Re: [PATCH v5 03/21] usb: dwc2: host: Set host_rx_fifo_size to 528 for rk3066

[Doug Anderson]

Kever,

On Wed, Jan 27, 2016 at 2:13 AM, Kever Yang <kever.yang@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>

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