On Wed, 23 Aug 2017, David Mosberger wrote:
> Alan,
>
> On Wed, Aug 23, 2017 at 10:30 AM, Alan Stern
> wrote:
>
> >> Does anybody know why HCD_BH is not enabled in ohci-hcd.c?
> >
> > Because it changes the semantics of isochronous and interrupt
> > streaming. See for example commits 9118f9eb
On Wed, 23 Aug 2017, David Mosberger wrote:
> Actually, I just found this commit:
>
> 94dfd7edf USB: HCD: support giveback of URB in tasklet context
>
> It won't fix the problem entirely, but I think it should cut the worst-case
> irqs-disabled latency about in half, which would be a good improv
On Wed, 23 Aug 2017, David Mosberger wrote:
> On Tue, Aug 22, 2017 at 3:40 PM, Greg KH wrote:
> > On Tue, Aug 22, 2017 at 02:44:20PM -0600, David Mosberger wrote:
>
> >> > There was an option a while ago to turn USB irqs
> >> > into threaded irqs, do those work on your platform? If so, that mig
Actually, I just found this commit:
94dfd7edf USB: HCD: support giveback of URB in tasklet context
It won't fix the problem entirely, but I think it should cut the worst-case
irqs-disabled latency about in half, which would be a good improvement.
Does anybody know why HCD_BH is not enabled in oh
On Tue, Aug 22, 2017 at 3:40 PM, Greg KH wrote:
> On Tue, Aug 22, 2017 at 02:44:20PM -0600, David Mosberger wrote:
>> > There was an option a while ago to turn USB irqs
>> > into threaded irqs, do those work on your platform? If so, that might
>> > help you out here.
>>
>> Do you mean this:
>>
>
On Tue, Aug 22, 2017 at 3:40 PM, Greg KH wrote:
> On Tue, Aug 22, 2017 at 02:44:20PM -0600, David Mosberger wrote:
>> Greg,
>>
>> On Tue, Aug 22, 2017 at 2:25 PM, Greg KH wrote:
>>
>> > USB has always been a big problem with this, the IRQ patch is very long,
>> > and messy and complex.
>>
>> Yeah
On Tue, Aug 22, 2017 at 02:44:20PM -0600, David Mosberger wrote:
> Greg,
>
> On Tue, Aug 22, 2017 at 2:25 PM, Greg KH wrote:
>
> > USB has always been a big problem with this, the IRQ patch is very long,
> > and messy and complex.
>
> Yeah.
>
> > There was an option a while ago to turn USB irq
Greg,
On Tue, Aug 22, 2017 at 2:25 PM, Greg KH wrote:
> USB has always been a big problem with this, the IRQ patch is very long,
> and messy and complex.
Yeah.
> There was an option a while ago to turn USB irqs
> into threaded irqs, do those work on your platform? If so, that might
> help you
On Tue, Aug 22, 2017 at 12:42:33PM -0600, David Mosberger wrote:
> Has anyone here looked into reducing the amount of time the USB serial
> driver disables interrupts? On an ARM system, I'm seeing about 746 us
> of latency for handling a USB interrupt, which seems rather excessive.
> I attached a
Has anyone here looked into reducing the amount of time the USB serial
driver disables interrupts? On an ARM system, I'm seeing about 746 us
of latency for handling a USB interrupt, which seems rather excessive.
I attached a trace captured with the irqsoff tracer.
Note: the 500MHz ARM cycle count
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