On Mon, Jul 21, 2014 at 05:28:58PM +0200, Laurent Pinchart wrote:
> Hi Adam,
>
> On Wednesday 29 January 2014 08:44:57 Adam Wozniak wrote:
> > With a USB 2.0 webcam attached to the OTG port on an OMAP3 (applies to
> > overo gumstix, beagleboard, probably others) we see a high CPU load in a
> > kworker thread.
> >
> > Between 2.6.33 and 2.6.34 musb_core.c changed.
> >
> > IRQ handlers changed with the result that a worker in musb_core.c got
> > scheduled far more frequently than needed.
> >
> > I've included a patch below against 3.7, but i think it'll apply against
> > mainline.
> > [I apologize for any whitespace mangling. I've also attached the patch.]
> >
> > I'd like more eyeballs to tell me if this is right. I'd also like to
> > know who I need to talk to to get this pushed into mainline.
>
> Running the scripts/get_maintainer.pl script on your patch produces
>
> Felipe Balbi <balbi@xxxxxx> (maintainer:MUSB MULTIPOINT H...)
> Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> (supporter:USB SUBSYSTEM)
> linux-usb@xxxxxxxxxxxxxxx (open list:MUSB MULTIPOINT H...)
> linux-kernel@xxxxxxxxxxxxxxx (open list)
>
> Felipe Balbi (CC'ed) is the person who you should talk to.
>
> While we're touching the subject of scripts, you should run the
> scripts/checkpatch.pl script and fix errors and warnings before submitting
> patches. Please see Documentation/SubmittingPatches.
>
> Last (but not least) piece of advice, don't give up if you don't receive
> replies to your patches. People are busy and mails fall to cracks from time to
> time.
>
> Felipe, apart from the coding style violation and the possibly missing
> locking, what's your opinion on this ? Does the patch make sense ?
It's a duplication of the check which is already in musb_irq_work():
1742 static void musb_irq_work(struct work_struct *data)
1743 {
1744 struct musb *musb = container_of(data, struct musb, irq_work);
1745
1746 if (musb->xceiv->state != musb->xceiv_old_state) {
1747 musb->xceiv_old_state = musb->xceiv->state;
1748 sysfs_notify(&musb->controller->kobj, NULL, "mode");
1749 }
1750 }
That does look better, but I'd need the check inside musb_irq_work() to
be removed and commit log would have to improve a bit.
ps: there's no missing locking, musb_stage0_irq() is called within
musb_interrupt() which is called within a locked IRQ handler.
--
balbi
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