Basic OPAL sensor support for POWER9 platforms

[jhibbits]

Summary

PowerNV architectures (in the test case POWER9) export sensors via the device
tree, which are accessed via OPAL calls. This adds sysctl nodes for each
device in a generic fashion. New sysctl nodes are:

dev.opal_sensor.N.sensor
dev.opal_sensor.N.sensor_min
dev.opal_sensor.N.sensor_max
dev.opal_sensor.N.type
dev.opal_sensor.N.label

These are rooted at a parent attachment under opal, called opalsens. This does
not add support for the "sensor grooups" defined in the device tree.

[jhibbits]

Just a note, the OPAL calls additions to opal.h are separate, and simply \#define additions. I'm sure there must be a better name than opal_sensor, so soliciting opinions on that.

[breno.leitao_gmail.com]

Hi Justin.

It seems that this diff does not contain the changes in opal.h, as the definition for OPAL_SENSOR_READ and others.

[breno.leitao_gmail.com]

sys/powerpc/powernv/opal_sensor.c

102

What if OPAL_SUCCESS is returned? it seems that val32 will be empty later.

107

We probably want to check for OPAL_BUSY_EVENT and quite the loop after a while, mainly if OPAL_BUSY is returned forever.

116

val32 will be empty if we get OPAL_SUCCESS on the first call

[jhibbits]

In D15362#323855, @breno.leitao_gmail.com wrote:

Hi Justin.

It seems that this diff does not contain the changes in opal.h, as the definition for OPAL_SENSOR_READ and others.

I mentioned above that those definitions aren't included here because I've already made other changes to opal.h so extracting them for the diff seemed silly for first glance. They are:

#define OPAL_SENSOR_READ 88
#define OPAL_SENSOR_GROUP_CLEAR 156
#define OPAL_SENSOR_READ_U64 162
#define OPAL_SENSOR_GROUP_ENABLE 163

sys/powerpc/powernv/opal_sensor.c

102

If OPAL_SUCCESS is returned val32 will have been populated by the OPAL_SENSOR_READ call.

116

Se above, it gets populated immediately by the call.

[jhibbits]

Add a small delay, and a timeout, if a sensor needs extra time
(OPAL_ASYNC_COMPLETION/OPAL_BUSY).

[jhibbits]

sys/powerpc/powernv/opal_sensor.c

109

Oops, typo. Should be OPAL_CHECK_ASYNC_COMPLETION.

[breno.leitao_gmail.com]

I reviewed this code and it seems OK to be integrated.