netdev - Re: [PATCH v4 4/4] can: kvaser_usb: Retry first bulk transfer on -ETIMEDOUT

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Message-ID: <20150112101407.GA9213@linux>
Date:	Mon, 12 Jan 2015 05:14:07 -0500
From:	"Ahmed S. Darwish" <darwish.07@...il.com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>
Cc:	Olivier Sobrie <olivier@...rie.be>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux-USB <linux-usb@...r.kernel.org>,
	Linux-CAN <linux-can@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] can: kvaser_usb: Retry first bulk transfer on
 -ETIMEDOUT

On Sun, Jan 11, 2015 at 09:51:10PM +0100, Marc Kleine-Budde wrote:
> On 01/11/2015 09:45 PM, Ahmed S. Darwish wrote:
> > From: Ahmed S. Darwish <ahmed.darwish@...eo.com>
> > 
> > (This is a draft patch, I'm not sure if this fixes the USB
> > bug or only its psymptom. Feedback from the linux-usb folks
> > is really appreciated.)
> > 
> > When plugging the Kvaser USB/CAN dongle the first time, everything
> > works as expected and all of the transfers from and to the USB
> > device succeeds.
> > 
> > Meanwhile, after unplugging the device and plugging it again, the
> > first bulk transfer _always_ returns an -ETIMEDOUT. The following
> > behaviour was observied:
> > 
> > - Setting higher timeout values for the first bulk transfer never
> >   solved the issue.
> > 
> > - Unloading, then loading, our kvaser_usb module in question
> >   __always__ solved the issue.
> > 
> > - Checking first bulk transfer status, and retry the transfer
> >   again in case of an -ETIMEDOUT also __always__ solved the issue.
> >   This is what the patch below does.
> > 
> > - In the testing done so far, this issue appears only on laptops
> >   but never on PCs (possibly power related?)
> > 
> > Signed-off-by: Ahmed S. Darwish <ahmed.darwish@...eo.com>
> 
> Does this patch apply apply between 3 and 4? If not, please re-arrange
> the series. As this is a bug fix, patches 1, 2 and 4 will go via
> net/master, 3 will go via net-next/master.
> 

Since no one complained earlier, I guess this issue only affects
USBCAN devices. That's why I've based it above patch #3: adding
USBCAN hardware support.

Nonetheless, it won't do any harm for the current Leaf-only
driver. So _if_ this is the correct fix, I will update the commit
log, refactor the check into a 'do { } while()' loop, and then
base it above the Leaf-only net/master fixes on patch #1, and #2.

Any feedback on the USB side of things?

Thanks,
Darwish
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