Re: [PATCH 0/3] dwc2: Speed up the interrupt handler quite a bit

From: Heiko Stuebner
Date: Thu Nov 05 2015 - 14:19:52 EST

Am Mittwoch, 4. November 2015, 14:53:02 schrieb Douglas Anderson:
> The dwc2 interrupt handler is quite slow. On rk3288 with a few things
> plugged into the ports and with cpufreq locked at 696MHz (to simulate
> real world idle system), I can easily observe dwc2_handle_hcd_intr()
> taking > 120 us, sometimes > 150 us. Note that SOF interrupts come
> every 125 us with high speed USB, so taking > 120 us in the interrupt
> handler is a big deal.
> The patches here will speed up the interrupt controller significantly.
> After this series, I have a hard time seeing the interrupt controller
> taking > 20 us and I don't ever see it taking > 30 us ever in my tests
> unless I bring the cpufreq back down. With the cpufreq at 126 MHz I can
> still see the interrupt handler take > 50 us, so I'm sure we could
> improve this further. ...but hey, it's a start.
> In addition to the speedup, this series also has the advantage of
> simplifying dwc2 and making it more like everyone else (introducing the
> possibility of future simplifications). Picking this series up will
> help your diffstat and likely win you friends. ;)

I gave this a simple spin on my veyron-pinky with both a device attached
directly to the port as well as with an usb-hub in between. Everything was
still working smoothly, so

Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>
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