port 1 disabled by hub (EMI?), re-enabling...

[Ravishankar]

On Fri, Jan 11, 2013 at 7:07 PM, Rahul Bedarkar <rpal143 at gmail.com> wrote:
> Hi,
>
> When I remove pen-drive, I am seeing following logs
>
> [  132.968942]   Disconnect Detected Interrupt++ (Host) a_host
> [  133.196692] hub 1-0:1.0: port 1 disabled by hub (EMI?), re-enabling...

So, did you  grep for the EMI thingy in the source?

> [  133.207595] usb 1-1: USB disconnect, device number 2
> [  164.420649] sd 0:0:0:0: Device offlined - not ready after error recovery
> [  164.447670] sd 0:0:0:0: [sda] Unhandled error code
> [  164.459347] sd 0:0:0:0: [sda]  Result: hostbyte=0x01 driverbyte=0x00
> [  164.482169] sd 0:0:0:0: [sda] CDB: cdb[0]=0x2a: 2a 00 00 15 65 f8 00 00
> 08 00
> [  164.643217] end_request: I/O error, dev sda, sector 1402360
>
> Why EMI is coming into picture here ?
>

I don't know *anything* about USB drivers but hey, I know how to grep
my way through.
And that is what I did:
git grep "EMI?" drivers/usb/

And look what I found in drivers/core/hub.c!

                                /*
                                 * EM interference sometimes causes badly
                                 * shielded USB devices to be shutdown by
                                 * the hub, this hack enables them again.
                                 * Works at least with mouse driver.
                                 */
Cool.So now you know how EMI came into the picture.
Moral of the story: Looking at the code can make you look less
foolish. Or perhaps make you more intelligent :)

>
> Thanks,
> Rahul B.
>
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