2.6.31-stable review patch. If anyone has any objections, please let us know. ------------------ From: Sarah Sharp commit b0567b3f635db72c881a0d561cebb544ec085073 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-hcd.c | 12 ++++++++++++ drivers/usb/host/xhci-mem.c | 3 +++ drivers/usb/host/xhci-ring.c | 15 +++++++++++---- drivers/usb/host/xhci.h | 9 +++++++++ 4 files changed, 35 insertions(+), 4 deletions(-) --- 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 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); --- a/drivers/usb/host/xhci-hcd.c +++ b/drivers/usb/host/xhci-hcd.c @@ -22,12 +22,18 @@ #include #include +#include #include "xhci.h" #define DRIVER_AUTHOR "Sarah Sharp" #define DRIVER_DESC "'eXtensible' Host Controller (xHC) Driver" +/* Some 0.95 hardware can't handle the chain bit on a Link TRB being cleared */ +static int link_quirk; +module_param(link_quirk, int, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(link_quirk, "Don't clear the chain bit on a link TRB"); + /* TODO: copied from ehci-hcd.c - can this be refactored? */ /* * handshake - spin reading hc until handshake completes or fails @@ -214,6 +220,12 @@ int xhci_init(struct usb_hcd *hcd) xhci_dbg(xhci, "xhci_init\n"); spin_lock_init(&xhci->lock); + if (link_quirk) { + xhci_dbg(xhci, "QUIRK: Not clearing Link TRB chain bits.\n"); + xhci->quirks |= XHCI_LINK_TRB_QUIRK; + } else { + xhci_dbg(xhci, "xHCI has no QUIRKS\n"); + } retval = xhci_mem_init(xhci, GFP_KERNEL); xhci_dbg(xhci, "Finished xhci_init\n"); --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -94,6 +94,9 @@ static void xhci_link_segments(struct xh val = prev->trbs[TRBS_PER_SEGMENT-1].link.control; val &= ~TRB_TYPE_BITMASK; val |= TRB_TYPE(TRB_LINK); + /* Always set the chain bit with 0.95 hardware */ + if (xhci_link_trb_quirk(xhci)) + val |= TRB_CHAIN; prev->trbs[TRBS_PER_SEGMENT-1].link.control = val; } xhci_dbg(xhci, "Linking segment 0x%llx to segment 0x%llx (DMA)\n", --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -172,8 +172,9 @@ static void inc_deq(struct xhci_hcd *xhc * have their chain bit cleared (so that each Link TRB is a separate TD). * * Section 6.4.4.1 of the 0.95 spec says link TRBs cannot have the chain bit - * set, but other sections talk about dealing with the chain bit set. - * Assume section 6.4.4.1 is wrong, and the chain bit can be set in a Link TRB. + * set, but other sections talk about dealing with the chain bit set. This was + * fixed in the 0.96 specification errata, but we have to assume that all 0.95 + * xHCI hardware can't handle the chain bit being cleared on a link TRB. */ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer) { @@ -191,8 +192,14 @@ static void inc_enq(struct xhci_hcd *xhc while (last_trb(xhci, ring, ring->enq_seg, next)) { if (!consumer) { if (ring != xhci->event_ring) { - next->link.control &= ~TRB_CHAIN; - next->link.control |= chain; + /* If we're not dealing with 0.95 hardware, + * carry over the chain bit of the previous TRB + * (which may mean the chain bit is cleared). + */ + if (!xhci_link_trb_quirk(xhci)) { + next->link.control &= ~TRB_CHAIN; + next->link.control |= chain; + } /* Give this link TRB to the hardware */ wmb(); if (next->link.control & TRB_CYCLE) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/