Re: [RFC PATCH 13/14] usb: devicetree: dwc3: Add property to disable mult TRB fetch

[Felipe Balbi <balbi@kernel.org>]

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Hi,

Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:
>> Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:
>>> DWC_usb32 has a feature where it can issue multiple TRB fetch requests.
>>> Add a new property to limit and only do only single TRB fetch request.
>>>
>>> Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
>>> ---
>>>   Documentation/devicetree/bindings/usb/dwc3.txt | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>>> index ff35fa6de2eb..29d6f9b1fc70 100644
>>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>>> @@ -108,6 +108,8 @@ Optional properties:
>>>    - snps,num-trb-prefetch: max value to do TRBs cache for DWC_usb32. The value
>>>   			can be from 1 to DWC_USB32_CACHE_TRBS_PER_TRANSFER.
>>>   			Default value is DWC_USB32_CACHE_TRBS_PER_TRANSFER.
>>> + - snps,dis-mult-trb-fetch: set to issue only single TRB fetch request in
>>> +			DWC_usb32.
>> two questions:
>>
>> - how is this different from passing 1 to the previous DT binding
>
> The previous DT binding is related to the number TRBs to cache while 
> this one is related to whether the controller will send multiple 
> (internal) fetch commands to fetch the TRBs.
>
>> - do we know of anybody having issues with multi-trb prefetch?
>
> No, we added this for various internal tests.

We really a better way for you guys to have your test coverage enabled
with upstream kernel. I wonder if DT guys would accept a set of bindings
marked as "for testing purposes". In any case, we really need to enable
Silicon Validation with upstream kernel.

-- 
balbi

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