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hwmon: (spd5118) Detect and support 16-bit register addressing

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Add support for SPD5118 compatible chips with 16-bit addressing enabled
which are connected to I2C controllers.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Guenter Roeck 2024-06-19 09:40:36 -07:00
parent be82d39c53
commit a852162efb
1 changed files with 64 additions and 11 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

75
drivers/hwmon/spd5118.c
View file

@ -461,7 +461,7 @@ static const struct regmap_range_cfg spd5118_i2c_regmap_range_cfg[] = {
},
};
static const struct regmap_config spd5118_i2c_regmap_config = {
static const struct regmap_config spd5118_regmap8_config = {
.reg_bits = 8,
.val_bits = 8,
.max_register = 0x7ff,
@ -473,6 +473,15 @@ static const struct regmap_config spd5118_i2c_regmap_config = {
.num_ranges = ARRAY_SIZE(spd5118_i2c_regmap_range_cfg),
};
static const struct regmap_config spd5118_regmap16_config = {
.reg_bits = 16,
.val_bits = 8,
.max_register = 0x7ff,
.writeable_reg = spd5118_writeable_reg,
.volatile_reg = spd5118_volatile_reg,
.cache_type = REGCACHE_MAPLE,
};
static int spd5118_suspend(struct device *dev)
{
struct spd5118_data *data = dev_get_drvdata(dev);
@ -510,7 +519,8 @@ static int spd5118_resume(struct device *dev)
static DEFINE_SIMPLE_DEV_PM_OPS(spd5118_pm_ops, spd5118_suspend, spd5118_resume);
static int spd5118_common_probe(struct device *dev, struct regmap *regmap)
static int spd5118_common_probe(struct device *dev, struct regmap *regmap,
bool is_16bit)
{
unsigned int capability, revision, vendor, bank;
struct spd5118_data *data;
@ -527,12 +537,7 @@ static int spd5118_common_probe(struct device *dev, struct regmap *regmap)
if (!(capability & SPD5118_CAP_TS_SUPPORT))
return -ENODEV;
/*
* 16-bit register addresses are not (yet) supported with I2C.
* Therefore, if this is an I2C device, register addresses must be
* 8 bit wide.
*/
data->is_16bit = !!i2c_verify_adapter(dev);
data->is_16bit = is_16bit;
err = regmap_read(regmap, SPD5118_REG_REVISION, &revision);
if (err)
@ -675,21 +680,69 @@ static int spd5118_i2c_init(struct i2c_client *client)
return 0;
}
/*
* 16-bit addressing note:
*
* If I2C_FUNC_I2C is not supported by an I2C adapter driver, regmap uses
* SMBus operations as alternative. To simulate a read operation with a 16-bit
* address, it writes the address using i2c_smbus_write_byte_data(), followed
* by one or more calls to i2c_smbus_read_byte() to read the data.
* Per spd5118 standard, a read operation after writing the address must start
* with <Sr> (Repeat Start). However, a SMBus read byte operation starts with
* <S> (Start). This resets the register address in the spd5118 chip. As result,
* i2c_smbus_read_byte() always returns data from register address 0x00.
*
* A working alternative to access chips with 16-bit register addresses in the
* absence of I2C_FUNC_I2C support is not known.
*
* For this reason, 16-bit addressing can only be supported with I2C if the
* adapter supports I2C_FUNC_I2C.
*
* For I2C, the addressing mode selected by the BIOS must not be changed.
* Experiments show that at least some PC BIOS versions will not change the
* addressing mode on a soft reboot and end up in setup, claiming that some
* configuration change happened. This will happen again after a power cycle,
* which does reset the addressing mode. To prevent this from happening,
* detect if 16-bit addressing is enabled and always use the currently
* configured addressing mode.
*/
static int spd5118_i2c_probe(struct i2c_client *client)
{
const struct regmap_config *config;
struct device *dev = &client->dev;
struct regmap *regmap;
int err;
int err, mode;
bool is_16bit;
err = spd5118_i2c_init(client);
if (err)
return err;
regmap = devm_regmap_init_i2c(client, &spd5118_i2c_regmap_config);
mode = i2c_smbus_read_byte_data(client, SPD5118_REG_I2C_LEGACY_MODE);
if (mode < 0)
return mode;
is_16bit = mode & SPD5118_LEGACY_MODE_ADDR;
if (is_16bit) {
/*
* See 16-bit addressing note above explaining why it is
* necessary to check for I2C_FUNC_I2C support here.
*/
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
dev_err(dev, "Adapter does not support 16-bit register addresses\n");
return -ENODEV;
}
config = &spd5118_regmap16_config;
} else {
config = &spd5118_regmap8_config;
}
regmap = devm_regmap_init_i2c(client, config);
if (IS_ERR(regmap))
return dev_err_probe(dev, PTR_ERR(regmap), "regmap init failed\n");
return spd5118_common_probe(dev, regmap);
return spd5118_common_probe(dev, regmap, is_16bit);
}
static const struct i2c_device_id spd5118_i2c_id[] = {