Add support for the I2C controller on the RTL9300 SoC. There are two I2C
controllers in the RTL9300 that are part of the Ethernet switch register
block. Each of these controllers owns a SCL pin (GPIO8 for the fiorst
I2C controller, GPIO17 for the second). There are 8 possible SDA pins
(GPIO9-16) that can be assigned to either I2C controller. This
relationship is represented in the device tree with a child node for
each SDA line in use.

This is based on the openwrt implementation[1] but has been
significantly modified

[1] - https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=target/linux/realtek/files-5.15/drivers/i2c/busses/i2c-rtl9300.c

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
    Changes in v5:
    - Make lock part of struct rtl9300_i2c
    - Fix alignment in rtl9300_i2c_smbus_xfer
    Changes in v4:
    - skipped due to combining patch series
    Changes in v3:
    - None
    Changes in v2:
    - Replace a number of return 0; with tail calls
    - Add enum rtl9300_bus_freq
    - Use RTL9300_ prefix on new defines
    - Use reg property for register offset
    - Hard code RTL9300_I2C_MST_GLB_CTRL address as this does not need to
      come from DT binding
    - Use GENMASK() where appropriate
    - Propagate read/write errors through to rtl9300_i2c_smbus_xfer()
    - Don't error out on bad clock-frequency
    - Use devm_i2c_add_adapter()
    - Put more information in the commit message
    - Integrated multiplexing function, an adapter is created per SDA line

 MAINTAINERS                      |   7 +
 drivers/i2c/busses/Kconfig       |  10 +
 drivers/i2c/busses/Makefile      |   1 +
 drivers/i2c/busses/i2c-rtl9300.c | 422 +++++++++++++++++++++++++++++++
 4 files changed, 440 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-rtl9300.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f328373463b0..9e123e9839a5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19887,6 +19887,13 @@ S:	Maintained
 T:	git https://github.com/pkshih/rtw.git
 F:	drivers/net/wireless/realtek/rtl8xxxu/
 
+RTL9300 I2C DRIVER (rtl9300-i2c)
+M:	Chris Packham <chris.packham@alliedtelesis.co.nz>
+L:	linux-i2c@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
+F:	drivers/i2c/busses/i2c-rtl9300.c
+
 RTRS TRANSPORT DRIVERS
 M:	Md. Haris Iqbal <haris.iqbal@ionos.com>
 M:	Jack Wang <jinpu.wang@ionos.com>
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index a22f9125322a..927b583002c7 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -1041,6 +1041,16 @@ config I2C_RK3X
 	  This driver can also be built as a module. If so, the module will
 	  be called i2c-rk3x.
 
+config I2C_RTL9300
+	tristate "Realtek RTL9300 I2C controller"
+	depends on MACH_REALTEK_RTL || COMPILE_TEST
+	help
+	  Say Y here to include support for the I2C controller in Realtek
+	  RTL9300 SoCs.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called i2c-rtl9300.
+
 config I2C_RZV2M
 	tristate "Renesas RZ/V2M adapter"
 	depends on ARCH_RENESAS || COMPILE_TEST
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 78d0561339e5..ac2f9f22803c 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -102,6 +102,7 @@ obj-$(CONFIG_I2C_QCOM_GENI)	+= i2c-qcom-geni.o
 obj-$(CONFIG_I2C_QUP)		+= i2c-qup.o
 obj-$(CONFIG_I2C_RIIC)		+= i2c-riic.o
 obj-$(CONFIG_I2C_RK3X)		+= i2c-rk3x.o
+obj-$(CONFIG_I2C_RTL9300)	+= i2c-rtl9300.o
 obj-$(CONFIG_I2C_RZV2M)		+= i2c-rzv2m.o
 obj-$(CONFIG_I2C_S3C2410)	+= i2c-s3c2410.o
 obj-$(CONFIG_I2C_SH7760)	+= i2c-sh7760.o
diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
new file mode 100644
index 000000000000..ed9a45a9d803
--- /dev/null
+++ b/drivers/i2c/busses/i2c-rtl9300.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mfd/syscon.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+enum rtl9300_bus_freq {
+	RTL9300_I2C_STD_FREQ,
+	RTL9300_I2C_FAST_FREQ,
+};
+
+struct rtl9300_i2c;
+
+struct rtl9300_i2c_chan {
+	struct i2c_adapter adap;
+	struct rtl9300_i2c *i2c;
+	enum rtl9300_bus_freq bus_freq;
+	u8 sda_pin;
+};
+
+#define RTL9300_I2C_MUX_NCHAN	8
+
+struct rtl9300_i2c {
+	struct regmap *regmap;
+	struct device *dev;
+	struct rtl9300_i2c_chan chans[RTL9300_I2C_MUX_NCHAN];
+	u32 reg_base;
+	u8 sda_pin;
+	struct mutex lock;
+};
+
+#define RTL9300_I2C_MST_CTRL1			0x0
+#define  RTL9300_I2C_MST_CTRL1_MEM_ADDR_OFS	8
+#define  RTL9300_I2C_MST_CTRL1_MEM_ADDR_MASK	GENMASK(31, 8)
+#define  RTL9300_I2C_MST_CTRL1_SDA_OUT_SEL_OFS	4
+#define  RTL9300_I2C_MST_CTRL1_SDA_OUT_SEL_MASK	GENMASK(6, 4)
+#define  RTL9300_I2C_MST_CTRL1_GPIO_SCL_SEL	BIT(3)
+#define  RTL9300_I2C_MST_CTRL1_RWOP		BIT(2)
+#define  RTL9300_I2C_MST_CTRL1_I2C_FAIL		BIT(1)
+#define  RTL9300_I2C_MST_CTRL1_I2C_TRIG		BIT(0)
+#define RTL9300_I2C_MST_CTRL2			0x4
+#define  RTL9300_I2C_MST_CTRL2_RD_MODE		BIT(15)
+#define  RTL9300_I2C_MST_CTRL2_DEV_ADDR_OFS	8
+#define  RTL9300_I2C_MST_CTRL2_DEV_ADDR_MASK	GENMASK(14, 8)
+#define  RTL9300_I2C_MST_CTRL2_DATA_WIDTH_OFS	4
+#define  RTL9300_I2C_MST_CTRL2_DATA_WIDTH_MASK	GENMASK(7, 4)
+#define  RTL9300_I2C_MST_CTRL2_MEM_ADDR_WIDTH_OFS	2
+#define  RTL9300_I2C_MST_CTRL2_MEM_ADDR_WIDTH_MASK	GENMASK(3, 2)
+#define  RTL9300_I2C_MST_CTRL2_SCL_FREQ_OFS	0
+#define  RTL9300_I2C_MST_CTRL2_SCL_FREQ_MASK	GENMASK(1, 0)
+#define RTL9300_I2C_MST_DATA_WORD0		0x8
+#define RTL9300_I2C_MST_DATA_WORD1		0xc
+#define RTL9300_I2C_MST_DATA_WORD2		0x10
+#define RTL9300_I2C_MST_DATA_WORD3		0x14
+
+#define RTL9300_I2C_MST_GLB_CTRL  0x384
+
+static int rtl9300_i2c_reg_addr_set(struct rtl9300_i2c *i2c, u32 reg, u16 len)
+{
+	u32 val, mask;
+	int ret;
+
+	val = len << RTL9300_I2C_MST_CTRL2_MEM_ADDR_WIDTH_OFS;
+	mask = RTL9300_I2C_MST_CTRL2_MEM_ADDR_WIDTH_MASK;
+
+	ret = regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL2, mask, val);
+	if (ret)
+		return ret;
+
+	val = reg << RTL9300_I2C_MST_CTRL1_MEM_ADDR_OFS;
+	mask = RTL9300_I2C_MST_CTRL1_MEM_ADDR_MASK;
+
+	return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+}
+
+static int rtl9300_i2c_config_io(struct rtl9300_i2c *i2c, u8 sda_pin)
+{
+	int ret;
+	u32 val, mask;
+
+	ret = regmap_update_bits(i2c->regmap, RTL9300_I2C_MST_GLB_CTRL, BIT(sda_pin), BIT(sda_pin));
+	if (ret)
+		return ret;
+
+	val = (sda_pin << RTL9300_I2C_MST_CTRL1_SDA_OUT_SEL_OFS) |
+		RTL9300_I2C_MST_CTRL1_GPIO_SCL_SEL;
+	mask = RTL9300_I2C_MST_CTRL1_SDA_OUT_SEL_MASK | RTL9300_I2C_MST_CTRL1_GPIO_SCL_SEL;
+
+	return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+}
+
+static int rtl9300_i2c_config_xfer(struct rtl9300_i2c *i2c, struct rtl9300_i2c_chan *chan,
+				   u16 addr, u16 len)
+{
+	u32 val, mask;
+
+	val = chan->bus_freq << RTL9300_I2C_MST_CTRL2_SCL_FREQ_OFS;
+	mask = RTL9300_I2C_MST_CTRL2_SCL_FREQ_MASK;
+
+	val |= addr << RTL9300_I2C_MST_CTRL2_DEV_ADDR_OFS;
+	mask |= RTL9300_I2C_MST_CTRL2_DEV_ADDR_MASK;
+
+	val |= ((len - 1) & 0xf) << RTL9300_I2C_MST_CTRL2_DATA_WIDTH_OFS;
+	mask |= RTL9300_I2C_MST_CTRL2_DATA_WIDTH_MASK;
+
+	mask |= RTL9300_I2C_MST_CTRL2_RD_MODE;
+
+	return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL2, mask, val);
+}
+
+static int rtl9300_i2c_read(struct rtl9300_i2c *i2c, u8 *buf, int len)
+{
+	u32 vals[4] = {};
+	int i, ret;
+
+	if (len > 16)
+		return -EIO;
+
+	ret = regmap_bulk_read(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0,
+			       vals, ARRAY_SIZE(vals));
+	if (ret)
+		return ret;
+
+	for (i = 0; i < len; i++) {
+		buf[i] = vals[i/4] & 0xff;
+		vals[i/4] >>= 8;
+	}
+
+	return 0;
+}
+
+static int rtl9300_i2c_write(struct rtl9300_i2c *i2c, u8 *buf, int len)
+{
+	u32 vals[4] = {};
+	int i;
+
+	if (len > 16)
+		return -EIO;
+
+	for (i = 0; i < len; i++) {
+		if (i % 4 == 0)
+			vals[i/4] = 0;
+		vals[i/4] <<= 8;
+		vals[i/4] |= buf[i];
+	}
+
+	return regmap_bulk_write(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0,
+				vals, ARRAY_SIZE(vals));
+}
+
+static int rtl9300_i2c_writel(struct rtl9300_i2c *i2c, u32 data)
+{
+	return regmap_write(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0, data);
+}
+
+static int rtl9300_i2c_execute_xfer(struct rtl9300_i2c *i2c, char read_write,
+				int size, union i2c_smbus_data *data, int len)
+{
+	u32 val, mask;
+	int ret;
+
+	val = read_write == I2C_SMBUS_WRITE ? RTL9300_I2C_MST_CTRL1_RWOP : 0;
+	mask = RTL9300_I2C_MST_CTRL1_RWOP;
+
+	val |= RTL9300_I2C_MST_CTRL1_I2C_TRIG;
+	mask |= RTL9300_I2C_MST_CTRL1_I2C_TRIG;
+
+	ret = regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+	if (ret)
+		return ret;
+
+	ret = regmap_read_poll_timeout(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1,
+				       val, !(val & RTL9300_I2C_MST_CTRL1_I2C_TRIG), 100, 2000);
+	if (ret)
+		return ret;
+
+	if (val & RTL9300_I2C_MST_CTRL1_I2C_FAIL)
+		return -EIO;
+
+	if (read_write == I2C_SMBUS_READ) {
+		if (size == I2C_SMBUS_BYTE || size == I2C_SMBUS_BYTE_DATA) {
+			ret = regmap_read(i2c->regmap,
+					  i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0, &val);
+			if (ret)
+				return ret;
+			data->byte = val & 0xff;
+		} else if (size == I2C_SMBUS_WORD_DATA) {
+			ret = regmap_read(i2c->regmap,
+					  i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0, &val);
+			if (ret)
+				return ret;
+			data->word = val & 0xffff;
+		} else {
+			ret = rtl9300_i2c_read(i2c, &data->block[0], len);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
+static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
+				  char read_write, u8 command, int size,
+				  union i2c_smbus_data *data)
+{
+	struct rtl9300_i2c_chan *chan = i2c_get_adapdata(adap);
+	struct rtl9300_i2c *i2c = chan->i2c;
+	int len = 0, ret;
+
+	mutex_lock(&i2c->lock);
+	if (chan->sda_pin != i2c->sda_pin) {
+		ret = rtl9300_i2c_config_io(i2c, chan->sda_pin);
+		if (ret)
+			goto out_unlock;
+		i2c->sda_pin = chan->sda_pin;
+	}
+
+	switch (size) {
+	case I2C_SMBUS_QUICK:
+		ret = rtl9300_i2c_config_xfer(i2c, chan, addr, 0);
+		if (ret)
+			goto out_unlock;
+		ret = rtl9300_i2c_reg_addr_set(i2c, 0, 0);
+		if (ret)
+			goto out_unlock;
+		break;
+
+	case I2C_SMBUS_BYTE:
+		if (read_write == I2C_SMBUS_WRITE) {
+			ret = rtl9300_i2c_config_xfer(i2c, chan, addr, 0);
+			if (ret)
+				goto out_unlock;
+			ret = rtl9300_i2c_reg_addr_set(i2c, command, 1);
+			if (ret)
+				goto out_unlock;
+		} else {
+			ret = rtl9300_i2c_config_xfer(i2c, chan, addr, 1);
+			if (ret)
+				goto out_unlock;
+			ret = rtl9300_i2c_reg_addr_set(i2c, 0, 0);
+			if (ret)
+				goto out_unlock;
+		}
+		break;
+
+	case I2C_SMBUS_BYTE_DATA:
+		ret = rtl9300_i2c_reg_addr_set(i2c, command, 1);
+		if (ret)
+			goto out_unlock;
+		ret = rtl9300_i2c_config_xfer(i2c, chan, addr, 1);
+		if (ret)
+			goto out_unlock;
+		if (read_write == I2C_SMBUS_WRITE) {
+			ret = rtl9300_i2c_writel(i2c, data->byte);
+			if (ret)
+				goto out_unlock;
+		}
+		break;
+
+	case I2C_SMBUS_WORD_DATA:
+		ret = rtl9300_i2c_reg_addr_set(i2c, command, 1);
+		if (ret)
+			goto out_unlock;
+		ret = rtl9300_i2c_config_xfer(i2c, chan, addr, 2);
+		if (ret)
+			goto out_unlock;
+		if (read_write == I2C_SMBUS_WRITE) {
+			ret = rtl9300_i2c_writel(i2c, data->word);
+			if (ret)
+				goto out_unlock;
+		}
+		break;
+
+	case I2C_SMBUS_BLOCK_DATA:
+		ret = rtl9300_i2c_reg_addr_set(i2c, command, 1);
+		if (ret)
+			goto out_unlock;
+		ret = rtl9300_i2c_config_xfer(i2c, chan, addr, data->block[0]);
+		if (ret)
+			goto out_unlock;
+		if (read_write == I2C_SMBUS_WRITE) {
+			ret = rtl9300_i2c_write(i2c, &data->block[1], data->block[0]);
+			if (ret)
+				goto out_unlock;
+		}
+		len = data->block[0];
+		break;
+
+	default:
+		dev_err(&adap->dev, "Unsupported transaction %d\n", size);
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+
+	ret = rtl9300_i2c_execute_xfer(i2c, read_write, size, data, len);
+
+out_unlock:
+	mutex_unlock(&i2c->lock);
+
+	return ret;
+}
+
+static u32 rtl9300_i2c_func(struct i2c_adapter *a)
+{
+	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
+	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
+	       I2C_FUNC_SMBUS_BLOCK_DATA;
+}
+
+static const struct i2c_algorithm rtl9300_i2c_algo = {
+	.smbus_xfer	= rtl9300_i2c_smbus_xfer,
+	.functionality	= rtl9300_i2c_func,
+};
+
+struct i2c_adapter_quirks rtl9300_i2c_quirks = {
+	.flags		= I2C_AQ_NO_CLK_STRETCH,
+	.max_read_len	= 16,
+	.max_write_len	= 16,
+};
+
+static int rtl9300_i2c_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rtl9300_i2c_chan *chan;
+	struct rtl9300_i2c *i2c;
+	struct i2c_adapter *adap;
+	u32 clock_freq, sda_pin;
+	int ret, i = 0;
+	struct fwnode_handle *child;
+
+	i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->regmap = syscon_node_to_regmap(dev->parent->of_node);
+	if (IS_ERR(i2c->regmap))
+		return PTR_ERR(i2c->regmap);
+	i2c->dev = dev;
+
+	mutex_init(&i2c->lock);
+
+	ret = device_property_read_u32(dev, "reg", &i2c->reg_base);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, i2c);
+
+	if (device_get_child_node_count(dev) >= RTL9300_I2C_MUX_NCHAN)
+		return dev_err_probe(dev, -EINVAL, "Too many channels\n");
+
+	device_for_each_child_node(dev, child) {
+		chan = &i2c->chans[i];
+		adap = &chan->adap;
+
+		ret = fwnode_property_read_u32(child, "reg", &sda_pin);
+		if (ret)
+			return ret;
+
+		ret = fwnode_property_read_u32(child, "clock-frequency", &clock_freq);
+		if (ret)
+			clock_freq = I2C_MAX_STANDARD_MODE_FREQ;
+
+		switch (clock_freq) {
+		case I2C_MAX_STANDARD_MODE_FREQ:
+			chan->bus_freq = RTL9300_I2C_STD_FREQ;
+			break;
+
+		case I2C_MAX_FAST_MODE_FREQ:
+			chan->bus_freq = RTL9300_I2C_FAST_FREQ;
+			break;
+		default:
+			dev_warn(i2c->dev, "SDA%d clock-frequency %d not supported using default\n",
+				 sda_pin, clock_freq);
+			break;
+		}
+
+		chan->sda_pin = sda_pin;
+		chan->i2c = i2c;
+		adap = &i2c->chans[i].adap;
+		adap->owner = THIS_MODULE;
+		adap->algo = &rtl9300_i2c_algo;
+		adap->quirks = &rtl9300_i2c_quirks;
+		adap->retries = 3;
+		adap->dev.parent = dev;
+		i2c_set_adapdata(adap, chan);
+		adap->dev.of_node = to_of_node(child);
+		snprintf(adap->name, sizeof(adap->name), "%s SDA%d\n", dev_name(dev), sda_pin);
+		i++;
+
+		ret = devm_i2c_add_adapter(dev, adap);
+		if (ret)
+			return ret;
+	}
+	i2c->sda_pin = 0xff;
+
+	return 0;
+}
+
+static const struct of_device_id i2c_rtl9300_dt_ids[] = {
+	{ .compatible = "realtek,rtl9300-i2c" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, i2c_rtl9300_dt_ids);
+
+static struct platform_driver rtl9300_i2c_driver = {
+	.probe = rtl9300_i2c_probe,
+	.driver = {
+		.name = "i2c-rtl9300",
+		.of_match_table = i2c_rtl9300_dt_ids,
+	},
+};
+
+module_platform_driver(rtl9300_i2c_driver);
+
+MODULE_DESCRIPTION("RTL9300 I2C controller driver");
+MODULE_LICENSE("GPL");
-- 
2.46.2

…
> +++ b/drivers/i2c/busses/i2c-rtl9300.c
> @@ -0,0 +1,422 @@
…
> +static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
> +				  char read_write, u8 command, int size,
> +				  union i2c_smbus_data *data)
> +{
…
> +	mutex_lock(&i2c->lock);
> +	if (chan->sda_pin != i2c->sda_pin) {
…
> +out_unlock:
> +	mutex_unlock(&i2c->lock);
> +
> +	return ret;
> +}
…

Under which circumstances would you become interested to apply a statement
like “guard(mutex)(&i2c->lock);”?
https://elixir.bootlin.com/linux/v6.11/source/include/linux/mutex.h#L196

Regards,
Markus

Hi Markus,

On 29/09/24 21:45, Markus Elfring wrote:
> …
>> +++ b/drivers/i2c/busses/i2c-rtl9300.c
>> @@ -0,0 +1,422 @@
> …
>> +static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
>> +				  char read_write, u8 command, int size,
>> +				  union i2c_smbus_data *data)
>> +{
> …
>> +	mutex_lock(&i2c->lock);
>> +	if (chan->sda_pin != i2c->sda_pin) {
> …
>> +out_unlock:
>> +	mutex_unlock(&i2c->lock);
>> +
>> +	return ret;
>> +}
> …
>
> Under which circumstances would you become interested to apply a statement
> like “guard(mutex)(&i2c->lock);”?
> https://elixir.bootlin.com/linux/v6.11/source/include/linux/mutex.h#L196

At this stage I don't what to change unless Andi insists that I do.

I can't find much mention of using guard() on 
https://www.kernel.org/doc/html/latest/ but I can see enough examples 
(although notably none in drivers/i2c) that I _think_ I can see how I 
could use it.

>> …
>>> +++ b/drivers/i2c/busses/i2c-rtl9300.c
>>> @@ -0,0 +1,422 @@
>> …
>>> +static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
>>> +                  char read_write, u8 command, int size,
>>> +                  union i2c_smbus_data *data)
>>> +{
>> …
>>> +    mutex_lock(&i2c->lock);
>>> +    if (chan->sda_pin != i2c->sda_pin) {
>> …
>>> +out_unlock:
>>> +    mutex_unlock(&i2c->lock);
>>> +
>>> +    return ret;
>>> +}
>> …
>>
>> Under which circumstances would you become interested to apply a statement
>> like “guard(mutex)(&i2c->lock);”?
>> https://elixir.bootlin.com/linux/v6.11/source/include/linux/mutex.h#L196
>
> At this stage I don't what to change unless Andi insists that I do.
>
> I can't find much mention of using guard() on https://www.kernel.org/doc/html/latest/

Do you find any other information sources more encouraging?


> but I can see enough examples (although notably none in drivers/i2c) that I _think_ I can see how I could use it.

See also (for example):
Article “Linux Kernel Development - Automatic Cleanup”
by Javier Carrasco Cruz
2024-06-17
https://javiercarrascocruz.github.io/kernel-auto-cleanup-2#2-automatic-mutex-handling

Regards,
Markus

On 30/09/2024 09:55, Markus Elfring wrote:
>>> …
>>>> +++ b/drivers/i2c/busses/i2c-rtl9300.c
>>>> @@ -0,0 +1,422 @@
>>> …
>>>> +static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
>>>> +                  char read_write, u8 command, int size,
>>>> +                  union i2c_smbus_data *data)
>>>> +{
>>> …
>>>> +    mutex_lock(&i2c->lock);
>>>> +    if (chan->sda_pin != i2c->sda_pin) {
>>> …
>>>> +out_unlock:
>>>> +    mutex_unlock(&i2c->lock);
>>>> +
>>>> +    return ret;
>>>> +}
>>> …
>>>
>>> Under which circumstances would you become interested to apply a statement
>>> like “guard(mutex)(&i2c->lock);”?
>>> https://elixir.bootlin.com/linux/v6.11/source/include/linux/mutex.h#L196
>>
>> At this stage I don't what to change unless Andi insists that I do.
>>
>> I can't find much mention of using guard() on https://www.kernel.org/doc/html/latest/
> 
> Do you find any other information sources more encouraging?
> 
> 
>> but I can see enough examples (although notably none in drivers/i2c) that I _think_ I can see how I could use it.
> 
> See also (for example):
> Article “Linux Kernel Development - Automatic Cleanup”
> by Javier Carrasco Cruz
> 2024-06-17
> https://javiercarrascocruz.github.io/kernel-auto-cleanup-2#2-automatic-mutex-handling
> 
> Regards,
> Markus

My personal blog is definitely NOT an official or even reliable source
of information.

Thanks for referencing it, but please look for examples of guard() in
the kernel, because there are several examples for different kind of
mutexes. For example, IIO uses them widely. And they are really nice, so
I would recommend anyone using them whenever it makes sense.

Best regards,
Javier Carrasco

Hi Chris,

kernel test robot noticed the following build warnings:

[auto build test WARNING on robh/for-next]
[also build test WARNING on andi-shyti/i2c/i2c-host sre-power-supply/for-next linus/master v6.11 next-20240927]
[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/Chris-Packham/dt-bindings-reset-syscon-reboot-Add-reg-property/20240926-060355
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20240925215847.3594898-7-chris.packham%40alliedtelesis.co.nz
patch subject: [PATCH v5 6/6] i2c: Add driver for the RTL9300 I2C controller
config: csky-randconfig-r111-20240929 (https://download.01.org/0day-ci/archive/20240929/202409291025.P4M4O1F2-lkp@intel.com/config)
compiler: csky-linux-gcc (GCC) 14.1.0
reproduce: (https://download.01.org/0day-ci/archive/20240929/202409291025.P4M4O1F2-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/202409291025.P4M4O1F2-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/i2c/busses/i2c-rtl9300.c:321:27: sparse: sparse: symbol 'rtl9300_i2c_quirks' was not declared. Should it be static?

vim +/rtl9300_i2c_quirks +321 drivers/i2c/busses/i2c-rtl9300.c

   320	
 > 321	struct i2c_adapter_quirks rtl9300_i2c_quirks = {
   322		.flags		= I2C_AQ_NO_CLK_STRETCH,
   323		.max_read_len	= 16,
   324		.max_write_len	= 16,
   325	};
   326	

