On Tue, Mar 20, 2018 at 03:34:16PM +0200, Felipe Balbi wrote: > > Hi, > > Bin Liu <b-liu@xxxxxx> writes: > >> >> > > BTY, the issue I am trying to debug is when reading bulk IN data from a > >> >> > > USB2.0 device, if the device doesn't have data to transmit and NAKs the > >> >> > > IN packet, after 4 pairs of IN-NAK transactions, xhci stops sending > >> >> > > further IN tokens until the next SOF, which leaves ~90us gape on the > >> >> > > bus. > >> >> > > > >> >> > > But when reading data from a USB2.0 thumb drive, this issue doesn't > >> >> > > happen, even if the device NAKs the IN tokens, xhci still keeps sending > >> >> > > IN tokens, which is way more than 4 pairs of IN-NAK transactions. > >> >> > > >> >> > Thumb drive has Bulk endpoints, what is the other device's transfer type? > >> >> > >> >> It is bulk too. I asked for device descriptors. This is a remote debug > >> >> effort for me, I don't have that device... > >> >> > >> >> > > >> >> > > Any one has a clue on what causes xhci to stop sending IN tokens after > >> >> > > the device NAK'd 4 times? > >> > > >> > By accident, I reproduced the issue if addng a hub in the middle... > >> > any comments about why a hub changes this xhci behavior is appreciated. > >> > >> none off the top of my head. Maybe Mathias can suggest something. > > > > The issue seems to be not related to how many bulk IN-NAK pairs before > > host stops sending IN token, but the host stops IN token if 1) the > > device ever NAK'd an bulk IN token, and 2) there is about 90~100us left > > to the next SOF. Then all the rest of bandwidth is wasted. > > > > Is it about xhci bandwidth schduling? /me started reading... > > is this AM4 or AM5? Perhaps go after Synopsys' known errata list? I see the issue on both AM4 & AM5. I don't have access to the errata list, I guess I should talk to TI internal for the list? Regards, -Bin. -- 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
