On 10/11/16 18:54, Gautham R. Shenoy wrote:

From: "Gautham R. Shenoy" <redacted>

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

The previous version can be found here:

[v2]: https://lkml.org/lkml/2016/10/27/143
[v1]: https://lkml.org/lkml/2016/9/29/45

This version fixes a couple of bugs pertaining to strncpy and
initialization of the target-residency values of nap and sleep
which were pointed out by Paul and Oliver in the earlier version.

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.
   

Sounds reasonable

Balbir Singh.