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hal: Fix USB DWC HAL host channel halt race condition

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This commit fixes a race condtion bug with usb_dwc_hal_chan_request_halt()
where a channel the channel is halted if it has just completed a transfer
(i.e., finished processing a QTD with the "HOC" flag set) but the channel is
still pending interrupt handling. In this case...

- usb_dwc_hal_chan_request_halt() would simply read the channel's underlying
register, determine it is not active, not set the "halt_requested" flag, and
simply return true.
- The caller assumes of usb_dwc_hal_chan_request_halt() will assume that the
channel has halted, and may proceed to reconfigure the pipe/port
- When usb_dwc_hal_chan_decode_intr() comes to process the pending interrupt
it will simply return USB_DWC_HAL_CHAN_EVENT_CPLT not knowing a halt has been
requested.

This commit updates the implementation of usb_dwc_hal_chan_request_halt() so
that a halt is properly requested even if the underlying channel has already
physically halted.
This commit is contained in:
Darian Leung 2022-12-05 23:22:25 +08:00
parent 67507baf37
commit d69d1aafaf
1 changed files with 15 additions and 6 deletions
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21
components/hal/usb_dwc_hal.c
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@ -279,16 +279,21 @@ void usb_dwc_hal_chan_activate(usb_dwc_hal_chan_t *chan_obj, void *xfer_desc_lis
bool usb_dwc_hal_chan_request_halt(usb_dwc_hal_chan_t *chan_obj)
{
//Cannot request halt on a channel that is pending error handling
if (usb_dwc_ll_hcchar_chan_is_enabled(chan_obj->regs)) {
//If the register indicates that the channel is still active, the active flag must have been previously set
HAL_ASSERT(chan_obj->flags.active);
if (chan_obj->flags.active) {
/*
Request a halt so long as the channel's active flag is set.
- If the underlying hardware channel is already halted but the channel is pending interrupt handling,
disabling the channel will have no effect (i.e., no channel interrupt is generated).
- If the underlying channel is currently active, disabling the channel will trigger a channel interrupt.
Regardless, setting the "halt_requested" should cause "usb_dwc_hal_chan_decode_intr()" to report the
USB_DWC_HAL_CHAN_EVENT_HALT_REQ event when channel interrupt is handled (pending or triggered).
*/
usb_dwc_ll_hcchar_disable_chan(chan_obj->regs);
chan_obj->flags.halt_requested = 1;
return false;
} else {
//We just clear the active flag here as it could still be set (if we have a pending channel interrupt)
chan_obj->flags.active = 0;
//Channel was never active to begin with, simply return true
return true;
}
}
@ -359,6 +364,10 @@ usb_dwc_hal_chan_event_t usb_dwc_hal_chan_decode_intr(usb_dwc_hal_chan_t *chan_o
usb_dwc_hal_chan_event_t chan_event;
//Note: We don't assert on (chan_obj->flags.active) here as it could have been already cleared by usb_dwc_hal_chan_request_halt()
/*
Note: Do not change order of checks as some events take precedence over others.
Errors > Channel Halt Request > Transfer completed
*/
if (chan_intrs & CHAN_INTRS_ERROR_MSK) { //Note: Errors are uncommon, so we check against the entire interrupt mask to reduce frequency of entering this call path
HAL_ASSERT(chan_intrs & USB_DWC_LL_INTR_CHAN_CHHLTD); //An error should have halted the channel
//Store the error in hal context