Re: [PATCH] i2c: rk3x: keep i2c irq ON in suspend

[David.Wu]

Hi Grygorii, Doug and Heiko,

Thanks for your replies.
I will do 2 steps:

1. Add "suspended" flag in suspend_noirq()/resume_noirq() callback to 
prevent new i2c started, and use i2c_lock_adapter() to wait for current 
i2c transfer finished.

2. IRQF_NO_SUSPEND added could make i2c work well during the time 
between suspend_device_irqs() and i2c_suspend_noirq() callback. In the 
other side, it is the the time between resume_device_irqs() and 
i2c_resume_noirq() callback.

If any i2c client try to access I2C after suspend_noirq() or before 
resume_noirq() callback, print the warning, and they should fix it, not 
to start i2c access and the moment.

å 2016/12/8 0:27, Grygorii Strashko åé:
> On 12/06/2016 09:37 PM, David.Wu wrote:
> > Hi Doug,
> >
> > å 2016/12/7 0:31, Doug Anderson åé:
> > > Hi,
> > >
> > > On Tue, Dec 6, 2016 at 12:12 AM, David.Wu <david.wu@xxxxxxxxxxxxxx>
> > > wrote:
> > > > Hi Heiko,
> > > >
> > > > å 2016/12/5 18:54, Heiko Stuebner åé:
> > > > > Hi David,
> > > > >
> > > > > Am Montag, 5. Dezember 2016, 16:02:59 CET schrieb David Wu:
> > > > > > During suspend there may still be some i2c access happening.
> > > > > > And if we don't keep i2c irq ON, there may be i2c access timeout if
> > > > > > i2c is in irq mode of operation.
> > > > >
> > > > >
> > > > > can you describe the issue you're trying to fix a bit more please?
> > > >
> > > >
> > > > Sometimes we could see the i2c timeout errors during suspend/resume,
> > > > which
> > > > makes the duration of suspend/resume too longer.
> > > >
> > > > [  484.171541] CPU4: Booted secondary processor [410fd082]
> > > > [  485.172777] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
> > > > [  486.172760] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
> > > > [  487.172759] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
> > > > [  487.172840] cpu cpu4: _set_opp_voltage: failed to set voltage (800000
> > > > 800000 800000 mV): -110
> > > > [  487.172874] cpu cpu4: failed to set volt 800000
> > > >
> > > > > I.e. I'd think the i2c-core does suspend i2c-client devices first,
> > > > > so that
> > > > > these should be able to finish up their ongoing transfers and not start
> > > > > any
> > > > > new ones instead?
> > > > >
> > > > > Your irq can still happen slightly after the system started going to
> > > > > actually
> > > > > sleep, so to me it looks like you just widened the window where irqs
> > > > > can
> > > > > be
> > > > > handled. Especially as your irq could also just simply stem from the
> > > > > start
> > > > > state, so you cannot even be sure if your transaction actually is
> > > > > finished.
> > > >
> > > >
> > > > Okay, you are right. I want to give it a double insurance at first,
> > > > but it
> > > > may hide the unhappend issue.
> > > >
> > > > > So to me it looks like the i2c-connected device driver should be fixed
> > > > > instead?
> > > >
> > > >
> > > > I tell them to fix it in rk808 driver.
> > >
> > > To me it seems like perhaps cpufreq should not be changing frequencies
> > > until it is resumed properly.  Presumably if all the ordering is done
> > > right then cpufreq should be resumed _after_ the i2c regulator so you
> > > should be OK.  ...or am I somehow confused about that?
> >
> > yesïthe cpufreq and regulator should start i2c job after they resume
> > properly.
> >
> > > Also note that previous i2c busses I worked with simply returned -EIO
> > > in the case where they were called when suspended.  See
> > > "i2c-exynos5.c" and "i2c-s3c2410.c".
> >
> > In "i2c-exynos5.c", it seems that using the "i2c->suspended" to protect
> > i2c transfer works most of the time. Of course it could prevent the next
> > new i2c transfer to start. But in one case, if the current i2c job was
> > not finished until the i2c irq was disabled by system suspend, the i2c
> > timeout error would also happen, as the current i2c job may have a large
> > data to transfer and it lasts from a long time.
>
> And this means you have bug in some of I2C client drivers which do not stop
> their activities during suspend properly (most usual case - driver uses work
> and this work still active during suspend and can run on one CPU while suspend
> runs on another).
>
> At the moment .suspend_noirq() callback is called there should be no active
> I2C transactions in general.
>
> > So is it necessary to add a mutex lock to wait the current job to be
> > finished before the "i2c->suspended" is changed in i2c_suspend_noirq()?
>
> You need to catch and fix all driver who will try to access I2C after your
> I2C bus driver passes suspend_noirq stage. Smth, like [1], uses i2c_lock_adapter().
>
>
> [1] https://git.ti.com/android-sdk/kernel-omap/commit/125ef8f7016e7b205886f93862288a45a312b1d8