From b0567b3f635db72c881a0d561cebb544ec085073 Mon Sep 17 00:00:00 2001 From: Sarah Sharp Date: Fri, 7 Aug 2009 14:04:36 -0700 Subject: USB: xhci: Work around for chain bit in link TRBs. Different sections of the xHCI 0.95 specification had opposing requirements for the chain bit in a link transaction request buffer (TRB). The chain bit is used to designate that adjacent TRBs are all part of the same scatter gather list that should be sent to the device. Link TRBs can be in the middle, or at the beginning or end of these chained TRBs. Sections 4.11.5.1 and 6.4.4.1 both stated the link TRB "shall have the chain bit set to 1", meaning it is always chained to the next TRB. However, section 4.6.9 on the stop endpoint command has specific cases for what the hardware must do for a link TRB with the chain bit set to 0. The 0.96 specification errata later cleared up this issue by fixing the 4.11.5.1 and 6.4.4.1 sections to state that a link TRB can have the chain bit set to 1 or 0. The problem is that the xHCI cancellation code depends on the chain bit of the link TRB being cleared when it's at the end of a TD, and some 0.95 xHCI hardware simply stops processing the ring when it encounters a link TRB with the chain bit cleared. Allow users who are testing 0.95 xHCI prototypes to set a module parameter (link_quirk) to turn on this link TRB work around. Cancellation may not work if the ring is stopped exactly on a link TRB with chain bit set, but cancellation should be a relatively uncommon case. Signed-off-by: Sarah Sharp Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/usb/host/xhci.h') diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h index ffe1625d4e1b..79ea627e8b8a 100644 --- a/drivers/usb/host/xhci.h +++ b/drivers/usb/host/xhci.h @@ -1058,6 +1058,8 @@ struct xhci_hcd { int noops_submitted; int noops_handled; int error_bitmask; + unsigned int quirks; +#define XHCI_LINK_TRB_QUIRK (1 << 0) }; /* For testing purposes */ @@ -1136,6 +1138,13 @@ static inline void xhci_write_64(struct xhci_hcd *xhci, writel(val_hi, ptr + 1); } +static inline int xhci_link_trb_quirk(struct xhci_hcd *xhci) +{ + u32 temp = xhci_readl(xhci, &xhci->cap_regs->hc_capbase); + return ((HC_VERSION(temp) == 0x95) && + (xhci->quirks & XHCI_LINK_TRB_QUIRK)); +} + /* xHCI debugging */ void xhci_print_ir_set(struct xhci_hcd *xhci, struct xhci_intr_reg *ir_set, int set_num); void xhci_print_registers(struct xhci_hcd *xhci); -- cgit v1.2.2