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[184.205.0.249]) by smtp.gmail.com with ESMTPSA id n16sm2605492otk.25.2019.12.19.14.17.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Dec 2019 14:17:07 -0800 (PST) Date: Thu, 19 Dec 2019 16:17:04 -0600 From: Rob Herring To: Felipe Balbi Cc: Thinh Nguyen , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , "devicetree@vger.kernel.org" , Mark Rutland , John Youn Subject: Re: [RFC PATCH 13/14] usb: devicetree: dwc3: Add property to disable mult TRB fetch Message-ID: <20191219221704.GA29965@bogus> References: <87mubyvtuh.fsf@kernel.org> <6193f738-03ac-51b5-cdf0-d9b252a50146@synopsys.com> <87d0cswvs9.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87d0cswvs9.fsf@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri, Dec 13, 2019 at 09:04:54AM +0200, Felipe Balbi wrote: > > Hi, > > Thinh Nguyen writes: > >> Thinh Nguyen 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 > >>> --- > >>> 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. Well, anything would be better than the endless stream of new properties. Include 'test-mode' in the property names would be fine I guess. However, why do they need to be in DT rather than module params or debugfs settings? Changing at runtime or reloading the module is a better experience than editting a DT and rebooting. Rob