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Fedora 25 - Regression with kernel 4.10 reading from a USB card reader?

asked 2017-04-23 19:35:23 -0500

updated 2017-04-23 21:47:31 -0500

hdparm -tT /dev/sdc1

kernel-4.10.10-200.fc25.x86_64

Timing buffered disk reads: 4 MB in 4.30 seconds = 953.59 kB/sec

Timing cached reads: 2 MB in 2.16 seconds = 949.72 kB/sec

kernel-4.9.14-200.fc25.x86_64

Timing buffered disk reads: 56 MB in 3.10 seconds = 18.04 MB/sec

Timing cached reads: 6538 MB in 2.00 seconds = 3270.49 MB/sec

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answered 2017-04-25 19:02:12 -0500

The reason for the slow reads on kernel 4.10.x is that the card-reader is detected as USB 1.x device with the ohci-pci driver. With kernel 4.9.x the card-reader is detected as a USB 2.0 device with the ehci-pci driver. The question should therefore be what is different about USB device detection in kernel 4.10.x vs 4.9.

lsusb -t

kernel-4.9.14-200.fc25.x86_64

/: Bus 07.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/2p, 12M

/: Bus 06.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/6p, 480M

/: Bus 01.Port 1: Dev 1, Class=roothub, Driver=ehci-pci/6p, 480M |_ Port 6: Dev 4, If 0, Class=Mass Storage, Driver=usb-storage, 480M

4.10.10-200.fc25.x86_64

/: Bus 07.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/2p, 12M

/: Bus 06.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 04.Port 1: Dev 1, Class=roothub, Driver=ohci-pci/3p, 12M |_ Port 3: Dev 3, If 0, Class=Mass Storage, Driver=usb-storage, 12M

/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M

/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/6p, 480M

/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/6p, 480M

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Asked: 2017-04-23 19:35:23 -0500

Seen: 99 times

Last updated: Apr 23 '17