diff options
Diffstat (limited to 'Documentation/hwmon/pmbus-core.rst')
| -rw-r--r-- | Documentation/hwmon/pmbus-core.rst | 112 |
1 files changed, 99 insertions, 13 deletions
diff --git a/Documentation/hwmon/pmbus-core.rst b/Documentation/hwmon/pmbus-core.rst index 501b37b0610d..fdfb23773148 100644 --- a/Documentation/hwmon/pmbus-core.rst +++ b/Documentation/hwmon/pmbus-core.rst @@ -121,6 +121,15 @@ Specifically, it provides the following information. non-standard PMBus commands to standard commands, or to augment standard command return values with device specific information. +PEC Support +=========== + +Many PMBus devices support SMBus PEC (Packet Error Checking). If supported +by both the I2C adapter and by the PMBus chip, it is by default enabled. +If PEC is supported, the PMBus core driver adds an attribute named 'pec' to +the I2C device. This attribute can be used to control PEC support in the +communication with the PMBus chip. + API functions ============= @@ -165,7 +174,7 @@ Read byte from page <page>, register <reg>. int (*read_word_data)(struct i2c_client *client, int page, int phase, int reg); -Read word from page <page>, phase <pase>, register <reg>. If the chip does not +Read word from page <page>, phase <phase>, register <reg>. If the chip does not support multiple phases, the phase parameter can be ignored. If the chip supports multiple phases, a phase value of 0xff indicates all phases. @@ -270,8 +279,7 @@ obtain the chip status. Therefore, it must _not_ be called from that function. :: - int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id, - struct pmbus_driver_info *info); + int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info); Execute probe function. Similar to standard probe function for other drivers, with the pointer to struct pmbus_driver_info as additional argument. Calls @@ -280,12 +288,6 @@ function. :: - void pmbus_do_remove(struct i2c_client *client); - -Execute driver remove function. Similar to standard driver remove function. - -:: - const struct pmbus_driver_info *pmbus_get_driver_info(struct i2c_client *client); @@ -296,12 +298,30 @@ PMBus driver platform data ========================== PMBus platform data is defined in include/linux/pmbus.h. Platform data -currently only provides a flag field with a single bit used:: +currently provides a flags field with four bits used:: + + #define PMBUS_SKIP_STATUS_CHECK BIT(0) + + #define PMBUS_WRITE_PROTECTED BIT(1) + + #define PMBUS_NO_CAPABILITY BIT(2) - #define PMBUS_SKIP_STATUS_CHECK (1 << 0) + #define PMBUS_READ_STATUS_AFTER_FAILED_CHECK BIT(3) + + #define PMBUS_NO_WRITE_PROTECT BIT(4) + + #define PMBUS_USE_COEFFICIENTS_CMD BIT(5) + + #define PMBUS_OP_PROTECTED BIT(6) + + #define PMBUS_VOUT_PROTECTED BIT(7) struct pmbus_platform_data { u32 flags; /* Device specific flags */ + + /* regulator support */ + int num_regulators; + struct regulator_init_data *reg_init_data; }; @@ -309,8 +329,9 @@ Flags ----- PMBUS_SKIP_STATUS_CHECK - During register detection, skip checking the status register for - communication or command errors. + +During register detection, skip checking the status register for +communication or command errors. Some PMBus chips respond with valid data when trying to read an unsupported register. For such chips, checking the status register is mandatory when @@ -322,3 +343,68 @@ status register must be disabled. Some i2c controllers do not support single-byte commands (write commands with no data, i2c_smbus_write_byte()). With such controllers, clearing the status register is impossible, and the PMBUS_SKIP_STATUS_CHECK flag must be set. + +PMBUS_WRITE_PROTECTED + +Set if the chip is write protected and write protection is not determined +by the standard WRITE_PROTECT command. + +PMBUS_NO_CAPABILITY + +Some PMBus chips don't respond with valid data when reading the CAPABILITY +register. For such chips, this flag should be set so that the PMBus core +driver doesn't use CAPABILITY to determine its behavior. + +PMBUS_READ_STATUS_AFTER_FAILED_CHECK + +Read the STATUS register after each failed register check. + +Some PMBus chips end up in an undefined state when trying to read an +unsupported register. For such chips, it is necessary to reset the +chip pmbus controller to a known state after a failed register check. +This can be done by reading a known register. By setting this flag the +driver will try to read the STATUS register after each failed +register check. This read may fail, but it will put the chip into a +known state. + +PMBUS_NO_WRITE_PROTECT + +Some PMBus chips respond with invalid data when reading the WRITE_PROTECT +register. For such chips, this flag should be set so that the PMBus core +driver doesn't use the WRITE_PROTECT command to determine its behavior. + +PMBUS_USE_COEFFICIENTS_CMD + +When this flag is set the PMBus core driver will use the COEFFICIENTS +register to initialize the coefficients for the direct mode format. + +PMBUS_OP_PROTECTED + +Set if the chip OPERATION command is protected and protection is not +determined by the standard WRITE_PROTECT command. + +PMBUS_VOUT_PROTECTED + +Set if the chip VOUT_COMMAND command is protected and protection is not +determined by the standard WRITE_PROTECT command. + +Module parameter +---------------- + +pmbus_core.wp: PMBus write protect forced mode + +PMBus may come up with a variety of write protection configuration. +'pmbus_core.wp' may be used if a particular write protection is necessary. +The ability to actually alter the protection may also depend on the chip +so the actual runtime write protection configuration may differ from +the requested one. pmbus_core currently support the following value: + +* 0: write protection removed. +* 1: Disable all writes except to the WRITE_PROTECT, OPERATION, + PAGE, ON_OFF_CONFIG and VOUT_COMMAND commands. +* 2: Disable all writes except to the WRITE_PROTECT, OPERATION and + PAGE commands. +* 3: Disable all writes except to the WRITE_PROTECT command. Note that + protection should include the PAGE register. This may be problematic + for multi-page chips, if the chips strictly follows the PMBus + specification, preventing the chip from changing the active page. |