Re: [PATCH v3] usb: xhci: Add support for URB_ZERO_PACKET to bulk/sg transfers

[Reyad Attiyat]

This version of the patch changes last_trb varible name to
last_trb_num and fixes code style. I have also added a td to the urb
td array. This now gets prepared properl,y with prepare_transfer(),
and is handled correctly when transferred and completed. It only calls
the urb completion callback once as there is a check in finish_td() to
ensure that all td's have been received.

If you think I should change anything else please let me know.

Thank you,
Reyad Attiyat

On Thu, Jul 2, 2015 at 1:54 PM, Reyad Attiyat <reyad.attiyat@xxxxxxxxx> wrote:
> This commit checks for the URB_ZERO_PACKET flag and creates an extra
> zero-length td if the urb transfer length is a multiple of the endpoint's
> max packet length.
>
> Signed-off-by: Reyad Attiyat <reyad.attiyat@xxxxxxxxx>
> ---
>  drivers/usb/host/xhci-ring.c | 66 ++++++++++++++++++++++++++++++++++----------
>  drivers/usb/host/xhci.c      |  5 ++++
>  2 files changed, 57 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 7d34cbf..31ea1b9 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -3038,9 +3038,11 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>         struct xhci_td *td;
>         struct scatterlist *sg;
>         int num_sgs;
> -       int trb_buff_len, this_sg_len, running_total;
> +       int trb_buff_len, this_sg_len, running_total, ret;
>         unsigned int total_packet_count;
> +       bool zero_length_needed;
>         bool first_trb;
> +       int last_trb_num;
>         u64 addr;
>         bool more_trbs_coming;
>
> @@ -3056,13 +3058,27 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>         total_packet_count = DIV_ROUND_UP(urb->transfer_buffer_length,
>                         usb_endpoint_maxp(&urb->ep->desc));
>
> -       trb_buff_len = prepare_transfer(xhci, xhci->devs[slot_id],
> +       ret = prepare_transfer(xhci, xhci->devs[slot_id],
>                         ep_index, urb->stream_id,
>                         num_trbs, urb, 0, mem_flags);
> -       if (trb_buff_len < 0)
> -               return trb_buff_len;
> +       if (ret < 0)
> +               return ret;
>
>         urb_priv = urb->hcpriv;
> +
> +       /* Deal with URB_ZERO_PACKET - need one more td/trb */
> +       zero_length_needed = urb->transfer_flags & URB_ZERO_PACKET &&
> +               urb_priv->length == 2;
> +       if (zero_length_needed) {
> +               num_trbs++;
> +               xhci_dbg(xhci, "Creating zero length td.\n");
> +               ret = prepare_transfer(xhci, xhci->devs[slot_id],
> +                               ep_index, urb->stream_id,
> +                               1, urb, 1, mem_flags);
> +               if (ret < 0)
> +                       return ret;
> +       }
> +
>         td = urb_priv->td[0];
>
>         /*
> @@ -3092,6 +3108,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 trb_buff_len = urb->transfer_buffer_length;
>
>         first_trb = true;
> +       last_trb_num = zero_length_needed ? 2 : 1;
>         /* Queue the first TRB, even if it's zero-length */
>         do {
>                 u32 field = 0;
> @@ -3109,12 +3126,15 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 /* Chain all the TRBs together; clear the chain bit in the last
>                  * TRB to indicate it's the last TRB in the chain.
>                  */
> -               if (num_trbs > 1) {
> +               if (num_trbs > last_trb_num) {
>                         field |= TRB_CHAIN;
> -               } else {
> -                       /* FIXME - add check for ZERO_PACKET flag before this */
> +               } else if (num_trbs == last_trb_num) {
>                         td->last_trb = ep_ring->enqueue;
>                         field |= TRB_IOC;
> +               } else if (zero_length_needed && num_trbs == 1) {
> +                       trb_buff_len = 0;
> +                       urb_priv->td[1]->last_trb = ep_ring->enqueue;
> +                       field |= TRB_IOC;
>                 }
>
>                 /* Only set interrupt on short packet for IN endpoints */
> @@ -3176,7 +3196,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 if (running_total + trb_buff_len > urb->transfer_buffer_length)
