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.

? 2016/12/8 0:27, Grygorii Strashko ??:

On 12/06/2016 09:37 PM, David.Wu wrote:

quoted

Hi Doug,

? 2016/12/7 0:31, Doug Anderson ??:

quoted

Hi,

On Tue, Dec 6, 2016 at 12:12 AM, David.Wu [off-list ref]
wrote:

quoted

Hi Heiko,

? 2016/12/5 18:54, Heiko Stuebner ??:

quoted

Hi David,

Am Montag, 5. Dezember 2016, 16:02:59 CET schrieb David Wu:

quoted

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

quoted

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.

quoted

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?

yes?the cpufreq and regulator should start i2c job after they resume
properly.

quoted

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.

quoted

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