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work around possible RP2040 erratum

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RP2040 device controller does not seem to clear pending transactions
configured in EP0 buffer controls when the host aborts a control
transfer. This causes assertion failures, including when a buffer
AVAILABLE flag set for a previous transfer causes an unexpected
transaction completion.
This commit is contained in:
Taylor Yu 2024-02-25 11:12:24 -06:00
parent f21b792712
commit 473d400cfd
1 changed files with 31 additions and 0 deletions
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31
src/portable/raspberrypi/rp2040/dcd_rp2040.c
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@ -217,6 +217,18 @@ static void __tusb_irq_path_func(hw_handle_buff_status)(void)
TU_ATTR_ALWAYS_INLINE static inline void reset_ep0_pid(void)
{
// Abort any transactions from a prior control transfer, because
// receiving SETUP doesn't reset buffer control state. This works around
// a possible USB hardware erratum.
// With this workaround a race window still exists, but smaller.
// ABORT flag is unusable prior to hardware B2 (RP2040-E2), so a larger
// race window exists for B1 and earlier.
if (rp2040_chip_version() >= 2) {
usb_hw_set->abort = 0x3;
while ((usb_hw->abort_done & 0x3) != 0x3)
;
}
// If we have finished this transfer on EP0 set pid back to 1 for next
// setup transfer. Also clear a stall in case
uint8_t addrs[] = {0x0, 0x80};
@ -224,6 +236,25 @@ TU_ATTR_ALWAYS_INLINE static inline void reset_ep0_pid(void)
{
struct hw_endpoint *ep = hw_endpoint_get_by_addr(addrs[i]);
ep->next_pid = 1u;
// Reset the buffer control now to minimize race conditions
_hw_endpoint_buffer_control_set_value32(ep, USB_BUF_CTRL_DATA1_PID | USB_BUF_CTRL_SEL);
// Explicit delay, because the one in
// _hw_endpoint_buffer_control_set_value32 is only to set AVAILABLE
__asm volatile (
"b 1f\n"
"1: b 1f\n"
"1: b 1f\n"
"1: b 1f\n"
"1: b 1f\n"
"1: b 1f\n"
"1:\n"
: : : "memory");
// Make sure local ep state matches peripheral
hw_endpoint_reset_transfer(ep);
}
if (rp2040_chip_version() >= 2) {
usb_hw_clear->abort = 0x3;
usb_hw_clear->abort_done = 0x3;
}
}