linux-kernel - Re: [PATCH v5 03/21] usb: dwc2: host: Set host_rx_fifo

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Date:	Wed, 27 Jan 2016 11:44:26 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Kever Yang <kever.yang@...k-chips.com>
Cc:	John Youn <John.Youn@...opsys.com>, Felipe Balbi <balbi@...com>,
	吴良峰 <william.wu@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Julius Werner <jwerner@...omium.org>,
	"Herrero, Gregory" <gregory.herrero@...el.com>,
	"Kaukab, Yousaf" <yousaf.kaukab@...el.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Ming Lei <ming.lei@...onical.com>,
	John Youn <johnyoun@...opsys.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 03/21] usb: dwc2: host: Set host_rx_fifo_size to 528
 for rk3066

Kever,

On Wed, Jan 27, 2016 at 2:13 AM, Kever Yang <kever.yang@...k-chips.com> wrote:
> Hi Doug,
>
> On 01/23/2016 02:18 AM, Douglas Anderson wrote:
>>
>> As documented in dwc2_calculate_dynamic_fifo(), host_rx_fifo_size should
>> really be:
>>   2 * ((Largest Packet size / 4) + 1 + 1) + n
>>   with n = number of host channel.
>>
>> We have 9 host channels, so
>>   2 * ((1024/4) + 2) + 9 = 516 + 9 = 525
>>
>> We've got 960 / 972 total_fifo_size on rk3288 (and presumably on
>> rk3066) and 525 + 128 + 256 = 909 so we're still under on both ports
>> even when we increment by 5.
>>
>> Since we have space, Kever Yang suggests bumping by 8.  He says this
>> will meet INCR16 access and next fifo type can start with a aligned
>> address.
>
> I have double check this feature, the INCR16 is actually a burst 16
> on to the bus, the aligned problem only happen on the DRAM
> access, and it's OK for internal RAM access via internal DMA.
>
> Bump to 8 looks much better when we check the FIFO setting if we
> have enough memory, right? :)
>
> rk3066/rk3188/rk3288 have the same hw config for dwc2 controller,
> so this patch should works on those files.
>
> Reviewed-by: Kever Yang <kever.yang@...k-chips.com>

Thanks for double-checking and thanks for the review!

If it's all the same to you, I'll probably change it back to 525 and
then increase the periodic FIFO size by 3 DWORDS in the next patch.
12 bytes may not be much, but might as well make use of them to
improve performance / compatibility?

Presumably you're also OK with the next patch in the series: ("usb:
dwc2: host: Set host_perio_tx_fifo_size to 304 for rk3066")?

Note to anyone who may be thinking of applying patches in this series:

* You can skip both this and the next patch if you wish and any other
patches in the series are unaffected.

* You can request that I spin just these two patches and I will do it
ASAP.  Otherwise I'll add that fix to the next spin of the whole
series.

* You can make the changes yourself to this patch and the next one
(this patch should be 525 and the next should increase
host_perio_tx_fifo_size to 307).

I'm OK with any of those 3 things.  ;)

-Doug