[PATCH v2 1/3] usb: xhci: Add support for eUSB2v2 1024-byte bulk packet size
From: Pawel Laszczak via B4 Relay
Date: Wed Aug 26 2026 - 07:07:05 EST
From: Pawel Laszczak <pawell@xxxxxxxxxxx>
The eUSB2 v2 specification (bcdUSB 0x0230) introduces support for
1024-byte maximum packet sizes for Bulk endpoints in High-Speed mode.
However, an eUSB2v2 peripheral will revert its internal maximum packet
size back to 512 bytes after events like a bus reset, disconnect, or
deconfiguration.
To support 1024-byte bulk transfers on capable hosts, add a new
is_eusb2v2 flag to the usb_bus structure, populated via the HCCPARAMS2
E2V2C capability bit in the xHCI driver.
When an eUSB2v2 host configures an eUSB2v2 device, issue a specific
SET_FEATURE (USB_DEVICE_BULK_MAX_PACKET_UPDATE) request during device
configuration to switch the peripheral to 1024-byte packet mode, and
allow the xHCI endpoint initialization to accept up to 1024 bytes for
HS bulk endpoints.
Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
---
Changes in v2:
- Removed change in config.c: per eUSB2v2 spec section 5.2, conformant
devices always report wMaxPacketSize=512 in their descriptor regardless
of operating mode, so the warning suppression was unnecessary.
- xhci-mem.c: simplified HS bulk clamp
- xhci.c: moved is_eusb2v2 assignment into xhci_hcd_init_usb2_data()
- eusb_update_max_packet(): changed from void to int; returns error on
SET_FEATURE failure.
- Added eusb2v2_mps_active flag to struct usb_device to track whether
SET_FEATURE(BULK_MAX_PACKET_UPDATE) succeeded.
- Added hub.c: usb_reset_and_verify_device() now re-issues SET_FEATURE
after bus reset to restore 1KB mode. Failure triggers re-enumeration
to prevent a driver from operating with inconsistent MPS state.
---
drivers/usb/core/hub.c | 16 ++++++++++
drivers/usb/core/message.c | 74 ++++++++++++++++++++++++++++++++++++++++++++-
drivers/usb/core/usb.h | 2 ++
drivers/usb/host/xhci-mem.c | 18 +++++++++--
drivers/usb/host/xhci.c | 4 +++
include/linux/usb.h | 7 +++++
6 files changed, 117 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 24960ba9caa9..34cfc44c5df8 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -6252,6 +6252,22 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
mutex_unlock(hcd->bandwidth_mutex);
goto re_enumerate;
}
+
+ /*
+ * Restore eUSB2v2 1KB bulk mode after reset (device reverts to 512
+ * after any bus reset per eUSB2v2 spec section 5.2).
+ * Only retry if the initial SET_FEATURE had succeeded.
+ */
+ if (udev->eusb2v2_mps_active) {
+ ret = eusb_update_max_packet(udev, udev->actconfig);
+ if (ret < 0) {
+ dev_err(&udev->dev,
+ "eUSB2v2: failed to restore 1KB mode after reset (%d)\n", ret);
+ mutex_unlock(hcd->bandwidth_mutex);
+ goto re_enumerate;
+ }
+ }
+
ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
USB_REQ_SET_CONFIGURATION, 0,
udev->actconfig->desc.bConfigurationValue, 0,
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 75e2bfd744a9..18bedc7f91a3 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -2007,6 +2007,67 @@ int usb_set_wireless_status(struct usb_interface *iface,
}
EXPORT_SYMBOL_GPL(usb_set_wireless_status);
+/*
+ * eusb_update_max_packet - set or restore max packet size
+ * @udev: target device
+ * @cp: if NULL restore MPS to 512 else set 1024
+ *
+ * This request is specific to eUSB2v2.
+ * An eUSB2v2 peripheral will revert the maximum packet size to 512
+ * for bulk endpoints after bus reset, disconnect and deconfiguration.
+ * This function allows updating the max packet size for BULK endpoints
+ * to 1024 after above events.
+ */
+int eusb_update_max_packet(struct usb_device *udev, struct usb_host_config *cp)
+{
+ struct usb_host_config *config = cp ? cp : udev->actconfig;
+ struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+ struct usb_interface_cache *intfc;
+ struct usb_host_interface *alt;
+ struct usb_host_endpoint *ep;
+ u16 mps = 512;
+ int i, j, a;
+ int ret;
+
+ if (le16_to_cpu(udev->descriptor.bcdUSB) != 0x0230 ||
+ !hcd->self.is_eusb2v2)
+ return 0;
+
+ if (cp) {
+ ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+ USB_REQ_SET_FEATURE, USB_RECIP_DEVICE,
+ USB_DEVICE_BULK_MAX_PACKET_UPDATE, 0, NULL, 0,
+ USB_CTRL_SET_TIMEOUT);
+ if (ret < 0) {
+ dev_warn(&udev->dev, "eUSB2v2 1KB update failed: %d\n", ret);
+ return ret;
+ }
+
+ mps = 1024;
+ } else if (!udev->actconfig)
+ return 0;
+
+ for (i = 0; i < config->desc.bNumInterfaces; i++) {
+ intfc = config->intf_cache[i];
+
+ if (!intfc)
+ continue;
+
+ for (a = 0; a < intfc->num_altsetting; a++) {
+ alt = &intfc->altsetting[a];
+
+ for (j = 0; j < alt->desc.bNumEndpoints; j++) {
+ ep = &alt->endpoint[j];
+
+ if (usb_endpoint_xfer_bulk(&ep->desc))
+ ep->desc.wMaxPacketSize = cpu_to_le16(mps);
+ }
+ }
+ }
+
+ return 0;
+}
+
/*
* usb_set_configuration - Makes a particular device setting be current
* @dev: the device whose configuration is being updated
@@ -2120,8 +2181,19 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
/* if it's already configured, clear out old state first.
