usb: xhci: Enable the TRB overfetch quirk on VIA VL805

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>
Link: https://lore.kernel.org/r/20250225095927.2512358-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 92703efda1f7b318f2f0c86d6427084fa8cab424..fdf0c1008225a2d540807b4727f840da71576b6a 100644 (file)
--- 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 ad0ff356f6fa0f3c2cb62e614b5e4f44486a577f..54460d11f7ee8120c03a9ab5603aab16c96a5073 100644 (file)
--- 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 8c164340a2c35099cedd081558236df3b1b5d14c..779b01dee068f5cae88ba28a4d17ff976f4dce97 100644 (file)
--- 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)