18.08.2021 08:58, Viresh Kumar пишет: > On 18-08-21, 08:21, Dmitry Osipenko wrote: >> Yes, GENPD will cache the perf state across suspend/resume and initially >> cached value is out of sync with h/w. >> >> Nothing else. But let me clarify it all again. > > Thanks for your explanation. > >> Initially the performance state of all GENPDs is 0 for all devices. >> >> The clock rate is preinitialized for all devices to a some default rate >> by clk driver, or by bootloader or by assigned-clocks in DT. >> >> When device is rpm-resumed, the resume callback of a device driver >> enables the clock. >> >> Before clock is enabled, the voltage needs to be configured in >> accordance to the clk rate. >> >> So now we have a GENPD with pstate=0 on a first rpm-resume, which >> doesn't match the h/w configuration. Calling dev_pm_opp_sync() sets the >> pstate in accordance to the h/w config. > > What about calling dev_pm_opp_set_rate(dev, clk_get_rate(dev)) here > instead ? That will work, right ? The advantage is it works without > any special routine to do so. It will work, but a dedicated helper is nicer. > I also wonder looking at your gr3d.c changes, you set a set-opp > helper, but the driver doesn't call set_opp_rate at all. Who calls it > ? dev_pm_opp_sync() calls it from _set_opp(). > And if it is all about just syncing the genpd core, then can the genpd > core do something like what clk framework does? i.e. allow a new > optional genpd callback, get_performance_state() (just like > set_performance_state()), which can be called initially by the core to > get the performance to something other than zero. opp-set-rate is > there to set the performance state and enable the stuff as well. > That's why it looks incorrect in your case, where the function was > only required to be called once, and you are ending up calling it on > each resume. Limiting that with another local variable is bad as well. We discussed variant with get_performance_state() previously and Ulf didn't like it either since it still requires to touch 'internals' of GENPD.
