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

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Date:	Tue, 5 Jan 2016 10:53:35 +0200
From:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:	"Fu, Zhonghui" <zhonghui.fu@...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

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.

-- 
Jarkko
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