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usb: dwc2: masquerade split-interrupt transfers

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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.

Originally devised by Hans Petter Selasky @ FreeBSD.

(v2: dwc2 needs an un-masquerade prior to channel interrupt handling)

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
This commit is contained in:
Jonathan Bell
2025-06-24 13:41:32 +01:00
committed by Dom Cobley
parent c39ae1cb2d
commit db7355a299
2 changed files with 15 additions and 0 deletions
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12
drivers/usb/dwc2/hcd.c
View File

@@ -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));

3
drivers/usb/dwc2/hcd_intr.c
View File

@@ -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.