linux-kernel - Re: [PATCH] PM / Clocks: fix pm_clk_resume/suspend if CONFIG_PM

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Message-ID: <528D1784.8080704@ti.com>
Date:	Wed, 20 Nov 2013 22:11:48 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	<santosh.shilimkar@...com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>
Subject: Re: [PATCH] PM / Clocks: fix pm_clk_resume/suspend if CONFIG_PM_RUNTIME
 is set

On 11/20/2013 09:53 PM, Stephen Boyd wrote:
> On 11/20/13 11:06, Grygorii Strashko wrote:
>> On 11/20/2013 08:42 PM, Stephen Boyd wrote:
>>> On 11/20/13 05:31, Grygorii Strashko wrote:
>>>> @@ -230,7 +230,7 @@ int pm_clk_suspend(struct device *dev)
>>>>    	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
>>>>    		if (ce->status < PCE_STATUS_ERROR) {
>>>>    			if (ce->status == PCE_STATUS_ENABLED)
>>>> -				clk_disable(ce->clk);
>>>> +				clk_disable_unprepare(ce->clk);
>>>>    			ce->status = PCE_STATUS_ACQUIRED;
>>>>    		}
>>>>    	}
>>>> @@ -259,7 +259,7 @@ int pm_clk_resume(struct device *dev)
>>>>    
>>>>    	list_for_each_entry(ce, &psd->clock_list, node) {
>>>>    		if (ce->status < PCE_STATUS_ERROR) {
>>>> -			clk_enable(ce->clk);
>>>> +			clk_prepare_enable(ce->clk);
>>>>    			ce->status = PCE_STATUS_ENABLED;
>>>>    		}
>>>>    	}
>>> This is inside a spin_lock_irqsave(). You should be getting scheduling
>>> while atomic warnings with this change. Are you testing with
>>> DEBUG_ATOMIC_SLEEP=y?
>> Ops, thanks. No, It's not tested with DEBUG_ATOMIC_SLEEP and
>> I agree with you.
>>
>> So, I see two option here:
>> 1) split above loops on two
>> 2) add calls of clk_prepare()/clk_unprepare() in pm_clk_notify()
>>
>> In my opinion option [2] is better.
>>
> 
> Doesn't that mean the clock will always be prepared as long as the
> device is present? That doesn't sound good. I would like the clocks to
> be disabled and unprepared as long as the device is suspended.

Yep (

> 
> What is the lock protecting? The linked list or something more? Can we
> remove the locks?

Looks like it's protecting linked list pm_clock_entry'es.

> 
> It looks like even if you just remove the locks here, the PM core is
> free to call this function with irqs disabled if pm_runtime_irq_safe()
> has been called on the device. Perhaps runtime PM can only do the
> clk_enable()/clk_disable() part and the clk_unprepare()/clk_prepare()
> calls should happen in the system suspend callbacks?

Even don't know what to say :( On Keystone clk_unprepare()/clk_prepare() are NOPs.
But clk_prepare() has to be called at least once before clk_enable() :((
So, solution with suspend/resume will not fix current problem :( unfortunately.

FYI, Now pm_clk_suspend/pm_clk_resume are called from arch/arm/mach-keystone/pm_domain.c
(also similar solution is used by Davinci, but issue has not been detected because
PM runtime hasn't been used by Davinci IP drivers before)

Regards,
- grygorii


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