Re: [RESENDING RFC PATCH 1/4] dt-bindings: usb: Add snps,consolidate-sgl & consolidate-sgl

[Tejas Joglekar]

Hi,
On 4/5/2020 7:15 AM, Rob Herring wrote:
> On Fri, Mar 27, 2020 at 03:11:56PM +0530, Tejas Joglekar wrote:
>> This commit adds the documentation for consolidate-sgl, and
>> snps,consolidate-sgl property. These when set enables the quirk for
>> XHCI driver for consolidation of sg list into a temporary buffer when small
>> buffer sizes are scattered over the sg list not making up to MPS or total
>> transfer size within TRB cache size with Synopsys xHC.
>>
>> Signed-off-by: Tejas Joglekar <joglekar@xxxxxxxxxxxx>
>> ---
>>  Documentation/devicetree/bindings/usb/dwc3.txt     | 3 +++
>>  Documentation/devicetree/bindings/usb/usb-xhci.txt | 3 +++
>>  2 files changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>> index 9946ff9ba735..292d1f7969e4 100644
>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>> @@ -104,6 +104,9 @@ Optional properties:
>>  			this and tx-thr-num-pkt-prd to a valid, non-zero value
>>  			1-16 (DWC_usb31 programming guide section 1.2.3) to
>>  			enable periodic ESS TX threshold.
>> + - snps,consolidate-sgl: enable sg list consolidation - host mode only. Set to use
>> +			SG buffers of at least MPS size by consolidating smaller SG
>> +			buffers list into a single buffer.
> 
> The preference is not to keep adding properties for every single quirk 
> or feature. These should be implied by specific compatibles. As Synopsys 
> knows what quirks/errata/features are in each version of IP, the 
> compatible strings should reflect those versions. (And yes, I'm sure 
> there's customer ECO fixes that aren't reflected in the version, but 
> that's why we have SoC specific compatibles too.) This is the only way 
> we can fix quirks in the OS without doing DT updates. For comparison, do 
> you want to have to update your PC BIOS so an OS can work-around issues?
>
Yes, I understand what you want to say here. But I think this compatible string
does not work with the platform drivers with PCI based systems. So based on the vendor 
id and device id then I need to set the quirk required. 

@Felipe: What do you suggest for setting up quirk without the DT update for dwc3?
 
> Rob
> 

Thanks & Regards,
 Tejas Joglekar