82 lines
2.7 KiB
Rust
82 lines
2.7 KiB
Rust
|
//! Boot Select button
|
||
|
|
//!
|
||
|
|
//! The RP2040 rom supports a BOOTSEL button that is used to enter the USB bootloader
|
||
|
|
//! if held during reset. To avoid wasting GPIO pins, the button is multiplexed onto
|
||
|
|
//! the CS pin of the QSPI flash, but that makes it somewhat expensive and complicated
|
||
|
|
//! to utilize outside of the rom's bootloader.
|
||
|
|
//!
|
||
|
|
//! This module provides functionality to poll BOOTSEL from an embassy application.
|
||
|
|
|
||
|
|
use crate::flash::in_ram;
|
||
|
|
|
||
|
|
/// Polls the BOOTSEL button. Returns true if the button is pressed.
|
||
|
|
///
|
||
|
|
/// Polling isn't cheap, as this function waits for core 1 to finish it's current
|
||
|
|
/// task and for any DMAs from flash to complete
|
||
|
|
pub fn poll_bootsel() -> bool {
|
||
|
|
let mut cs_status = Default::default();
|
||
|
|
|
||
|
|
unsafe { in_ram(|| cs_status = ram_helpers::read_cs_status()) }.expect("Must be called from Core 0");
|
||
|
|
|
||
|
|
// bootsel is active low, so invert
|
||
|
|
!cs_status.infrompad()
|
||
|
|
}
|
||
|
|
|
||
|
|
mod ram_helpers {
|
||
|
|
use rp_pac::io::regs::GpioStatus;
|
||
|
|
|
||
|
|
/// Temporally reconfigures the CS gpio and returns the GpioStatus.
|
||
|
|
|
||
|
|
/// This function runs from RAM so it can disable flash XIP.
|
||
|
|
///
|
||
|
|
/// # Safety
|
||
|
|
///
|
||
|
|
/// The caller must ensure flash is idle and will remain idle.
|
||
|
|
/// This function must live in ram. It uses inline asm to avoid any
|
||
|
|
/// potential calls to ABI functions that might be in flash.
|
||
|
|
#[inline(never)]
|
||
|
|
#[link_section = ".data.ram_func"]
|
||
|
|
#[cfg(target_arch = "arm")]
|
||
|
|
pub unsafe fn read_cs_status() -> GpioStatus {
|
||
|
|
let result: u32;
|
||
|
|
|
||
|
|
// Magic value, used as both OEOVER::DISABLE and delay loop counter
|
||
|
|
let magic = 0x2000;
|
||
|
|
|
||
|
|
core::arch::asm!(
|
||
|
|
".equiv GPIO_STATUS, 0x0",
|
||
|
|
".equiv GPIO_CTRL, 0x4",
|
||
|
|
|
||
|
|
"ldr {orig_ctrl}, [{cs_gpio}, $GPIO_CTRL]",
|
||
|
|
|
||
|
|
// The BOOTSEL pulls the flash's CS line low though a 1K resistor.
|
||
|
|
// this is weak enough to avoid disrupting normal operation.
|
||
|
|
// But, if we disable CS's output drive and allow it to float...
|
||
|
|
"str {val}, [{cs_gpio}, $GPIO_CTRL]",
|
||
|
|
|
||
|
|
// ...then wait for the state to settle...
|
||
|
|
"1:", // ~4000 cycle delay loop
|
||
|
|
"subs {val}, #8",
|
||
|
|
"bne 1b",
|
||
|
|
|
||
|
|
// ...we can read the current state of bootsel
|
||
|
|
"ldr {val}, [{cs_gpio}, $GPIO_STATUS]",
|
||
|
|
|
||
|
|
// Finally, restore CS to normal operation so XIP can continue
|
||
|
|
"str {orig_ctrl}, [{cs_gpio}, $GPIO_CTRL]",
|
||
|
|
|
||
|
|
cs_gpio = in(reg) rp_pac::IO_QSPI.gpio(1).as_ptr(),
|
||
|
|
orig_ctrl = out(reg) _,
|
||
|
|
val = inout(reg) magic => result,
|
||
|
|
options(nostack),
|
||
|
|
);
|
||
|
|
|
||
|
|
core::mem::transmute(result)
|
||
|
|
}
|
||
|
|
|
||
|
|
#[cfg(not(target_arch = "arm"))]
|
||
|
|
pub unsafe fn read_cs_status() -> GpioStatus {
|
||
|
|
unimplemented!()
|
||
|
|
}
|
||
|
|
}
|