Re: autosleep suspend too frquent problem
From: Pavel Machek
Date: Thu Jun 05 2014 - 09:51:18 EST
On Thu 2014-06-05 14:51:41, Wang, Yalin wrote:
> Thanks for your clarification.
> One problem is the sd card driver itself .
> In addition, I also think kernel's autosleep.c module
> Have problem too.
> It just test wake up count ,if the count is zero, then enter suspend.
> This will result in frequent suspend / resume problems sometimes,
> It is not acceptable, I think also need to be fixed to
> Avoid this special scenario .
Android phones pretty much want to sleep very very often. But if you
think there's coding bug in there, let us know..
> -----Original Message-----
> From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx]
> Sent: Wednesday, June 04, 2014 5:53 AM
> To: Pavel Machek
> Cc: Wang, Yalin; len.brown@xxxxxxxxx; rjw@xxxxxxx; linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-mmc
> Subject: Re: autosleep suspend too frquent problem
> On 3 June 2014 14:01, Pavel Machek <pavel@xxxxxx> wrote:
> > Hi!
> >> I found sd card sometimes are damaged/ destroyed On our devices .
> >> And seems it is caused by kernel's frequently suspend/resume, Because
> >> during suspend/resume, the driver will suspend/resume sdcard Very
> >> frequently, this will damaged the sdcard sometimes, and the damage is
> >> not recoverable ..
> >> Sometimes kernel will enter suspend and exit suspend very frequently,
> >> Especially when the system is in idle, but some driver is not idle,
> >> And it will wake up the system by irq frequently.
> >> By our power test result, if system enter suspend /resume very
> >> frequently, Will consume more power , because it will enable /disable
> >> many devices During a short time .
> >> I make a patch to prevent the system to enter suspend/resume state
> >> More than one time during 2 secondsï
> > It is good you managed to diagnose the problem, but this si not the
> > right solution.
> > Either:
> > 1) don't power down SD card during system suspend
> NAK. The amount of power a card (even if there are good behaving cards as well) may utilize, in powered but idle state could be significant.
> I have seen cases of constant power consumption of several mA here.
> > or maybe even better
> > 2) don't power _up_ SD card during system resume. Let it be powered
> > down until the first access.
> Good news! This is "almost" supported already by the mmc subsystem.
> If your mmc host has set the capability flag MMC_CAP_RUNTIME_RESUME, that means the card won't be powered up (and initialized) until the next request.
> However, for removable cards (!MMC_CAP_NONREMOVABLE), during system resume phase, the mmc core will trigger a "rescan" of the card, to verify it has not been removed. Thus, unfortunate for this use case, the first request (for removable cards) will be triggered during the system resume phase.
> I suppose we should add some extra conditions/flags which makes the mmc core to handle the above scenario. Actually I have been thinking of putting together a patch for this, but it never pops up on the top of my TODO list. :-)
> Additionally, I wonder if this bouncing up and down from suspend to resume, could have other negative impact for other subsystems? Is it just a mmc subsystem problem? I am not so sure.
> Kind regards
> Ulf Hansson
> > Thanks,
> > Pavel
> > --
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> > (cesky, pictures)
> > http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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