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

["David.Wu" <david.wu@rock-chips.com>]

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.

在 2016/12/8 0:27, Grygorii Strashko 写道:
>
>
> On 12/06/2016 09:37 PM, David.Wu wrote:
>> Hi Doug,
>>
>> 在 2016/12/7 0:31, Doug Anderson 写道:
>>> Hi,
>>>
>>> On Tue, Dec 6, 2016 at 12:12 AM, David.Wu <david.wu@rock-chips.com>
>>> wrote:
>>>> Hi Heiko,
>>>>
>>>> 在 2016/12/5 18:54, Heiko Stuebner 写道:
>>>>>
>>>>> 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?
>>
>> yes，the 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
>