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

[David.Wu]

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.

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()?

However, the i2c_suspend_noirq() is called after suspend_device_irqs() 
in system suspend, it means that the i2c timeout errors could happen 
during the time between suspend_device_irqs() and i2c_suspend_noirq(), 
if there were i2c transfers started.

> -Doug