Since you both seem to be asking the same question: On Wed, Oct 17, 2012 at 10:34:39AM +0530, ankit patel wrote: > Thanks Sarah, > I just need to know that driver is doing reset when device is not > attached by writing HCRST to 1 in USB Command Register of xHC. Does > the host controller needs to propagate HOT/WARM reset to USB3 layer when > device is not attached ? If yes then when should we consider it to be > complete? Steve McGowan, the xHCI spec architect, is on sabbatical. He'll be back on Oct 30, and I'm sure he'll answer your questions then. Until that point, I suggest you fix your host controller bug for when the host gives a TRB pointer for the TRB *after* the TD that finished. On Wed, Oct 17, 2012 at 03:06:48PM +0530, Chintan Mehta wrote: > Hi Sarah, > > I have got your mail ID from http://gmane.org during my search regarding > USB3 xHCI Driver. > > We have some doubts about xHCI Host Spec. > > We tried to contact on xhcisupport@xxxxxxxxx, but we have not received any > reply yet. > > Can you please, help us to resolve our queries? > > One more question: > xHCI Driver seems to be doing HCRST on startup. > If device is not connected, xHCI should propagate Hot/Warm reset to USB3 > layer? I don't know. Ask Steve. More comments below. > On Fri, Sep 28, 2012 at 4:49 PM, Chintan Mehta < > chintan.mehta@xxxxxxxxxxxxxxxx> wrote: > > > Hi, > > > > We have some queries regarding TDSize in different TRBs. > > > > 1. In setup-data-status control transfer case: > > > > - Device is informed about the transfer length of data stage through > > wLength filed in setup stage. You should not rely on the transfer length in the setup stage. Section 4.11.2.2 says, "Note: Some (non-compliant) USB devices use the SETUP Data wLength field as a custom parameter for non-data control transfers. xHCI implementations should not tie a non-zero wLength value to the existence of a Data Stage TD in a control transfer to ensure compatibility with those devices." Don't use the setup stage. Instead, fetch the first data stage TRB, and use the TD size field. > > - Now, data stage may contain data stage trb followed by chained > > normal trbs to complete the data stage transfer. > > - Question is as below: > > - *Chained normal TRB should be placed only when the total data > > transfer is more than maxpacket size or data transfer can be broken into > > different TRBs?* Data transfers can be broken down into any number of TRBs. There is no requirement that they are broken into maxpacket sized chunks. Each TRB could have more or less bytes than maxpacket size. Your host will have to deal with both. > > - *If chained normal TRB can be placed without considering the > > maxpacket size rule, what should be the value of TDSize in data stage TRB? The number of bytes remaining in the TD, *including* this TRB. So TDSize will decrease on each TRB in the TD. (Or stay the same for several TDs, if this TD is bigger than what can be represented in the TD size field). > > * > > - To elaborate above question, If 9 Bytes are requested in setup > > stage. Driver may either put data stage trb with TRB transfer length 9 > > Bytes or may put a chained normal trb after data stage trb. Don't rely on the setup stage wLength. > > - Lets say driver is breaking transfer in two stages and puts data > > stage trb with TRB transfer length 8 Bytes, chain bit 1 and TDSize 0 - > > followed by Normal trb with TRB transfer size 1 Byte, Chain bit 0 and > > TDSize 0. > > - *Is this breaking is proper/valid from driver side?* See section 4.11.2.4. TD size is the number of bytes remaining, right shifted by 10. (8 >> 10) = 0. (1 >> 10) = 0. The TD size is just an estimation of the number of bytes remaining. You'll have to look at the chain bit to know whether you need to fetch more data for this TD. > > 2. For Bulk Endpoint: > > > > - *Driver can put a TD with total TD transfer size less than maxpacket > > size and more than 1 TRB?* > > - For example, Maxpacketsize is 1K. And TD contains 3 TRBs as below: > > - 1st trb with TRB transfer length 600 Bytes, chain bit 1 and > > TDSize 0 > > - 2nd trb with TRB transfer length 200 Bytes, chain bit 1 and > > TDSize 0 > > - 3rd trb with TRB transfer length 100 Bytes, chain bit 0 and > > TDSize 0 > > - *What should be the value of TDSize in above TRBs of TD?* Again, see section 4.11.2.4. TRB 1 600 (600 + 200 + 100) >> 10 = 0 TRB 2 200 (200 + 100) >> 10 = 0 TRB 3 100 (100) >> 10 = 0 Let me know if Steve disagrees. The xHCI driver works with many other host controllers, and that's how it implements TD size. Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
