Hi By performing iterative port suspend and resume (which results in function suspend and resume), ring expansion failure is observed. Attached device has multiple interfaces for which interface host drivers are unlinking the urbs during function suspend and submitting urbs during resume. For the cases when dequeue ptr is close to the end of deq segment, value of num_trbs_in_deq_seg (= ring->dequeue - ring->deq_seg->trbs) becomes high when function suspend is over. At the time of resume this high value is causing to trigger ring expansion in the middle of submitting urbs(ring->num_trbs_free < num_trbs + num_trbs_in_deq_seg). All the interface host drivers only request one TRB per urb (num_trb =1). Ring expansion logic is doubling the num of previously allocated segments every time. This is causing the num of segments to grow at fast pace (at the time of failure, one of the ep rings num_seg was 128), even though it is also increasing num_trbs_free. Even for the cases where we observe data transfer as well as suspend & resume (which are normal scenarios) ring expansion failure is easily observed due to large number of segments being allocated for ever. This means triggering of ring expansion will result in failure of further expansion at some point of time. I was trying to think of some options to reduce ring expansion with respect to suspend resume scenario: - 1) Can we reset enq and deq ptr to point to ep_ring first seg once all the urbs are unlinked (function suspend)? 2) Can we free the segments at the time of suspend and allocate segments back when resume happens? In general, as per the spec can we also implement shrinking of transfer ring (4.9.2.4). Please help to provide your comments on the options above (which can easily fit in to the current design) also feel free to add better options to consider to avoid ring expansion failures which can be added easily to the current implementation. Currently I am using 3.10 kernel and back ported recent fixes on xhci. Thanks, Hemant -- 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
