |                                                        ^~~~~~~
   drivers/i2c/busses/i2c-hisi.c:241:25: note: in expansion of macro 'dev_err'
     241 |                         dev_err(ctlr->dev, "_RST method failed: %s\n",
         |                         ^~~~~~~
   drivers/i2c/busses/i2c-hisi.c:241:65: note: format string is defined here
     241 |                         dev_err(ctlr->dev, "_RST method failed: %s\n",
         |                                                                 ^~
   cc1: some warnings being treated as errors


vim +241 drivers/i2c/busses/i2c-hisi.c

   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" for trigger a soft
   233		 * reset of I2C controller in order to help on I2C controller recover from
   234		 * the abnormal state after bus recovery process.
   235		 */
   236		if (ctlr->acpi_handle && acpi_has_method(ctlr->acpi_handle, "_RST")) {
   237			acpi_status status;
   238	
   239			status = acpi_evaluate_object(ctlr->acpi_handle, "_RST", NULL, NULL);
   240			if (ACPI_FAILURE(status))
 > 241				dev_err(ctlr->dev, "_RST method failed: %s\n",
   242					acpi_format_exception(status));
   243		}
   244	
   245		hisi_i2c_configure_bus(ctlr);
   246	}
   247	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki