[PATCH v8 1/9] i2c: rtl9300: use regmap fields and API for registers

Jonas Jelonek
2025-09-27T10:19:54Z

Adapt the RTL9300 I2C controller driver to use more of the regmap
API, especially make use of reg_field and regmap_field instead of macros
to represent registers. Most register operations are performed through
regmap_field_* API then.

Handle SCL selection using separate chip-specific functions since this
is already known to differ between the Realtek SoC families in such a
way that this cannot be properly handled using just a different
reg_field.

This makes it easier to add support for newer generations or to handle
differences between specific revisions within a series. Just by
defining a separate driver data structure with the corresponding
register field definitions and linking it to a new compatible.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Tested-by: Sven Eckelmann <sven@narfation.org>
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz> # On RTL9302C based board
Tested-by: Markus Stockhausen <markus.stockhausen@gmx.de>
---
drivers/i2c/busses/i2c-rtl9300.c | 192 ++++++++++++++++++++-----------
1 file changed, 124 insertions(+), 68 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
index 9e6232075137..8483bab72146 100644
--- a/drivers/i2c/busses/i2c-rtl9300.c
+++ b/drivers/i2c/busses/i2c-rtl9300.c
@@ -23,97 +23,117 @@ struct rtl9300_i2c_chan {
u8 sda_pin;
};

+enum rtl9300_i2c_reg_scope {
+ REG_SCOPE_GLOBAL,
+ REG_SCOPE_MASTER,
+};
+
+struct rtl9300_i2c_reg_field {
+ struct reg_field field;
+ enum rtl9300_i2c_reg_scope scope;
+};
+
+enum rtl9300_i2c_reg_fields {
+ F_DATA_WIDTH = 0,
+ F_DEV_ADDR,
+ F_I2C_FAIL,
+ F_I2C_TRIG,
+ F_MEM_ADDR,
+ F_MEM_ADDR_WIDTH,
+ F_RD_MODE,
+ F_RWOP,
+ F_SCL_FREQ,
+ F_SCL_SEL,
+ F_SDA_OUT_SEL,
+ F_SDA_SEL,
+
+ /* keep last */
+ F_NUM_FIELDS
+};
+
+struct rtl9300_i2c_drv_data {
+ struct rtl9300_i2c_reg_field field_desc[F_NUM_FIELDS];
+ int (*select_scl)(struct rtl9300_i2c *i2c, u8 scl);
+ u32 data_reg;
+ u8 max_nchan;
+};
+
#define RTL9300_I2C_MUX_NCHAN 8

struct rtl9300_i2c {
struct regmap *regmap;
struct device *dev;
struct rtl9300_i2c_chan chans[RTL9300_I2C_MUX_NCHAN];
+ struct regmap_field *fields[F_NUM_FIELDS];
u32 reg_base;
+ u32 data_reg;
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);
+ ret = regmap_field_write(i2c->fields[F_MEM_ADDR_WIDTH], len);
if (ret)
return ret;

- val = reg << RTL9300_I2C_MST_CTRL1_MEM_ADDR_OFS;
- mask = RTL9300_I2C_MST_CTRL1_MEM_ADDR_MASK;
+ return regmap_field_write(i2c->fields[F_MEM_ADDR], reg);
+}

- return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+static int rtl9300_i2c_select_scl(struct rtl9300_i2c *i2c, u8 scl)
+{
+ return regmap_field_write(i2c->fields[F_SCL_SEL], 1);
}

static int rtl9300_i2c_config_io(struct rtl9300_i2c *i2c, u8 sda_pin)
{
+ struct rtl9300_i2c_drv_data *drv_data;
int ret;
- u32 val, mask;

- ret = regmap_update_bits(i2c->regmap, RTL9300_I2C_MST_GLB_CTRL, BIT(sda_pin), BIT(sda_pin));
+ drv_data = (struct rtl9300_i2c_drv_data *)device_get_match_data(i2c->dev);
+
+ ret = regmap_field_update_bits(i2c->fields[F_SDA_SEL], 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;
+ ret = regmap_field_write(i2c->fields[F_SDA_OUT_SEL], sda_pin);
+ if (ret)
+ return ret;

- return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+ return drv_data->select_scl(i2c, 0);
}

static int rtl9300_i2c_config_xfer(struct rtl9300_i2c *i2c, struct rtl9300_i2c_chan *chan,
u16 addr, u16 len)
{
- u32 val, mask;
+ int ret;

if (len < 1 || len > 16)
return -EINVAL;

- 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;
+ ret = regmap_field_write(i2c->fields[F_SCL_FREQ], chan->bus_freq);
+ if (ret)
+ return ret;

- val |= ((len - 1) & 0xf) << RTL9300_I2C_MST_CTRL2_DATA_WIDTH_OFS;
- mask |= RTL9300_I2C_MST_CTRL2_DATA_WIDTH_MASK;
+ ret = regmap_field_write(i2c->fields[F_DEV_ADDR], addr);
+ if (ret)
+ return ret;

- mask |= RTL9300_I2C_MST_CTRL2_RD_MODE;
+ ret = regmap_field_write(i2c->fields[F_DATA_WIDTH], (len - 1) & 0xf);
+ if (ret)
+ return ret;

- return regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL2, mask, val);
+ return regmap_field_write(i2c->fields[F_RD_MODE], 0);
}

static int rtl9300_i2c_read(struct rtl9300_i2c *i2c, u8 *buf, int len)
@@ -124,8 +144,7 @@ static int rtl9300_i2c_read(struct rtl9300_i2c *i2c, u8 *buf, int len)
if (len > 16)
return -EIO;

- ret = regmap_bulk_read(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0,
- vals, ARRAY_SIZE(vals));
+ ret = regmap_bulk_read(i2c->regmap, i2c->data_reg, vals, ARRAY_SIZE(vals));
if (ret)
return ret;

@@ -152,52 +171,49 @@ static int rtl9300_i2c_write(struct rtl9300_i2c *i2c, u8 *buf, int len)
vals[reg] |= buf[i] << shift;
}

- return regmap_bulk_write(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0,
- vals, ARRAY_SIZE(vals));
+ return regmap_bulk_write(i2c->regmap, i2c->data_reg, 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);
+ return regmap_write(i2c->regmap, i2c->data_reg, 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;
+ u32 val;
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_field_write(i2c->fields[F_RWOP], read_write == I2C_SMBUS_WRITE);
+ if (ret)
+ return ret;

- ret = regmap_update_bits(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, mask, val);
+ ret = regmap_field_write(i2c->fields[F_I2C_TRIG], 1);
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, 100000);
+ ret = regmap_field_read_poll_timeout(i2c->fields[F_I2C_TRIG], val, !val, 100, 100000);
if (ret)
return ret;

- if (val & RTL9300_I2C_MST_CTRL1_I2C_FAIL)
+ ret = regmap_field_read(i2c->fields[F_I2C_FAIL], &val);
+ if (ret)
+ return ret;
+ if (val)
return -EIO;

if (read_write == I2C_SMBUS_READ) {
switch (size) {
case I2C_SMBUS_BYTE:
case I2C_SMBUS_BYTE_DATA:
- ret = regmap_read(i2c->regmap,
- i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0, &val);
+ ret = regmap_read(i2c->regmap, i2c->data_reg, &val);
if (ret)
return ret;
data->byte = val & 0xff;
break;
case I2C_SMBUS_WORD_DATA:
- ret = regmap_read(i2c->regmap,
- i2c->reg_base + RTL9300_I2C_MST_DATA_WORD0, &val);
+ ret = regmap_read(i2c->regmap, i2c->data_reg, &val);
if (ret)
return ret;
data->word = val & 0xffff;
@@ -355,9 +371,11 @@ static int rtl9300_i2c_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct rtl9300_i2c *i2c;
+ struct fwnode_handle *child;
+ struct rtl9300_i2c_drv_data *drv_data;
+ struct reg_field fields[F_NUM_FIELDS];
u32 clock_freq, sda_pin;
int ret, i = 0;
- struct fwnode_handle *child;

i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
if (!i2c)
@@ -376,9 +394,22 @@ static int rtl9300_i2c_probe(struct platform_device *pdev)

platform_set_drvdata(pdev, i2c);

- if (device_get_child_node_count(dev) > RTL9300_I2C_MUX_NCHAN)
+ drv_data = (struct rtl9300_i2c_drv_data *)device_get_match_data(i2c->dev);
+ if (device_get_child_node_count(dev) > drv_data->max_nchan)
return dev_err_probe(dev, -EINVAL, "Too many channels\n");

+ i2c->data_reg = i2c->reg_base + drv_data->data_reg;
+ for (i = 0; i < F_NUM_FIELDS; i++) {
+ fields[i] = drv_data->field_desc[i].field;
+ if (drv_data->field_desc[i].scope == REG_SCOPE_MASTER)
+ fields[i].reg += i2c->reg_base;
+ }
+ ret = devm_regmap_field_bulk_alloc(dev, i2c->regmap, i2c->fields,
+ fields, F_NUM_FIELDS);
+ if (ret)
+ return ret;
+
+ i = 0;
device_for_each_child_node(dev, child) {
struct rtl9300_i2c_chan *chan = &i2c->chans[i];
struct i2c_adapter *adap = &chan->adap;
@@ -395,7 +426,6 @@ static int rtl9300_i2c_probe(struct platform_device *pdev)
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;
@@ -427,11 +457,37 @@ static int rtl9300_i2c_probe(struct platform_device *pdev)
return 0;
}

+#define GLB_REG_FIELD(reg, msb, lsb) \
+ { .field = REG_FIELD(reg, msb, lsb), .scope = REG_SCOPE_GLOBAL }
+#define MST_REG_FIELD(reg, msb, lsb) \
+ { .field = REG_FIELD(reg, msb, lsb), .scope = REG_SCOPE_MASTER }
+
+static const struct rtl9300_i2c_drv_data rtl9300_i2c_drv_data = {
+ .field_desc = {
+ [F_MEM_ADDR] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 8, 31),
+ [F_SDA_OUT_SEL] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 4, 6),
+ [F_SCL_SEL] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 3, 3),
+ [F_RWOP] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 2, 2),
+ [F_I2C_FAIL] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 1, 1),
+ [F_I2C_TRIG] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 0, 0),
+ [F_RD_MODE] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 15, 15),
+ [F_DEV_ADDR] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 8, 14),
+ [F_DATA_WIDTH] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 4, 7),
+ [F_MEM_ADDR_WIDTH] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 2, 3),
+ [F_SCL_FREQ] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 0, 1),
+ [F_SDA_SEL] = GLB_REG_FIELD(RTL9300_I2C_MST_GLB_CTRL, 0, 7),
+ },
+ .select_scl = rtl9300_i2c_select_scl,
+ .data_reg = RTL9300_I2C_MST_DATA_WORD0,
+ .max_nchan = RTL9300_I2C_MUX_NCHAN,
+};
+
+
static const struct of_device_id i2c_rtl9300_dt_ids[] = {
- { .compatible = "realtek,rtl9301-i2c" },
- { .compatible = "realtek,rtl9302b-i2c" },
- { .compatible = "realtek,rtl9302c-i2c" },
- { .compatible = "realtek,rtl9303-i2c" },
+ { .compatible = "realtek,rtl9301-i2c", .data = (void *) &rtl9300_i2c_drv_data },
+ { .compatible = "realtek,rtl9302b-i2c", .data = (void *) &rtl9300_i2c_drv_data },
+ { .compatible = "realtek,rtl9302c-i2c", .data = (void *) &rtl9300_i2c_drv_data },
+ { .compatible = "realtek,rtl9303-i2c", .data = (void *) &rtl9300_i2c_drv_data },
{}
};
MODULE_DEVICE_TABLE(of, i2c_rtl9300_dt_ids);
--
2.48.1