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

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Hi,

Felipe Balbi wrote:
> Hi,
>
> Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> writes:
>>> Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
>>>> ---
>>>>    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.
>

That would be great! If there's a sensible way to do so, we're open to 
suggestions.

Thanks,
Thinh




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