On Sun, 23 Nov 2014, liu chunlin wrote:
> Hi all,
>
> AS I known,SDcard use SDIO interface,I need use a sdcard-reader( USB to
> SDIO)if I want to use sdcard on my board ,but I have try many sdcard-reader
> without sdcard to connect usb ,all of them will cause usb bus can't enter
> runtime suspend. and I try to connect a usb storage on my demo board also
> will cause usb bus can't enter runtime suspend,but if I press power
> button,the usb bus can enter suspend mode.I guess the driver hav not
> implemented this function.
>
> Alan Stern tell me that Runtime suspend for USB storage devices was added in
> the 3.14 kernel,but I can't find the patches about USB runtime.Who can help
> me?
I was wrong; the support was added in the 3.10 kernel by these commits:
66311274691e
6c9546675864
c8158819d506
9b21493c4520
6df339a51e3b
with bug fixes in these commits:
d20ec597cba1
c60855cdb976
10c580e4239d
In order to make runtime suspend work, you have to turn off
media-change polling. When there's no card in the reader, the system
will constantly check to see if a card has been inserted. This
checking will prevent the device from entering runtime suspend.
Alan Stern
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