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machine/rp2040: always use the USB device enum fix #3905

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Sep 12, 2023
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machine/rp2040: always use the USB device enum fix #3905

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32 changes: 16 additions & 16 deletions src/machine/machine_rp2040_usb_fix_usb_device_enumeration.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,21 +8,21 @@ import (
)

// https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/pico_fix/rp2040_usb_device_enumeration/rp2040_usb_device_enumeration.c
// According to errata RP2040-E5:
// "It is safe (and inexpensive) to enable the software workaround even when using versions of RP2040
// which include the fix in hardware."
// So let us always use the software fix.
func fixRP2040UsbDeviceEnumeration() {

// Actually check for B0/B1 h/w
if ChipVersion() == 1 {
// After coming out of reset, the hardware expects 800us of LS_J (linestate J) time
// before it will move to the connected state. However on a hub that broadcasts packets
// for other devices this isn't the case. The plan here is to wait for the end of the bus
// reset, force an LS_J for 1ms and then switch control back to the USB phy. Unfortunately
// this requires us to use GPIO15 as there is no other way to force the input path.
// We only need to force DP as DM can be left at zero. It will be gated off by GPIO
// logic if it isn't func selected.

// Wait SE0 phase will call force ls_j phase which will call finish phase
hw_enumeration_fix_wait_se0()
}
// After coming out of reset, the hardware expects 800us of LS_J (linestate J) time
// before it will move to the connected state. However on a hub that broadcasts packets
// for other devices this isn't the case. The plan here is to wait for the end of the bus
// reset, force an LS_J for 1ms and then switch control back to the USB phy. Unfortunately
// this requires us to use GPIO15 as there is no other way to force the input path.
// We only need to force DP as DM can be left at zero. It will be gated off by GPIO
// logic if it isn't func selected.

// Wait SE0 phase will call force ls_j phase which will call finish phase
hw_enumeration_fix_wait_se0()
}

func hw_enumeration_fix_wait_se0() {
Expand Down Expand Up @@ -87,8 +87,8 @@ func hw_enumeration_fix_force_ls_j() {
// Switch to GPIO phy with LS_J forced
rp.USBCTRL_REGS.USB_MUXING.Set(rp.USBCTRL_REGS_USB_MUXING_TO_DIGITAL_PAD | rp.USBCTRL_REGS_USB_MUXING_SOFTCON)

// LS_J is now forced but while loop here just to check
waitCycles(125000)
// LS_J is now forced but while loop to wait ~800us here just to check
waitCycles(25000)

// if timer pool disabled, or no timer available, have to busy wait.
hw_enumeration_fix_finish()
Expand Down
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