powernv:stop: Use psscr_val,mask provided by firmware

From: "Gautham R. Shenoy" <[email protected]>

This is the sixth iteration of the patchset to use the psscr_val and psscr_mask provided by the firmware for each of the stop states.

The previous versions can be found here:
[v5]: https://lkml.org/lkml/2017/1/10/147
[v4]: https://lkml.org/lkml/2016/12/9/288
[v3]: https://lkml.org/lkml/2016/11/10/37
[v2]: https://lkml.org/lkml/2016/10/27/143
[v1]: https://lkml.org/lkml/2016/9/29/45

This version addresses the feedback provided by Balbir and Rob Herring to v5. The key changes are:

- [PATCH 2] Rename pnv_arch300_idle_init to pnv_power9_idle_init to be consistent with the nomenclature of variables and functions in idle_book3s.S.

- [PATCH 5] Updated the introduction to Idle-state properties in the devicetree bindings documentation in order to clarify when the "name" and "flags" properties are required. Also fixed the typos in the Documentation for the device-tree bindings

Synopsis
==========
In the current implementation, the code for ISA v3.0 stop implementation has a couple of shortcomings.

a) The code hand-codes the values for ESL, EC, TR, MTL bits of PSSCR and uses only the RL field from the firmware. While this is not incorrect, since the hand-coded values are legitimate, it is not a very flexible design since the firmware has the capability to communicate these values via the "ibm,cpu-idle-state-psscr" and "ibm,cpu-idle-state-psscr-mask" properties. In case where the firmware provides values for these fields that is different from the hand-coded values, the current code will not work as intended.

b) Due to issue a), the current code assumes that ESL=EC=1 for all the stop states and hence the wakeup from the stop instruction will happen at 0x100, the system-reset vector. However, the ISA v3.0 allows the ESL=EC=0 behaviour where the corresponding stop-state loses no state and wakes up from the subsequent instruction. The current code doesn't handle this case.

This patch series addresses these issues.

The first patch in the series renames the existing IDLE_STATE_ENTER_SEQ macro to IDLE_STATE_ENTER_SEQ_NORET. It reuses the name IDLE_STATE_ENTER_SEQ for entering into stop-states which wake up at the subsequent instruction.

The second patch in the series renames pnv_arch300_idle_init() to pnv_power9_idle_init.

The third patch adds a helper function in cpuidle-powernv.c for initializing entries of the powernv_states[] table that is passed to the cpu-idle core. This eliminates some of the code duplication in the function that discovers and initializes the stop states.

The fourth patch in the series fixes issues a) and b) by ensuring that the psscr-value and the psscr-mask provided by the firmware are what will be used to set a particular stop state. It also adds support for handling wake-up from stop states which were entered with ESL=EC=0. It validates hat the psscr values exposed by the firmware maintains the invariants mentioned in the ISA.

The fourth patch also handles the older firmware which sets only the Requested Level (RL) field in the psscr and psscr-mask exposed in the device tree. In the presence of such older firmware, this patch will set the default sane values for for remaining PSSCR fields (i.e PSLL, MTL, ESL, EC, and TR).

The fifth patch provides the documentation for the device-tree bindings describing the idle state properties under the @power-mgt node in the device-tree.

The skiboot patch populates all the relevant fields in the PSSCR values and the mask for all the stop states can be found here:
https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html

Gautham R. Shenoy (5):
powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro powernv:stop: Rename pnv_arch300_idle_init to pnv_power9_idle_init cpuidle:powernv: Add helper function to populate powernv idle states.
powernv: Pass PSSCR value and mask to power9_idle_stop Documentation:powerpc: Add device-tree bindings for power-mgt

 .../devicetree/bindings/powerpc/opal/power-mgt.txt | 118 +++++++++++++++++
 arch/powerpc/include/asm/cpuidle.h                 |  49 ++++++-
 arch/powerpc/include/asm/processor.h               |   3 +-
 arch/powerpc/kernel/exceptions-64s.S               |   6 +-
 arch/powerpc/kernel/idle_book3s.S                  |  40 +++---
 arch/powerpc/platforms/powernv/idle.c              | 142 ++++++++++++++++++---
 arch/powerpc/platforms/powernv/powernv.h           |   3 +-
 arch/powerpc/platforms/powernv/smp.c               |  14 +-
 drivers/cpuidle/cpuidle-powernv.c                  | 129 +++++++++++++------
 include/linux/cpuidle.h                            |   1 +
 10 files changed, 421 insertions(+), 84 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt

1.9.4