* getting rid of old interfaces means unbinding their drivers.
*/
- if (dev->state != USB_STATE_ADDRESS)
+ if (dev->state != USB_STATE_ADDRESS) {
+ eusb_update_max_packet(dev, NULL);
usb_disable_device(dev, 1); /* Skip ep0 */
+ }
+
+ ret = eusb_update_max_packet(dev, cp);
+ if (ret < 0)
+ dev->eusb2v2_mps_active = 0;
+ else if (le16_to_cpu(dev->descriptor.bcdUSB) == 0x0230 &&
+ hcd->self.is_eusb2v2)
+ dev->eusb2v2_mps_active = 1;
+ else
+ dev->eusb2v2_mps_active = 0;
/* Get rid of pending async Set-Config requests for this device */
cancel_async_set_config(dev);
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index a9b37aeb515b..c36fe2a2acea 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -89,6 +89,8 @@ extern int usb_major_init(void);
extern void usb_major_cleanup(void);
extern int usb_device_supports_lpm(struct usb_device *udev);
extern int usb_port_disable(struct usb_device *udev);
+extern int eusb_update_max_packet(struct usb_device *udev,
+ struct usb_host_config *cp);
#ifdef CONFIG_PM
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 997fe90f54e5..8ccbfaf57612 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1479,10 +1479,22 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
/* Allow 3 retries for everything but isoc, set CErr = 3 */
if (!usb_endpoint_xfer_isoc(&ep->desc))
err_count = 3;
- /* HS bulk max packet should be 512, FS bulk supports 8, 16, 32 or 64 */
+
+ /*
+ * HS bulk max packet should be 512 (or 1024 for eUSB2v2),
+ * FS bulk supports 8, 16, 32 or 64.
+ */
if (usb_endpoint_xfer_bulk(&ep->desc)) {
- if (udev->speed == USB_SPEED_HIGH)
- max_packet = 512;
+ if (udev->speed == USB_SPEED_HIGH) {
+ if (le16_to_cpu(udev->descriptor.bcdUSB) == 0x0230 &&
+ xhci->hcc_params2 & HCC2_E2V2C) {
+ if (max_packet != 1024)
+ max_packet = 512;
+ } else {
+ max_packet = 512;
+ }
+ }
+
if (udev->speed == USB_SPEED_FULL) {
max_packet = rounddown_pow_of_two(max_packet);
max_packet = clamp_val(max_packet, 8, 64);
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index a54f5b57f205..ba3cdc5c732d 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -5371,6 +5371,10 @@ static void xhci_hcd_init_usb2_data(struct xhci_hcd *xhci, struct usb_hcd *hcd)
xhci->usb2_rhub.hcd = hcd;
hcd->speed = HCD_USB2;
hcd->self.root_hub->speed = USB_SPEED_HIGH;
+
+ if (xhci->hcc_params2 & HCC2_E2V2C)
+ hcd->self.is_eusb2v2 = 1;
+
/*
* USB 2.0 roothub under xHCI has an integrated TT,
* (rate matching hub) as opposed to having an OHCI/UHCI
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 25a203ac7a7e..57fb4c552740 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -464,6 +464,10 @@ struct usb_bus {
* the ep queue on a short transfer
* with the URB_SHORT_NOT_OK flag set.
*/
+ unsigned is_eusb2v2:1; /*
+ * true when HC controller supports
+ * eusb2v2
+ */
unsigned no_sg_constraint:1; /* no sg constraint */
unsigned sg_tablesize; /* 0 or largest number of sg list entries */
@@ -625,6 +629,8 @@ struct usb3_lpm_parameters {
* @usb2_hw_lpm_allowed: Userspace allows USB 2.0 LPM to be enabled
* @usb3_lpm_u1_enabled: USB3 hardware U1 LPM enabled
* @usb3_lpm_u2_enabled: USB3 hardware U2 LPM enabled
+ * @eusb2v2_mps_active: 1024-byte bulk mode is active and must be restored
+ * after bus reset.
* @string_langid: language ID for strings
* @product: iProduct string, if present (static)
* @manufacturer: iManufacturer string, if present (static)
@@ -708,6 +714,7 @@ struct usb_device {
unsigned usb2_hw_lpm_allowed:1;
unsigned usb3_lpm_u1_enabled:1;
unsigned usb3_lpm_u2_enabled:1;
+ unsigned eusb2v2_mps_active:1;
int string_langid;
/* static strings from the device */
--
2.43.0