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

Hi Andi,

This is a fixup for the spare complaint from the kernel test robot
https://lore.kernel.org/lkml/202409291025.P4M4O1F2-lkp@intel.com/#t

Not sure if you want to fold this into what is already in
andi-shyti/i2c/i2c-host or if you want me to send it as a new patch.
---
 drivers/i2c/busses/i2c-rtl9300.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
index ed9a45a9d803..f0bb0ede79ce 100644
--- a/drivers/i2c/busses/i2c-rtl9300.c
+++ b/drivers/i2c/busses/i2c-rtl9300.c
@@ -318,7 +318,7 @@ static const struct i2c_algorithm rtl9300_i2c_algo = {
 	.functionality	= rtl9300_i2c_func,
 };
 
-struct i2c_adapter_quirks rtl9300_i2c_quirks = {
+static struct i2c_adapter_quirks rtl9300_i2c_quirks = {
 	.flags		= I2C_AQ_NO_CLK_STRETCH,
 	.max_read_len	= 16,
 	.max_write_len	= 16,
-- 
2.46.2

Hi Chris,

On Mon, Sep 30, 2024 at 09:09:34AM GMT, Chris Packham wrote:
> Hi Andi,
> 
> This is a fixup for the spare complaint from the kernel test robot
> https://lore.kernel.org/lkml/202409291025.P4M4O1F2-lkp@intel.com/#t
> 
> Not sure if you want to fold this into what is already in
> andi-shyti/i2c/i2c-host or if you want me to send it as a new patch.

no worries, I can take care of it.

Andi

> ---
>  drivers/i2c/busses/i2c-rtl9300.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
> index ed9a45a9d803..f0bb0ede79ce 100644
> --- a/drivers/i2c/busses/i2c-rtl9300.c
> +++ b/drivers/i2c/busses/i2c-rtl9300.c
> @@ -318,7 +318,7 @@ static const struct i2c_algorithm rtl9300_i2c_algo = {
>  	.functionality	= rtl9300_i2c_func,
>  };
>  
> -struct i2c_adapter_quirks rtl9300_i2c_quirks = {
> +static struct i2c_adapter_quirks rtl9300_i2c_quirks = {
>  	.flags		= I2C_AQ_NO_CLK_STRETCH,
>  	.max_read_len	= 16,
>  	.max_write_len	= 16,
> -- 
> 2.46.2
>

Hi Andi,

On 2/10/24 23:57, Andi Shyti wrote:
> Hi Chris,
>
> On Mon, Sep 30, 2024 at 09:09:34AM GMT, Chris Packham wrote:
>> Hi Andi,
>>
>> This is a fixup for the spare complaint from the kernel test robot
>> https://scanmail.trustwave.com/?c=20988&d=8Kn95gKUGD1_OL8d257ypj3kPxHsjXG_y2-BvWXRiQ&u=https%3a%2f%2flore%2ekernel%2eorg%2flkml%2f202409291025%2eP4M4O1F2-lkp%40intel%2ecom%2f%23t
>>
>> Not sure if you want to fold this into what is already in
>> andi-shyti/i2c/i2c-host or if you want me to send it as a new patch.
> no worries, I can take care of it.
>
> Andi

Just chasing up this series.  Did it land anywhere? Were you waiting for 
me to send a v6?

I think I've clarified the SoC naming with Krzysztof so he might like me 
to send a v6 dropping the wildcard rtl9300. But I didn't want to send a 
v6 if v5 was already sitting in a tree somewhere else.

>> ---
>>   drivers/i2c/busses/i2c-rtl9300.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
>> index ed9a45a9d803..f0bb0ede79ce 100644
>> --- a/drivers/i2c/busses/i2c-rtl9300.c
>> +++ b/drivers/i2c/busses/i2c-rtl9300.c
>> @@ -318,7 +318,7 @@ static const struct i2c_algorithm rtl9300_i2c_algo = {
>>   	.functionality	= rtl9300_i2c_func,
>>   };
>>   
>> -struct i2c_adapter_quirks rtl9300_i2c_quirks = {
>> +static struct i2c_adapter_quirks rtl9300_i2c_quirks = {
>>   	.flags		= I2C_AQ_NO_CLK_STRETCH,
>>   	.max_read_len	= 16,
>>   	.max_write_len	= 16,
>> -- 
>> 2.46.2
>>