peci: Add peci-cpu driver

PECI is an interface that may be used by different types of devices.
Add a peci-cpu driver compatible with Intel processors. The driver is
responsible for handling auxiliary devices that can subsequently be used
by other drivers (e.g. hwmons).

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Link: https://lore.kernel.org/r/20220208153639.255278-10-iwona.winiarska@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

peci: Add support for PECI device drivers

Add support for PECI device drivers, which unlike PECI controller
drivers are actually able to provide functionalities to userspace.

Also, extend peci_request API to allow querying more details about PECI
device (e.g. model/family), that's going to be used to find a compatible
peci_driver.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Link: https://lore.kernel.org/r/20220208153639.255278-9-iwona.winiarska@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

peci: Add sysfs interface for PECI bus

PECI devices may not be discoverable at the time when PECI controller is
being added (e.g. BMC can boot up when the Host system is still in S5).
Since we currently don't have the capabilities to figure out the Host
system state inside the PECI subsystem itself, we have to rely on
userspace to do it for us.

In the future, PECI subsystem may be expanded with mechanisms that allow
us to avoid depending on userspace interaction (e.g. CPU presence could
be detected using GPIO, and the information on whether it's discoverable
could be obtained over IPMI).
Unfortunately, those methods may ultimately not be available (support
will vary from platform to platform), which means that we still need
platform independent method triggered by userspace.

Acked-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Link: https://lore.kernel.org/r/20220208153639.255278-8-iwona.winiarska@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

peci: Add device detection

Since PECI devices are discoverable, we can dynamically detect devices
that are actually available in the system.

This change complements the earlier implementation by rescanning PECI
bus to detect available devices. For this purpose, it also introduces the
minimal API for PECI requests.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Link: https://lore.kernel.org/r/20220208153639.255278-7-iwona.winiarska@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>