[PATCH] usb: core: Fix bandwidth for devices with invalid wBytesPerInterval

Tao Xue
2026-04-02T02:14:53Z

As specified in Section 4.14.2 of the xHCI Specification, the xHC
reserves bandwidth for periodic endpoints according to bInterval and
wBytesPerInterval (Max ESIT Payload).

Some peripherals report an invalid wBytesPerInterval in their device
descriptor, which is either 0 or smaller than the actual data length
transmitted. This issue is observed on ASIX AX88179 series USB 3.0
Ethernet adapters.

These errors may lead to unexpected behavior on certain USB host
controllers, causing USB peripherals to malfunction.

To address the issue, return max(wBytesPerInterval, max_payload) when
calculating bandwidth reservation.

Fixes: 9238f25d5d32 ("USB: xhci: properly set endpoint context fields for periodic eps.")
Cc: <stable@kernel.org>
Signed-off-by: Tao Xue <xuetao09@huawei.com>
---
drivers/usb/core/usb.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index e9a10a33534c..8f2e05a5a015 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -1125,6 +1125,8 @@ EXPORT_SYMBOL_GPL(usb_free_noncoherent);
u32 usb_endpoint_max_periodic_payload(struct usb_device *udev,
const struct usb_host_endpoint *ep)
{
+ u32 max_payload;
+
if (!usb_endpoint_xfer_isoc(&ep->desc) &&
!usb_endpoint_xfer_int(&ep->desc))
return 0;
@@ -1135,7 +1137,12 @@ u32 usb_endpoint_max_periodic_payload(struct usb_device *udev,
return le32_to_cpu(ep->ssp_isoc_ep_comp.dwBytesPerInterval);
fallthrough;
case USB_SPEED_SUPER:
- return le16_to_cpu(ep->ss_ep_comp.wBytesPerInterval);
+ max_payload = usb_endpoint_maxp(&ep->desc) * (ep->ss_ep_comp.bMaxBurst + 1);
+ if (usb_endpoint_xfer_isoc(&ep->desc))
+ return max_t(u32, max_payload * USB_SS_MULT(ep->ss_ep_comp.bmAttributes),
+ ep->ss_ep_comp.wBytesPerInterval);
+ else
+ return max_t(u32, max_payload, ep->ss_ep_comp.wBytesPerInterval);
default:
if (usb_endpoint_is_hs_isoc_double(udev, ep))
return le32_to_cpu(ep->eusb2_isoc_ep_comp.dwBytesPerInterval);
--
2.17.1