[PATCH v6 0/5] powernv:stop: Use psscr_val,mask provided by firmware

From: Gautham R. Shenoy
Date: Wed Jan 25 2017 - 03:38:31 EST

From: "Gautham R. Shenoy" <ego@xxxxxxxxxxxxxxxxxx>

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

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
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:

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