>                         trb_buff_len =
>                                 urb->transfer_buffer_length - running_total;
> -       } while (running_total < urb->transfer_buffer_length);
> +       } while (num_trbs > 0);
>
>         check_trb_math(urb, num_trbs, running_total);
>         giveback_first_trb(xhci, slot_id, ep_index, urb->stream_id,
> @@ -3194,7 +3214,9 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>         int num_trbs;
>         struct xhci_generic_trb *start_trb;
>         bool first_trb;
> +       int last_trb_num;
>         bool more_trbs_coming;
> +       bool zero_length_needed;
>         int start_cycle;
>         u32 field, length_field;
>
> @@ -3225,7 +3247,6 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 num_trbs++;
>                 running_total += TRB_MAX_BUFF_SIZE;
>         }
> -       /* FIXME: this doesn't deal with URB_ZERO_PACKET - need one more */
>
>         ret = prepare_transfer(xhci, xhci->devs[slot_id],
>                         ep_index, urb->stream_id,
> @@ -3234,6 +3255,20 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 return ret;
>
>         urb_priv = urb->hcpriv;
> +
> +       /* Deal with URB_ZERO_PACKET - need one more td/trb */
> +       zero_length_needed = urb->transfer_flags & URB_ZERO_PACKET &&
> +               urb_priv->length == 2;
> +       if (zero_length_needed) {
> +               num_trbs++;
> +               xhci_dbg(xhci, "Creating zero length td.\n");
> +               ret = prepare_transfer(xhci, xhci->devs[slot_id],
> +                               ep_index, urb->stream_id,
> +                               1, urb, 1, mem_flags);
> +               if (ret < 0)
> +                       return ret;
> +       }
> +
>         td = urb_priv->td[0];
>
>         /*
> @@ -3255,7 +3290,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 trb_buff_len = urb->transfer_buffer_length;
>
>         first_trb = true;
> -
> +       last_trb_num = zero_length_needed ? 2 : 1;
>         /* Queue the first TRB, even if it's zero-length */
>         do {
>                 u32 remainder = 0;
> @@ -3272,12 +3307,15 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 /* Chain all the TRBs together; clear the chain bit in the last
>                  * TRB to indicate it's the last TRB in the chain.
>                  */
> -               if (num_trbs > 1) {
> +               if (num_trbs > last_trb_num) {
>                         field |= TRB_CHAIN;
> -               } else {
> -                       /* FIXME - add check for ZERO_PACKET flag before this */
> +               } else if (num_trbs == last_trb_num) {
>                         td->last_trb = ep_ring->enqueue;
>                         field |= TRB_IOC;
> +               } else if (zero_length_needed && num_trbs == 1) {
> +                       trb_buff_len = 0;
> +                       urb_priv->td[1]->last_trb = ep_ring->enqueue;
> +                       field |= TRB_IOC;
>                 }
>
>                 /* Only set interrupt on short packet for IN endpoints */
> @@ -3315,7 +3353,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
>                 trb_buff_len = urb->transfer_buffer_length - running_total;
>                 if (trb_buff_len > TRB_MAX_BUFF_SIZE)
>                         trb_buff_len = TRB_MAX_BUFF_SIZE;
> -       } while (running_total < urb->transfer_buffer_length);
> +       } while (num_trbs > 0);
>
>         check_trb_math(urb, num_trbs, running_total);
>         giveback_first_trb(xhci, slot_id, ep_index, urb->stream_id,
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 36bf089..40f433d 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -1340,6 +1340,11 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
>
>         if (usb_endpoint_xfer_isoc(&urb->ep->desc))
>                 size = urb->number_of_packets;
> +       else if (usb_endpoint_is_bulk_out(&urb->ep->desc) &&
> +           urb->transfer_buffer_length > 0 &&
> +           urb->transfer_flags & URB_ZERO_PACKET &&
> +           !(urb->transfer_buffer_length % usb_endpoint_maxp(&urb->ep->desc)))
> +               size = 2;
>         else
>                 size = 1;
>
> --
> 2.4.3
>
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