hwmon: (occ/p9_sbe) Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new() which already returns void. Eventually after all drivers
are converted, .remove_new() is renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230918085951.1234172-12-u.kleine-koenig@pengutronix.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (occ) Check for device property for setting OCC active during probe

A previous commit changed the existing behavior of the driver to skip
attempting to communicate with the OCC during probe. Return to the
previous default behavior of automatically communicating with the OCC
and make it optional with a new device-tree property.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220809200701.218059-4-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

hwmon (occ): Retry for checksum failure

Due to the OCC communication design with a shared SRAM area,
checkum errors are expected due to corrupted buffer from OCC
communications with other system components. Therefore, retry
the command twice in the event of a checksum failure.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220426154956.27205-3-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

hwmon: (occ) Delete unnecessary NULL check

kvfree(NULL) is safe. NULL check before kvfree() is not needed.
Delete them to simplify the code.

Generated by coccinelle script:
scripts/coccinelle/free/ifnullfree.cocci

Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220606131401.4053036-1-william.xuanziyang@huawei.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

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>

mm: move kvmalloc-related functions to slab.h

Not all files in the kernel should include mm.h. Migrating callers from
kmalloc to kvmalloc is easier if the kvmalloc functions are in slab.h.

[akpm@linux-foundation.org: move the new kvrealloc() also]
[akpm@linux-foundation.org: drivers/hwmon/occ/p9_sbe.c needs slab.h]

Link: https://lkml.kernel.org/r/20210622215757.3525604-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

hwmon: (occ) Provide the SBEFIFO FFDC in binary sysfs

Save any FFDC provided by the OCC driver, and provide it to userspace
through a binary sysfs entry. Notify userspace pollers when there is an
error too.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211019205307.36946-5-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

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 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 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): Add command transport method for P8 and P9

For the P8 OCC, add the procedure to send a command to the OCC over I2C
bus. This involves writing the OCC command registers with serial
communication operations (SCOMs) interpreted by the I2C slave. For the
P9 OCC, add a procedure to use the OCC in-kernel API to send a command
to the OCC through the SBE.

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>