diff options
| -rw-r--r-- | drivers/hwmon/spd5118.c | 75 |
1 files changed, 64 insertions, 11 deletions
diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c index 92a3cb0bb515..5da44571b6a0 100644 --- a/drivers/hwmon/spd5118.c +++ b/drivers/hwmon/spd5118.c @@ -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[] = { |