pta: stats: add commands to print clock and regulator trees

[etienne-lms]

Add statistics PTA commands STATS_CMD_PRINT_DRIVERS_INFO to print device drivers information on console. The implementation currently allows to print the clock tree and the regulator tree to core console.

This is a follow-up of changes discussed in #6481.

I have picked commit "drivers: regulator: fix variable sized voltages fallback" from P-R #6487 latest state to ensure pta_stats.c successfully builds with clang (inclusion of regulator.h). I'll remove this commit and rebase this P-R on top of #6487 once its merged.

[etienne-lms]

@jforissier, in #6481 (comment) you asked from the PTA command name to be singular (s/STATS_CMD_PRINT_DRIVERS_INFO/STATS_CMD_PRINT_DRIVER_INFO/). I've restored the plural form as printing clock or regulator trees relate to several drivers rather than not a single one. Thinking twice, in the end, maybe singular is more appropriate...

[jforissier]

@etienne-lms AFAICT singular tends to be more common when a noun is used as an adjective. I believe "driver info" is OK to mean "information about one or more driver(s)".

[etienne-lms]

Ok, I'll update.

[jforissier]

For " pta: stats: add commands to print clock and regulator trees" with fixup:

Reviewed-by: Jerome Forissier <[email protected]>

Do you have the xtest side of things?

[etienne-lms]

Do you have the xtest side of things?

Yes, I was waiting for #6499 to land first.
I'll create the P-R.

[etienne-lms]

Do you have the xtest side of things?

OP-TEE/optee_test#717

[etienne-lms]

By the way, testing with various configuration settings I saw an optee_os build issue when CFG_TA_STATS=y CFG_WITH_STATS=n. Are you ok I append the fix (proposal) to this P-R or would you prefer a dedicated P-R?

[etienne-lms]

I've rebased on master tip since #6487 has been merged.
Review tag applied.

[jforissier]

By the way, testing with various configuration settings I saw an optee_os build issue when CFG_TA_STATS=y CFG_WITH_STATS=n. Are you ok I append the fix (proposal) to this P-R or would you prefer a dedicated P-R?

Please open a new PR, this one can be merged now. Thanks!