hwmon: (occ) Prevent power cap command overwriting poll response

Currently, the response to the power cap command overwrites the
first eight bytes of the poll response, since the commands use
the same buffer. This means that user's get the wrong data between
the time of sending the power cap and the next poll response update.
Fix this by specifying a different buffer for the power cap command
response.

Fixes: 5b5513b88002 ("hwmon: Add On-Chip Controller (OCC) hwmon driver")
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220628203029.51747-1-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Delay hwmon registration until user request

Instead of registering the hwmon device at probe time, use the
existing "occ_active" sysfs file to control when the driver polls
the OCC for sensor data and registers with hwmon. The reason for
this change is that the SBE, which is the device by which the
driver communicates with the OCC, cannot handle communications
during certain system state transitions, resulting in
unrecoverable system errors.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220427140443.11428-1-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Add sysfs entry for OCC mode

BMC control applications need to check the OCC mode returned by the
OCC poll response, so export it in sysfs with the other OCC-specific
data.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20220215151022.7498-3-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Add sysfs entry for IPS (Idle Power Saver) status

BMC control applications need to check the Idle Power Saver status
byte returned by the OCC poll response, so export it in sysfs with
the other OCC-specific data.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20220215151022.7498-2-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Remove sequence numbering and checksum calculation

Checksumming of the request and sequence numbering is now done in the
OCC interface driver in order to keep unique sequence numbers. So
remove those in the hwmon driver. Also, add the command length to the
send_cmd function pointer, since the checksum must be placed in the
last two bytes of the command. The submit interface must receive the
exact size of the command - previously it could be rounded to the
nearest 8 bytes with no consequence.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210721190231.117185-3-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

hwmon: (occ) Fix poll rate limiting

The poll rate limiter time was initialized at zero. This breaks the
comparison in time_after if jiffies is large. Switch to storing the
next update time rather than the previous time, and initialize the
time when the device is probed.

Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20210429151336.18980-1-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

OCC: FSI and hwmon: Add sequence numbering

Sequence numbering of the commands submitted to the OCC is required by
the OCC interface specification. Add sequence numbering and check for
the correct sequence number on the response.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Lei YU <mine260309@gmail.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>

hwmon: (occ) Store error condition for rate-limited polls

The OCC driver limits the rate of sending poll commands to the OCC. If a
user reads a hwmon entry after a poll response resulted in an error and
is rate-limited, the error is invisible to the user. Fix this by storing
the last error and returning that in the rate-limited case.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Fix license headers

Files have inconsistent license information.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon (occ): Add sysfs attributes for additional OCC data

The OCC provides a variety of additional information about the state of
the host processor, such as throttling, error conditions, and the number
of OCCs detected in the system. This information is essential to service
processor applications such as fan control and host management.
Therefore, export this data in the form of sysfs attributes attached to
the platform device (to which the hwmon device is also attached).

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon (occ): Add sensor attributes and register hwmon device

Setup the sensor attributes for every OCC sensor found by the first poll
response. Register the attributes with hwmon.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon (occ): Add sensor types and versions

Add structures to define all sensor types and versions. Add sysfs show
and store functions for each sensor type. Add a method to construct the
"set user power cap" command and send it to the OCC. Add rate limit to
polling the OCC (in case user-space reads our hwmon entries rapidly).

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon (occ): Parse OCC poll response

Add method to parse the response from the OCC poll command. This only
needs to be done during probe(), since the OCC shouldn't change the
number or format of sensors while it's running. The parsed response
allows quick access to sensor data, as well as information on the
number and version of sensors, which we need to instantiate hwmon
attributes.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: Add On-Chip Controller (OCC) hwmon driver

The OCC is a device embedded on a POWER processor that collects and
aggregates sensor data from the processor and system. The OCC can
provide the raw sensor data as well as perform thermal and power
management on the system.

This driver provides a hwmon interface to the OCC from a service
processor (e.g. a BMC). The driver supports both POWER8 and POWER9 OCCs.
Communications with the POWER8 OCC are established over standard I2C
bus. The driver communicates with the POWER9 OCC through the FSI-based
OCC driver, which handles the lower-level communication details.

This patch lays out the structure of the OCC hwmon driver. There are two
platform drivers, one each for P8 and P9 OCCs. These are probed through
the I2C tree and the FSI-based OCC driver, respectively. The patch also
defines the first common structures and methods between the two OCC
versions.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
[groeck: Fix up SPDX license identifier]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>