From: Michal Pecio michal.pecio@gmail.com
Raspberry Pi is a major user of those chips and they discovered a bug - when the end of a transfer ring segment is reached, up to four TRBs can be prefetched from the next page even if the segment ends with link TRB and on page boundary (the chip claims to support standard 4KB pages).
It also appears that if the prefetched TRBs belong to a different ring whose doorbell is later rung, they may be used without refreshing from system RAM and the endpoint will stay idle if their cycle bit is stale.
Other users complain about IOMMU faults on x86 systems, unsurprisingly.
Deal with it by using existing quirk which allocates a dummy page after each transfer ring segment. This was seen to resolve both problems. RPi came up with a more efficient solution, shortening each segment by four TRBs, but it complicated the driver and they ditched it for this quirk.
Also rename the quirk and add VL805 device ID macro.
Signed-off-by: Michal Pecio michal.pecio@gmail.com Link: https://github.com/raspberrypi/linux/issues/4685 Closes: https://bugzilla.kernel.org/show_bug.cgi?id=215906 CC: stable@vger.kernel.org Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com --- drivers/usb/host/xhci-mem.c | 3 ++- drivers/usb/host/xhci-pci.c | 10 +++++++--- drivers/usb/host/xhci.h | 2 +- 3 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c index 92703efda1f7..fdf0c1008225 100644 --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -2437,7 +2437,8 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags) * and our use of dma addresses in the trb_address_map radix tree needs * TRB_SEGMENT_SIZE alignment, so we pick the greater alignment need. */ - if (xhci->quirks & XHCI_ZHAOXIN_TRB_FETCH) + if (xhci->quirks & XHCI_TRB_OVERFETCH) + /* Buggy HC prefetches beyond segment bounds - allocate dummy space at the end */ xhci->segment_pool = dma_pool_create("xHCI ring segments", dev, TRB_SEGMENT_SIZE * 2, TRB_SEGMENT_SIZE * 2, xhci->page_size * 2); else diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c index ad0ff356f6fa..54460d11f7ee 100644 --- a/drivers/usb/host/xhci-pci.c +++ b/drivers/usb/host/xhci-pci.c @@ -38,6 +38,8 @@ #define PCI_DEVICE_ID_ETRON_EJ168 0x7023 #define PCI_DEVICE_ID_ETRON_EJ188 0x7052
+#define PCI_DEVICE_ID_VIA_VL805 0x3483 + #define PCI_DEVICE_ID_INTEL_LYNXPOINT_XHCI 0x8c31 #define PCI_DEVICE_ID_INTEL_LYNXPOINT_LP_XHCI 0x9c31 #define PCI_DEVICE_ID_INTEL_WILDCATPOINT_LP_XHCI 0x9cb1 @@ -418,8 +420,10 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci) pdev->device == 0x3432) xhci->quirks |= XHCI_BROKEN_STREAMS;
- if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == 0x3483) + if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == PCI_DEVICE_ID_VIA_VL805) { xhci->quirks |= XHCI_LPM_SUPPORT; + xhci->quirks |= XHCI_TRB_OVERFETCH; + }
if (pdev->vendor == PCI_VENDOR_ID_ASMEDIA && pdev->device == PCI_DEVICE_ID_ASMEDIA_1042_XHCI) { @@ -467,11 +471,11 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci)
if (pdev->device == 0x9202) { xhci->quirks |= XHCI_RESET_ON_RESUME; - xhci->quirks |= XHCI_ZHAOXIN_TRB_FETCH; + xhci->quirks |= XHCI_TRB_OVERFETCH; }
if (pdev->device == 0x9203) - xhci->quirks |= XHCI_ZHAOXIN_TRB_FETCH; + xhci->quirks |= XHCI_TRB_OVERFETCH; }
if (pdev->vendor == PCI_VENDOR_ID_CDNS && diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h index 8c164340a2c3..779b01dee068 100644 --- a/drivers/usb/host/xhci.h +++ b/drivers/usb/host/xhci.h @@ -1632,7 +1632,7 @@ struct xhci_hcd { #define XHCI_EP_CTX_BROKEN_DCS BIT_ULL(42) #define XHCI_SUSPEND_RESUME_CLKS BIT_ULL(43) #define XHCI_RESET_TO_DEFAULT BIT_ULL(44) -#define XHCI_ZHAOXIN_TRB_FETCH BIT_ULL(45) +#define XHCI_TRB_OVERFETCH BIT_ULL(45) #define XHCI_ZHAOXIN_HOST BIT_ULL(46) #define XHCI_WRITE_64_HI_LO BIT_ULL(47) #define XHCI_CDNS_SCTX_QUIRK BIT_ULL(48)