Hi all,
I'm on USB certification of a vendor SoC, and there's a case called
"Bus powered hub power exceeded test" in the compliance plan defined
by the usb.org. It requires an error message when a device (Max power
descriptor >100mA) is attached to an external bus powered hub.
But when I attached the bus powered hub to Linux (Ubuntu 14.04), I
found that it always reported as self powered
Bus 002 Device 026: ID 1a40:0801 Terminus Technology Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 1 Single TT
bMaxPacketSize0 64
idVendor 0x1a40 Terminus Technology Inc.
idProduct 0x0801
bcdDevice 1.00
iManufacturer 0
iProduct 1 USB 2.0 Hub
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 25
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xe0
Self Powered
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 9 Hub
bInterfaceSubClass 0 Unused
bInterfaceProtocol 0 Full speed (or root) hub
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0001 1x 1 bytes
bInterval 12
Hub Descriptor:
bLength 9
bDescriptorType 41
nNbrPorts 4
wHubCharacteristic 0x0000
Ganged power switching
Ganged overcurrent protection
TT think time 8 FS bits
bPwrOn2PwrGood 50 * 2 milli seconds
bHubContrCurrent 100 milli Ampere
DeviceRemovable 0x00
PortPwrCtrlMask 0xff
Hub Port Status:
Port 1: 0000.0100 power
Port 2: 0000.0100 power
Port 3: 0000.0100 power
Port 4: 0000.0100 power
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 0 Full speed (or root) hub
bMaxPacketSize0 64
bNumConfigurations 1
Device Status: 0x0001
Self Powered
And I've checked the source code in drivers/usb/core/hub.c
1521 if (hdev == hdev->bus->root_hub) {
1522 if (hcd->power_budget > 0)
1523 hdev->bus_mA = hcd->power_budget;
1524 else
1525 hdev->bus_mA = full_load * maxchild;
1526 if (hdev->bus_mA >= full_load)
1527 hub->mA_per_port = full_load;
1528 else {
1529 hub->mA_per_port = hdev->bus_mA;
1530 hub->limited_power = 1;
1531 }
1532 } else if ((hubstatus & (1 << USB_DEVICE_SELF_POWERED))
== 0) {
1533 int remaining = hdev->bus_mA -
1534 hub->descriptor->bHubContrCurrent;
1535
1536 dev_dbg(hub_dev, "hub controller current
requirement: %dmA\n",
1537 hub->descriptor->bHubContrCurrent);
1538 hub->limited_power = 1;
1539
1540 if (remaining < maxchild * unit_load)
1541 dev_warn(hub_dev,
1542 "insufficient power
available "
1543 "to use all downstream
ports\n");
1544 hub->mA_per_port = unit_load; /* 7.2.1 */
1545
1546 } else { /* Self-powered external hub */
1547 /* FIXME: What about battery-powered external
hubs that
1548 * provide less current per port? */
1549 hub->mA_per_port = full_load;
1550 }
The hub->mA_per_port is always set as full_load (500mA for usb 2.0
hub) since reported as self powered hub.
So when I attach a usb device with ( 100mA < Max power descriptor <=
500mA), linux won't show error messages.
I'm wondering why the bus powered hub reported as self powered? And is
any switch to make it bus powered?
Thanks!
Regards
Rong
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