[PATCH] powerpc/powernv/idle: add a basic stop 0-3 driver for POWER10

[Vaidyanathan Srinivasan]

* Nicholas Piggin <npiggin at gmail.com> [2020-08-19 19:47:00]:

> This driver does not restore stop > 3 state, so it limits itself
> to states which do not lose full state or TB.
> 
> The POWER10 SPRs are sufficiently different from P9 that it seems
> easier to split out the P10 code. The POWER10 deep sleep code
> (e.g., the BHRB restore) has been taken out, but it can be re-added
> when stop > 3 support is added.
> 
> Cc: Ryan P Grimm <rgrimm at us.ibm.com>
> Cc: Michael Neuling <mikey at neuling.org>
> Cc: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> Cc: Pratik Rajesh Sampat <psampat at linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>


Tested-by: Vaidyanathan Srinivasan <svaidy at linux.ibm.com>

This patch series was tested on P9 and P10. Correct set of
stop states were discovered and enabled in the platform.

Further the SPRs saved and restored by this code has also been
tested along with cpuidle state tests and cpu offline/online tests.

Thank for patch.

--Vaidy