| Message ID | 20210118011330.4145-2-digetx@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3,1/3] PM: domains: Make set_performance_state() callback optional | expand |
On 18-01-21, 04:13, Dmitry Osipenko wrote: > Make set_performance_state() callback optional in order to remove the > need from power domain drivers to implement a dummy callback. If callback > isn't implemented by a GENPD driver, then the performance state is passed > to the parent domain. > > Tested-by: Peter Geis <pgwipeout@gmail.com> > Tested-by: Nicolas Chauvet <kwizart@gmail.com> > Tested-by: Matt Merhar <mattmerhar@protonmail.com> > Suggested-by: Ulf Hansson <ulf.hansson@linaro.org> > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > --- > drivers/base/power/domain.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > index 9a14eedacb92..a3e1bfc233d4 100644 > --- a/drivers/base/power/domain.c > +++ b/drivers/base/power/domain.c > @@ -339,9 +339,11 @@ static int _genpd_set_performance_state(struct generic_pm_domain *genpd, > goto err; > } > > - ret = genpd->set_performance_state(genpd, state); > - if (ret) > - goto err; > + if (genpd->set_performance_state) { > + ret = genpd->set_performance_state(genpd, state); > + if (ret) > + goto err; > + } Earlier in this routine we also have this: if (!parent->set_performance_state) continue; Should we change that too ? > > genpd->performance_state = state; > return 0; > @@ -399,9 +401,6 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state) > if (!genpd) > return -ENODEV; > > - if (unlikely(!genpd->set_performance_state)) > - return -EINVAL; > - > if (WARN_ON(!dev->power.subsys_data || > !dev->power.subsys_data->domain_data)) > return -EINVAL; Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
On 18-01-21, 13:46, Ulf Hansson wrote: > You seem to be worried about latency/overhead while doing the > propagation upwards in the hierarchy. That seems like a reasonable > concern to me, especially as the genpd lock is taken at each level. I am not sure how many levels of domains we have normally, but unless the number is big it won't be a very big problem. > However, to mitigate this can be rather messy. In principle, we would > need to walk the hierarchy upwards, each time a new subdomain is added > in genpd_add_subdomain(). While doing this, we would also need to keep > track on what level we set to continue the propagation of the > performance states for. Even if this can be done in non-latency > sensitive paths, I don't think it's worth it because of complexity (I > haven't even thought of what happens when removing a subdomain). What about a new field in the domain structure like 'can-handle-pstates', and then whenever sub-domain gets added it just needs to check its parent's field and set his own. > So, maybe we should simply just stick to the existing code, forcing > the parent to have a ->set_performance() callback assigned if > propagation should continue? I think it would be better to fix the issue even if we aren't fully optimized and making the change to make sure we keep propagating is rather important. -- viresh
On Tue, 19 Jan 2021 at 04:44, Viresh Kumar <viresh.kumar@linaro.org> wrote: > > On 18-01-21, 13:46, Ulf Hansson wrote: > > You seem to be worried about latency/overhead while doing the > > propagation upwards in the hierarchy. That seems like a reasonable > > concern to me, especially as the genpd lock is taken at each level. > > I am not sure how many levels of domains we have normally, but unless the number > is big it won't be a very big problem. It depends on the SoC topology, so obviously it differs. But more than a couple is unusual, I would say. However, I think it may also depend on how many devices that are hooked up to the domains and how actively these are being used. > > > However, to mitigate this can be rather messy. In principle, we would > > need to walk the hierarchy upwards, each time a new subdomain is added > > in genpd_add_subdomain(). While doing this, we would also need to keep > > track on what level we set to continue the propagation of the > > performance states for. Even if this can be done in non-latency > > sensitive paths, I don't think it's worth it because of complexity (I > > haven't even thought of what happens when removing a subdomain). > > What about a new field in the domain structure like 'can-handle-pstates', and > then whenever sub-domain gets added it just needs to check its parent's field > and set his own. That would work if the topology is built from top to bottom, but I don't think we can rely on that. For example, when a domain A is added as a child to domain B, domain B doesn't have a parent yet (and the "can-handle-pstates" don't get set for neither domain A or domain B). Next, domain B is added as child domain to domain C. Domain C has the "can-handle-pstates" set, which means domain B gets the "can-handle-pstates" set as well. This means domain A, will not have "can-handle-pstates" set, while it probably should have. > > > So, maybe we should simply just stick to the existing code, forcing > > the parent to have a ->set_performance() callback assigned if > > propagation should continue? > > I think it would be better to fix the issue even if we aren't fully optimized > and making the change to make sure we keep propagating is rather important. Alright, let's continue with Dmitry's patches and discuss this further when v4 is out, as he seems to have it almost ready. Kind regards Uffe
On 19-01-21, 10:52, Ulf Hansson wrote: > That would work if the topology is built from top to bottom, but I > don't think we can rely on that. > > For example, when a domain A is added as a child to domain B, domain B > doesn't have a parent yet (and the "can-handle-pstates" don't get set > for neither domain A or domain B). Next, domain B is added as child > domain to domain C. Domain C has the "can-handle-pstates" set, which > means domain B gets the "can-handle-pstates" set as well. This means > domain A, will not have "can-handle-pstates" set, while it probably > should have. Okay, I missed that part. > > > > > So, maybe we should simply just stick to the existing code, forcing > > > the parent to have a ->set_performance() callback assigned if > > > propagation should continue? > > > > I think it would be better to fix the issue even if we aren't fully optimized > > and making the change to make sure we keep propagating is rather important. > > Alright, let's continue with Dmitry's patches and discuss this further > when v4 is out, as he seems to have it almost ready. Right. -- viresh
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 9a14eedacb92..a3e1bfc233d4 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -339,9 +339,11 @@ static int _genpd_set_performance_state(struct generic_pm_domain *genpd, goto err; } - ret = genpd->set_performance_state(genpd, state); - if (ret) - goto err; + if (genpd->set_performance_state) { + ret = genpd->set_performance_state(genpd, state); + if (ret) + goto err; + } genpd->performance_state = state; return 0; @@ -399,9 +401,6 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state) if (!genpd) return -ENODEV; - if (unlikely(!genpd->set_performance_state)) - return -EINVAL; - if (WARN_ON(!dev->power.subsys_data || !dev->power.subsys_data->domain_data)) return -EINVAL;