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SubjectRe: [PATCH] i2c/designware: enable i2c controller to suspend/resume asynchronously
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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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