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List:       linux-i2c
Subject:    Re: [PATCH] i2c: designware: Do not allow i2c_dw_xfer() calls while suspended
From:       Grygorii Strashko <grygorii.strashko () ti ! com>
Date:       2018-09-26 22:05:43
Message-ID: 71068c2a-18e3-681c-792a-61a92e49ada9 () ti ! com
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On 09/26/2018 02:40 AM, Hans de Goede wrote:
> Hi,
> 
> On 25-09-18 22:47, Grygorii Strashko wrote:
>>
>>
>> On 09/23/2018 09:00 AM, Hans de Goede wrote:
>>> On most Intel Bay- and Cherry-Trail systems the PMIC is connected 
>>> over I2C
>>> and the PMIC is accessed through various means by the _PS0 and _PS3 ACPI
>>> methods (power on / off methods) of various devices.
>>>
>>> This leads to suspend/resume ordering problems where a device may be
>>> resumed and get its _PS0 method executed before the I2C controller is
>>> resumed. On Cherry Trail this leads to errors like these:
>>>
>>>       i2c_designware 808622C1:06: controller timed out
>>>       ACPI Error: AE_ERROR, Returned by Handler for [UserDefinedRegion]
>>>       ACPI Error: Method parse/execution failed \_SB.P18W._ON, AE_ERROR
>>>       video LNXVIDEO:00: Failed to change power state to D0
>>>
>>
>> Hm. There should some dependency from PM domain (or smth. like this) 
>> which, in turn should depends from i2c.
> 
> Yes and I've a patchset pending to fix the dependency missing in this
> specific case. But there might be other cases where we miss the dependency
> the idea behind this patch / behind the generic solution Wolfram is
> working on which will replace this patch / is to make it easier to
> catch/debug cases where such a dependency is missing.

Thanks for explanation, It might be good to update commit message  
and pay attention that this is not just w/a, but debug instrument.

Note. it will help catch not only dependency issues, but also buggy
drivers who left workers/kthreads/irq threads enabled while suspending and
which might run on other CPUs in parallel with suspend process
until suspend_enter()->disable_nonboot_cpus() call.


-- 
regards,
-grygorii
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