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:
>> 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.

BR,
Thinh




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