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

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Date:	Thu, 05 Nov 2015 20:18:56 +0100
From:	Heiko Stuebner <heiko@...ech.de>
To:	Douglas Anderson <dianders@...omium.org>
Cc:	John Youn <John.Youn@...opsys.com>, balbi@...com,
	Yunzhi Li <lyz@...k-chips.com>,
	linux-rockchip@...ts.infradead.org,
	Julius Werner <jwerner@...omium.org>,
	gregory.herrero@...el.com, yousaf.kaukab@...el.com,
	dinguyen@...nsource.altera.com, johnyoun@...opsys.com,
	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] dwc2: Speed up the interrupt handler quite a bit

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@...ech.de>
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