On 04/10/16 21:32, Michael Ellerman wrote:

"Gautham R. Shenoy" [off-list ref] writes:

quoted

From: "Gautham R. Shenoy" <redacted>

The power9_idle_stop method currently takes only the requested stop
level as a parameter and picks up the rest of the PSSCR bits from a
hand-coded macro. This is not a very flexible design, especially when
the firmware has the capability to communicate the psscr value and the
mask associated with a particular stop state via device tree.

This patch modifies the power9_idle_stop API to take as parameters the
PSSCR value and the PSSCR mask corresponding to the stop state that
needs to be set. These PSSCR value and mask are respectively obtained
by parsing the "ibm,cpu-idle-state-psscr" and
"ibm,cpu-idle-state-psscr-mask" fields from the device tree.

In addition to this, the patch adds support for handling stop states
for which ESL and EC bits in the PSSCR are zero. As per the
architecture, a wakeup from these stop states resumes execution from
the subsequent instruction as opposed to waking up at the System
Vector.

That looks good.

quoted

This patch depends on the following skiboot patch that exports the
PSSCR values and the mask for all the stop states:
https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html

But we can't depend on a skiboot patch. The kernel has to cope with
running on an old skiboot.

Hi, Michael

I think with an older skiboot the flags don't get exported and the
new cpuidle (stop state) does not get discovered. I don't think there
is any breakage. Gautham am I missing something?

Balbir Singh.