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

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Date:	Fri, 30 Oct 2015 16:08:26 +0800
From:	Liangfeng Wu <wulf@...k-chips.com>
To:	Douglas Anderson <dianders@...omium.org>,
	John Youn <John.Youn@...opsys.com>, balbi@...com
CC:	Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	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

On 10/21/2015 07:33 AM, Douglas Anderson wrote:
> 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>
> ---
>   drivers/usb/dwc2/platform.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
> index 5859b0f..e61d773 100644
> --- a/drivers/usb/dwc2/platform.c
> +++ b/drivers/usb/dwc2/platform.c
> @@ -108,7 +108,8 @@ static const struct dwc2_core_params params_rk3066 = {
>   	.host_ls_low_power_phy_clk	= -1,
>   	.ts_dline			= -1,
>   	.reload_ctl			= -1,
> -	.ahbcfg				= 0x7, /* INCR16 */
> +	.ahbcfg				= GAHBCFG_HBSTLEN_INCR16 <<
> +					  GAHBCFG_HBSTLEN_SHIFT,
>   	.uframe_sched			= -1,
>   	.external_id_pin_ctl		= -1,
>   	.hibernation			= -1,

Reviewed-by:  Liangfeng Wu <wulf@...k-chips.com>

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