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

From: Liangfeng Wu <wulf@rock-chips.com>
To: Douglas Anderson <dianders@chromium.org>,
	John Youn <John.Youn@synopsys.com>,
	balbi@ti.com
Cc: "Yunzhi Li" <lyz@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	linux-rockchip@lists.infradead.org,
	"Julius Werner" <jwerner@chromium.org>,
	johnyoun@synopsys.com, gregkh@linuxfoundation.org,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: dwc2: host: Fix ahbcfg for rk3066
Date: Fri, 30 Oct 2015 16:08:26 +0800	[thread overview]
Message-ID: <5633257A.5020306@rock-chips.com> (raw)
In-Reply-To: <1445384033-17050-1-git-send-email-dianders@chromium.org>

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@chromium.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@rock-chips.com>