From e6abdf5a6f8f5ac57c8dae509cb5b0d320ea906b Mon Sep 17 00:00:00 2001 From: Dongwoo Lee Date: Mon, 7 Nov 2016 14:34:15 +0900 Subject: [PATCH] usb: xhci: Limit transfer length of a single TD This is workaround solution for timed out error and babble error while transfering data exceeding 0x3F01FF bytes on xhci host. Actually, this size equals to value that the maximum number of TRBs per TD times the maximum size of transfer buffer on TRB. Thus, huge transfer request is splitted in order to limit the size of data in a single TD. Even though the single I/O request is splitted into multiple requests, the transfer speed has affected insignificantly: 22.6 --> 22.3 MiB/s. Change-Id: I85a17910587b70807f075dd40634a0da817cea2f Signed-off-by: Dongwoo Lee --- drivers/usb/host/xhci.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index 126dabc11b..0b95efcb1b 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -1183,12 +1183,40 @@ static int _xhci_submit_int_msg(struct usb_device *udev, unsigned long pipe, static int _xhci_submit_bulk_msg(struct usb_device *udev, unsigned long pipe, void *buffer, int length) { + int ret; + int xfer_max_per_td, xfer_length, buf_pos; + if (usb_pipetype(pipe) != PIPE_BULK) { printf("non-bulk pipe (type=%lu)", usb_pipetype(pipe)); return -EINVAL; } - return xhci_bulk_tx(udev, pipe, length, buffer); + /* + * When transfering data exceeding the maximum number of TRBs per + * TD (default 64) is requested, the transfer fails with babble + * error or time out. + * + * Thus, huge data transfer should be splitted into multiple TDs. + */ + xfer_max_per_td = TRB_MAX_BUFF_SIZE * (TRBS_PER_SEGMENT - 1); + + buf_pos = 0; + do { + if (length > xfer_max_per_td) + xfer_length = xfer_max_per_td; + else + xfer_length = length; + + ret = xhci_bulk_tx(udev, pipe, xfer_length, buffer + buf_pos); + if (ret < 0) + return ret; + + buf_pos += xfer_length; + length -= xfer_length; + + } while (length > 0); + + return ret; } /** -- 2.34.1