linux-kernel - Re: [PATCH] usb: dwc2: host: Fix ahbcfg for rk3066

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Date:	Sat, 24 Oct 2015 15:08:05 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Douglas Anderson <dianders@...omium.org>
Cc:	John Youn <John.Youn@...opsys.com>, balbi@...com,
	Wu Liang Feng <wulf@...k-chips.com>,
	Yunzhi Li <lyz@...k-chips.com>,
	linux-rockchip@...ts.infradead.org,
	Julius Werner <jwerner@...omium.org>, johnyoun@...opsys.com,
	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: dwc2: host: Fix ahbcfg for rk3066

Am Dienstag, 20. Oktober 2015, 16:33:53 schrieb Douglas Anderson:
> The comment for ahbcfg for rk3066 parameters (also used for rk3288)
> claimed that ahbcfg was INCR16, but it wasn't.  Since the bits weren't
> shifted properly, the 0x7 ended up being masked and we ended up
> programming 0x3 for the HBstLen.  Let's set it to INCR16 properly.
> 
> As per Wu Liang Feng at Rockchip this may increase transmission
> efficiency.  I did blackbox tests with writing 0s to a USB-based SD
> reader (forcefully capping CPU Freq to try to measure efficiency):
>   cd /sys/devices/system/cpu/cpu0/cpufreq
>   echo userspace > scaling_governor
>   echo 126000 > scaling_setspeed
>   for i in $(seq 10); do
>     dd if=/dev/zero of=/dev/sdb bs=1M count=750
>   done
> 
> With the above tests I found that speeds went from ~15MB/s to ~18MB/s.
> Note that most other tests I did (including reading from the same USB
> reader) didn't show any difference in performance.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

I gave this a spin on a rk3288-firefly, runs fine and doesn't have any 
negative effects, so

Tested-by: Heiko Stuebner <heiko@...ech.de>
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