linux-kernel - Re: [PATCH] i2c/designware: enable i2c controller to suspend/resume asynchronously

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Date:	Fri, 15 Jan 2016 14:42:42 +0800
From:	"Fu, Zhonghui" <zhonghui.fu@...ux.intel.com>
To:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-i2c@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	srinivas.kowtal@...el.com
Subject: Re: [PATCH] i2c/designware: enable i2c controller to suspend/resume
 asynchronously



On 1/5/2016 4:53 PM, Jarkko Nikula wrote:
> Hi
>
> On 12/24/2015 04:30 PM, Fu, Zhonghui wrote:
>> Now, PM core supports asynchronous suspend/resume mode for devices
>> during system suspend/resume, and the power state transition of one
>> device may be completed in separate kernel thread. PM core ensures
>> all power state transition dependency between devices. This patch
>> enables designware i2c controllers to suspend/resume asynchronously.
>> This will take advantage of multicore and improve system suspend/resume
>> speed. After enabling all i2c devices, i2c adapters and i2c controllers
>> on ASUS T100TA tablet, the system suspend-to-idle time is reduced to
>> about 510ms from 750ms, and the system resume time is reduced to about
>> 790ms from 900ms.
>>
> Nice reduction :-)
>
>> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
>> index 6b00061..395130b 100644
>> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
>> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
>> @@ -230,6 +230,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>>       }
>>
>>       adap = &dev->adapter;
>> +    device_enable_async_suspend(&pdev->dev);
>>       adap->owner = THIS_MODULE;
>>       adap->class = I2C_CLASS_DEPRECATED;
>>       ACPI_COMPANION_SET(&adap->dev, ACPI_COMPANION(&pdev->dev));
>
> Does device_enable_async_suspend() need to be called before enabling runtime PM? I suppose not since there appears to have also related sysfs node for toggling it runtime.
>
> I'm thinking if you could move the device_enable_async_suspend() call into drivers/i2c/busses/i2c-designware-core.c: i2c_dw_probe() and then also PCI enumerated adapter could take advantage of it.

Because of long leave, so sorry for late reply.

Your proposal is right. I have submitted a new patch according to your comments - "[PATCH v2] i2c/designware: enable i2c controller to suspend/resume asynchronously".


Thanks,
Zhonghui