Re: [PATCH v10 2/6] PM / Domains: core changes for multiple states

From: Axel Haslam
Date: Tue Nov 10 2015 - 06:02:38 EST

Hi Zhaoyang,

@@ -576,6 +584,8 @@ static void pm_genpd_sync_poweroff(struct
generic_pm_domain *genpd,
|| atomic_read(&genpd->sd_count) > 0)

+ /* Choose the deepest state when suspending */
+ genpd->state_idx = genpd->state_count - 1;

if there is no governor configured, does it mean that we just try the
deepest one here?

If a governor is not configured, there is no way to choose between the states, and the state_idx will not change. so it will remain the one set at the genpd init function wich is the same as here: the deepest state. (state_count -1). In other words, if there is no governor, there
is only one state: the deepest.

About setting the deepest state in this particular place, My understanding is that this code will be called in suspend path,
and in this case genpd_poweroff is not called, hence the genpd governor is not called either. Because there are many other things happening during suspend/resume, i think that suspend/resume is a slow procedure that will most likely not honor the device qos constraints, so i set the genpd to its deepest state.

genpd_power_off(genpd, timed);

genpd->status = GPD_STATE_POWER_OFF;
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