On Tue, 8 Oct 2024 at 20:25, Rafael J. Wysocki rafael@kernel.org wrote:
On Tue, Oct 8, 2024 at 12:35 AM Ulf Hansson ulf.hansson@linaro.org wrote:
On Tue, 8 Oct 2024 at 00:25, Laurent Pinchart laurent.pinchart@ideasonboard.com wrote:
Hi Ulf,
On Tue, Oct 08, 2024 at 12:08:24AM +0200, Ulf Hansson wrote:
On Mon, 7 Oct 2024 at 20:49, Laurent Pinchart wrote:
On Fri, Oct 04, 2024 at 04:38:36PM +0200, Ulf Hansson wrote:
On Fri, 4 Oct 2024 at 11:41, Sakari Ailus wrote: > > Hello everyone, > > This set will switch the users of pm_runtime_put_autosuspend() to > __pm_runtime_put_autosuspend() while the former will soon be re-purposed > to include a call to pm_runtime_mark_last_busy(). The two are almost > always used together, apart from bugs which are likely common. Going > forward, most new users should be using pm_runtime_put_autosuspend(). > > Once this conversion is done and pm_runtime_put_autosuspend() re-purposed, > I'll post another set to merge the calls to __pm_runtime_put_autosuspend() > and pm_runtime_mark_last_busy().
That sounds like it could cause a lot of churns.
Why not add a new helper function that does the pm_runtime_put_autosuspend() and the pm_runtime_mark_last_busy() things? Then we can start moving users over to this new interface, rather than having this intermediate step?
I think the API would be nicer if we used the shortest and simplest function names for the most common use cases. Following pm_runtime_put_autosuspend() with pm_runtime_mark_last_busy() is that most common use case. That's why I like Sakari's approach of repurposing pm_runtime_put_autosuspend(), and introducing __pm_runtime_put_autosuspend() for the odd cases where pm_runtime_mark_last_busy() shouldn't be called.
Okay, so the reason for this approach is because we couldn't find a short and descriptive name that could be used in favor of pm_runtime_put_autosuspend(). Let me throw some ideas at it and maybe you like it - or not. :-)
I like the idea at least :-)
I don't know what options you guys discussed, but to me the entire "autosuspend"-suffix isn't really that necessary in my opinion. There are more ways than calling pm_runtime_put_autosuspend() that triggers us to use the RPM_AUTO flag for rpm_suspend(). For example, just calling pm_runtime_put() has the similar effect.
To be honest, I'm lost there. pm_runtime_put() calls __pm_runtime_idle(RPM_GET_PUT | RPM_ASYNC), while pm_runtime_put_autosuspend() calls __pm_runtime_suspend(RPM_GET_PUT | RPM_ASYNC | RPM_AUTO).
__pm_runtime_idle() ends up calling rpm_idle(), which may call rpm_suspend() - if it succeeds to idle the device. In that case, it tags on the RPM_AUTO flag in the call to rpm_suspend(). Quite similar to what is happening when calling pm_runtime_put_autosuspend().
Right.
For almost everybody, except for a small bunch of drivers that actually have a .runtime_idle() callback, pm_runtime_put() is literally equivalent to pm_runtime_put_autosuspend().
So really the question is why anyone who doesn't provide a .runtime_idle() callback bothers with using this special pm_runtime_put_autosuspend() thing, which really means "do a runtime_put(), but skip my .runtime_idle() callback".
My guess is that it's in most cases a legacy pattern that is being followed. Also note that rpm_idle() didn't "always" tag on the RPM_AUTO flag, even if it's quite a while ago (2013) since we added it.
Unless there is some actual optimization involved, as it also allows us to skip calling rpm_idle() and go directly for rpm_suspend().
Moreover, it's similar for pm_runtime_mark_last_busy(), it's called during rpm_resume() too, for example. So why bother about having "mark_last_busy" in the new name too.
That said, my suggestion is simply "pm_runtime_put_suspend".
Can we do even better, and make pm_runtime_put() to handle autosuspend automatically when autosuspend is enabled ?
As stated above, this is already the case.
What really is needed appears to be a combination of pm_runtime_mark_last_busy() with pm_runtime_put().
This makes sense to me too, but I don't think we should limit it to this.
Making pm_runtime_put_autosuspend (or if the name "pm_runtime_put_suspend" is better?) to do the similar thing, is probably a good idea too. At least in my opinion.
Granted, pm_runtime_put() could do the pm_runtime_mark_last_busy() thing automatically if autosuspend is enabled and the only consequence of it might be delaying a suspend of the device until its autosuspend timer expires, which should not be a problem in the vast majority of cases.
Right.
I guess we should expect the *sync* variants to be used, if the timer really needs to be overridden.
Kind regards Uffe