Re: Question about suspend/resume clock handling in dwc3-of-simple.c

From: Felipe Balbi
Date: Mon Sep 12 2016 - 15:05:26 EST

Hi Guenter,

Guenter Roeck <linux@xxxxxxxxxxxx> writes:
> Hi folks,
> In dwc3-of-simple.c:dwc3_of_simple_remove(), I see the following code.
> for (i = 0; i < simple->num_clocks; i++) {
> clk_unprepare(simple->clks[i]);
> clk_put(simple->clks[i]);
> }
> What I don't understand is why clk_unprepare() is called instead
> of clk_disable_unprepare(). Someone told me that it was due to
> dwc3_of_simple_runtime_suspend(), which would call clk_disable().

good eyes :-) That was fixed though:

> Should it be clk_disable_unprepare(), or maybe something like the
> following
> if (!pm_runtime_status_suspended(dev))
> clk_disable_unprepare();
> else
> clk_unprepare();

I'm not sure how balanced those calls are, yeah. I don't have HW to test
PM with. But note that as it is, there is no actual runtime PM support,
so clk_disable_unprepare() will always be necessary.

Perhaps we will find further issues when someone tries to use runtime PM
with dwc3-of-simple. ;-)


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