From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kishon Vijay Abraham I Date: Mon, 2 Mar 2015 19:34:59 +0530 Subject: [U-Boot] DWC2 driver issues In-Reply-To: <201503021238.53699.marex@denx.de> References: <54E236DD.3080204@wwwdotorg.org> <201502191529.02337.marex@denx.de> <54E6A892.9040304@wwwdotorg.org> <201503021238.53699.marex@denx.de> Message-ID: <54F46E0B.8050309@ti.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Monday 02 March 2015 05:08 PM, Marek Vasut wrote: > On Friday, February 20, 2015 at 04:22:58 AM, Stephen Warren wrote: > > Hi! > > [...] > >>>> Existing code that invokes USB transfers will call (a) once. (a) will >>>> call (b) as many times as needed to break up the packet into small >>>> chunks. (b) will either send the transaction to the HW (HS devices or >>>> directly attached LS/FS devices), or perform the split transaction >>>> handling (remotely attached LS/FS devices). >>>> >>>> Does that sound like a reasonable approach? >>>> >>>> I can start looking into getting split transactions going; I just >>>> couldn't motivate myself last Friday night. >>> >>> Do you plan to do this on the USB stack level or USB controller driver >>> level please ? >> >> I expect I'd put at least the split transaction stuff into the USB >> controller driver. While I'm not that familiar with anything other than >> standard EHCI, I'd guess the need to manually manage split transaction >> was unique to DWC2? > > Looks that way. +CC Kishon , what about DWC3 ? SPLIT transaction is specific to host controller and the DWC3 work I did is gadget driver. So I'd assume it should be handled by xhci driver. > >> The split of transfers into max-packet-sized transfers could plausibly >> be useful in the core, but again my guess is that the need to do this is >> DWC2-specific? > > Kishon ? AFAIK dwc3 requires max-packet "aligned" request sizes and we manage it by using bounce buffer and chained TRBs. The hw itself takes care of sending max-packet-sized transfers. But again I'm talking w.r.t gadget driver. Cheers Kishon