Hi, Bin Liu <b-...@ti.com> writes: >> Bin Liu <b-...@ti.com> 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?
Right, your HW folks should have a pointer. Dave K may be a good starting contact ;-) -- balbi
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