On Wed, May 08, 2019 at 08:28:30PM +0000, mario.limoncie...@dell.com wrote:
> You might think this would be adding runtime_suspend/runtime_resume
> callbacks, but those also get called actually at runtime which is not
> the goal here. At runtime, these types of disks should rely on APST which
> should calculate the appropriate latencies around the different power states.
>
> This code path is only applicable in the suspend to idle state, which /does/
> call suspend/resume functions associated with dev_pm_ops. There isn't
> a dedicated function in there for use only in suspend to idle, which is
> why pm_suspend_via_s2idle() needs to get called.
The problem is that it also gets called for others paths:
#ifdef CONFIG_PM_SLEEP
#define SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
.suspend = suspend_fn, \
.resume = resume_fn, \
.freeze = suspend_fn, \
.thaw = resume_fn, \
.poweroff = suspend_fn, \
.restore = resume_fn,
#else
else
#define SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn)
#endif
#define SIMPLE_DEV_PM_OPS(name, suspend_fn, resume_fn) \
const struct dev_pm_ops name = { \
SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn) \
}
And at least for poweroff this new code seems completely wrong, even
for freeze it looks rather borderline.
And more to the points - if these "modern MS standby" systems are
becoming common, which it looks they are, we need support in the PM core
for those instead of working around the decisions in low-level drivers.
> SIMPLE_DEV_PM_OPS normally sets the same function for suspend and
> freeze (hibernate), so to avoid any changes to the hibernate case it seems
> to me that there needs to be a new nvme_freeze() that calls into the existing
> nvme_dev_disable for the freeze pm op and nvme_thaw() that calls into the
> existing nvme_reset_ctrl for the thaw pm op.
At least, yes.
>
> > enterprise class NVMe devices
> > that don't do APST and don't really do different power states at
> > all in many cases.
>
> Enterprise class NVMe devices that don't do APST - do they typically
> have a non-zero value for ndev->ctrl.npss?
>
> If not, they wouldn't enter this new codepath even if the server entered into
> S2I.
No, devices that do set NPSS will have at least some power states
per definition, although they might not be too useful. I suspect checking
APSTA might be safer, but if we don't want to rely on APST we should
check for a power state supporting the condition that the MS document
quoted in the original document supports.
