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usb: dwc2: masquerade split-interrupt transfers #6936

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usb: dwc2: masquerade split-interrupt transfers #6936

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6727dfe
usb: dwc2: masquerade split-interrupt transfers
P33M Jun 24, 2025
9d4c59b
Fixup! usb: dwc2: limit "maximum packet size" for split-IN transfers
P33M Jul 4, 2025
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13 changes: 13 additions & 0 deletions drivers/usb/dwc2/hcd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -676,6 +676,18 @@ static void dwc2_hc_init(struct dwc2_hsotg *hsotg, struct dwc2_host_chan *chan)
hcchar |= HCCHAR_EPDIR;
if (chan->speed == USB_SPEED_LOW)
hcchar |= HCCHAR_LSPDDEV;

/*
* Masquerading Interrupt split transfers as Control puts the transfer
* into the non-periodic handler in the hub. This stops the hub
* dropping complete-split data in the microframe after a CSPLIT
* should have arrived, improving resilience to host IRQ latency.
* Devices are none the wiser - the handshake tokens are the same.
* The fakery is undone in dwc2_hc_n_intr().
*/
if (chan->do_split && chan->ep_type == USB_ENDPOINT_XFER_INT)
chan->ep_type = USB_ENDPOINT_XFER_CONTROL;

hcchar |= chan->ep_type << HCCHAR_EPTYPE_SHIFT & HCCHAR_EPTYPE_MASK;
hcchar |= chan->max_packet << HCCHAR_MPS_SHIFT & HCCHAR_MPS_MASK;
dwc2_writel(hsotg, hcchar, HCCHAR(hc_num));
Expand Down Expand Up @@ -2338,6 +2350,7 @@ static void dwc2_hc_init_xfer(struct dwc2_hsotg *hsotg,
else
chan->xfer_buf = urb->setup_packet;
chan->xfer_len = 8;
chan->max_packet = 8;
break;

case DWC2_CONTROL_DATA:
Expand Down
3 changes: 3 additions & 0 deletions drivers/usb/dwc2/hcd_intr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2048,6 +2048,9 @@ static void dwc2_hc_n_intr(struct dwc2_hsotg *hsotg, int chnum)

chan->hcint = hcintraw;

/* Un-masquerade the transfer type */
if (chan->do_split)
chan->ep_type = chan->qh->ep_type;
/*
* If the channel was halted due to a dequeue, the qtd list might
* be empty or at least the first entry will not be the active qtd.
Expand Down