Re: [RFC PATCH] usb/acpi: Add support usb port power off mechanism for device fixed on the motherboard

Lan Tianyu
2012-05-11T18:24:14Z

On 2012年05月12日 01:44, Alan Stern wrote:
> On Sat, 12 May 2012, Lan Tianyu wrote:
>
>> The power saving depends on devices. I test a usb3.0 ssd. The power saving of
>> power off is about 2.2w more than just selective suspend. In theory, power
>> off can help to save remaining power after selective suspend.
>
> That's a lot of power! Suspended USB devices aren't supposed to
> consume more than 2.5 mA of bus current, which at 5 V amounts to<=
> 0.0125 W. Does the port really use that much? Or does the SSD have a
> separate power supply that it disables when port power is removed?

The device consumes about 3.1w. The selective suspend can cut down 0.7-0.9w
After power off port, all power will removed.
I test all the motherboard power consumption and get the result.
From lsusb, it's self-powered.

lsusb
Bus 003 Device 006: ID 174c:55aa ASMedia Technology Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x174c ASMedia Technology Inc.
idProduct 0x55aa
bcdDevice 1.00
iManufacturer 2 01234567890123456789012345678901234567890123
iProduct 3 012345678901234567890123456789012345678901234567
iSerial 1 0123456789ABCDEF019F
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 0mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk (Zip)
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Device Status: 0x0001
Self Powered

--
Best Regards
Tianyu Lan
linux kernel enabling team
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