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authorSarah Sharp <sarah.a.sharp@linux.intel.com>2010-04-16 11:07:27 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2010-04-30 12:25:10 -0400
commit9238f25d5d32a435277eb234ec82bacdd5daed41 (patch)
tree0f2bed8916468806c0f35e3a29534d7ea8342ef3 /drivers
parent1cf62246c0e394021e494e0a8f1013e80db1a1a9 (diff)
USB: xhci: properly set endpoint context fields for periodic eps.
For periodic endpoints, we must let the xHCI hardware know the maximum payload an endpoint can transfer in one service interval. The xHCI specification refers to this as the Maximum Endpoint Service Interval Time Payload (Max ESIT Payload). This is used by the hardware for bandwidth management and scheduling of packets. For SuperSpeed endpoints, the maximum is calculated by multiplying the max packet size by the number of bursts and the number of opportunities to transfer within a service interval (the Mult field of the SuperSpeed Endpoint companion descriptor). Devices advertise this in the wBytesPerInterval field of their SuperSpeed Endpoint Companion Descriptor. For high speed devices, this is taken by multiplying the max packet size by the "number of additional transaction opportunities per microframe" (the high bits of the wMaxPacketSize field in the endpoint descriptor). For FS/LS devices, this is just the max packet size. The other thing we must set in the endpoint context is the Average TRB Length. This is supposed to be the average of the total bytes in the transfer descriptor (TD), divided by the number of transfer request blocks (TRBs) it takes to describe the TD. This gives the host controller an indication of whether the driver will be enqueuing a scatter gather list with many entries comprised of small buffers, or one contiguous buffer. It also takes into account the number of extra TRBs you need for every TD. This includes No-op TRBs and Link TRBs used to link ring segments together. Some drivers may choose to chain an Event Data TRB on the end of every TD, thus increasing the average number of TRBs per TD. The Linux xHCI driver does not use Event Data TRBs. In theory, if there was an API to allow drivers to state what their bandwidth requirements are, we could set this field accurately. For now, we set it to the same number as the Max ESIT payload. The Average TRB Length should also be set for bulk and control endpoints, but I have no idea how to guess what it should be. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/usb/host/xhci-mem.c51
-rw-r--r--drivers/usb/host/xhci.h4
2 files changed, 55 insertions, 0 deletions
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 4ed9f5f7a146..d64f5724bfc4 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -625,6 +625,36 @@ static inline u32 xhci_get_endpoint_type(struct usb_device *udev,
625 return type; 625 return type;
626} 626}
627 627
628/* Return the maximum endpoint service interval time (ESIT) payload.
629 * Basically, this is the maxpacket size, multiplied by the burst size
630 * and mult size.
631 */
632static inline u32 xhci_get_max_esit_payload(struct xhci_hcd *xhci,
633 struct usb_device *udev,
634 struct usb_host_endpoint *ep)
635{
636 int max_burst;
637 int max_packet;
638
639 /* Only applies for interrupt or isochronous endpoints */
640 if (usb_endpoint_xfer_control(&ep->desc) ||
641 usb_endpoint_xfer_bulk(&ep->desc))
642 return 0;
643
644 if (udev->speed == USB_SPEED_SUPER) {
645 if (ep->ss_ep_comp)
646 return ep->ss_ep_comp->desc.wBytesPerInterval;
647 xhci_warn(xhci, "WARN no SS endpoint companion descriptor.\n");
648 /* Assume no bursts, no multiple opportunities to send. */
649 return ep->desc.wMaxPacketSize;
650 }
651
652 max_packet = ep->desc.wMaxPacketSize & 0x3ff;
653 max_burst = (ep->desc.wMaxPacketSize & 0x1800) >> 11;
654 /* A 0 in max burst means 1 transfer per ESIT */
655 return max_packet * (max_burst + 1);
656}
657
628int xhci_endpoint_init(struct xhci_hcd *xhci, 658int xhci_endpoint_init(struct xhci_hcd *xhci,
629 struct xhci_virt_device *virt_dev, 659 struct xhci_virt_device *virt_dev,
630 struct usb_device *udev, 660 struct usb_device *udev,
@@ -636,6 +666,7 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
636 struct xhci_ring *ep_ring; 666 struct xhci_ring *ep_ring;
637 unsigned int max_packet; 667 unsigned int max_packet;
638 unsigned int max_burst; 668 unsigned int max_burst;
669 u32 max_esit_payload;
639 670
640 ep_index = xhci_get_endpoint_index(&ep->desc); 671 ep_index = xhci_get_endpoint_index(&ep->desc);
641 ep_ctx = xhci_get_ep_ctx(xhci, virt_dev->in_ctx, ep_index); 672 ep_ctx = xhci_get_ep_ctx(xhci, virt_dev->in_ctx, ep_index);
@@ -703,6 +734,26 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
703 default: 734 default:
704 BUG(); 735 BUG();
705 } 736 }
737 max_esit_payload = xhci_get_max_esit_payload(xhci, udev, ep);
738 ep_ctx->tx_info = MAX_ESIT_PAYLOAD_FOR_EP(max_esit_payload);
739
740 /*
741 * XXX no idea how to calculate the average TRB buffer length for bulk
742 * endpoints, as the driver gives us no clue how big each scatter gather
743 * list entry (or buffer) is going to be.
744 *
745 * For isochronous and interrupt endpoints, we set it to the max
746 * available, until we have new API in the USB core to allow drivers to
747 * declare how much bandwidth they actually need.
748 *
749 * Normally, it would be calculated by taking the total of the buffer
750 * lengths in the TD and then dividing by the number of TRBs in a TD,
751 * including link TRBs, No-op TRBs, and Event data TRBs. Since we don't
752 * use Event Data TRBs, and we don't chain in a link TRB on short
753 * transfers, we're basically dividing by 1.
754 */
755 ep_ctx->tx_info |= AVG_TRB_LENGTH_FOR_EP(max_esit_payload);
756
706 /* FIXME Debug endpoint context */ 757 /* FIXME Debug endpoint context */
707 return 0; 758 return 0;
708} 759}
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index e5eb09b2f38e..ea389e9a4931 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -609,6 +609,10 @@ struct xhci_ep_ctx {
609#define MAX_PACKET_MASK (0xffff << 16) 609#define MAX_PACKET_MASK (0xffff << 16)
610#define MAX_PACKET_DECODED(p) (((p) >> 16) & 0xffff) 610#define MAX_PACKET_DECODED(p) (((p) >> 16) & 0xffff)
611 611
612/* tx_info bitmasks */
613#define AVG_TRB_LENGTH_FOR_EP(p) ((p) & 0xffff)
614#define MAX_ESIT_PAYLOAD_FOR_EP(p) (((p) & 0xffff) << 16)
615
612 616
613/** 617/**
614 * struct xhci_input_control_context 618 * struct xhci_input_control_context