| // SPDX-License-Identifier: Apache-2.0 OR MIT |
| |
| // Adapted from https://github.com/Rahix/avr-device. |
| // |
| // Refs: |
| // - AVR Instruction Set Manual https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf |
| |
| #[cfg(not(portable_atomic_no_asm))] |
| use core::arch::asm; |
| |
| pub(super) type State = u8; |
| |
| /// Disables interrupts and returns the previous interrupt state. |
| #[inline] |
| pub(super) fn disable() -> State { |
| let sreg: State; |
| // SAFETY: reading the status register (SREG) and disabling interrupts are safe. |
| // (see module-level comments of interrupt/mod.rs on the safety of using privileged instructions) |
| unsafe { |
| // Do not use `nomem` and `readonly` because prevent subsequent memory accesses from being reordered before interrupts are disabled. |
| // Do not use `preserves_flags` because CLI modifies the I bit of the status register (SREG). |
| // Refs: https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf#page=58 |
| #[cfg(not(portable_atomic_no_asm))] |
| asm!( |
| "in {0}, 0x3F", |
| "cli", |
| out(reg) sreg, |
| options(nostack), |
| ); |
| #[cfg(portable_atomic_no_asm)] |
| { |
| llvm_asm!("in $0, 0x3F" : "=r"(sreg) ::: "volatile"); |
| llvm_asm!("cli" ::: "memory" : "volatile"); |
| } |
| } |
| sreg |
| } |
| |
| /// Restores the previous interrupt state. |
| /// |
| /// # Safety |
| /// |
| /// The state must be the one retrieved by the previous `disable`. |
| #[inline] |
| pub(super) unsafe fn restore(sreg: State) { |
| // SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`, |
| unsafe { |
| // This clobbers the entire status register. See msp430.rs to safety on this. |
| // |
| // Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled. |
| // Do not use `preserves_flags` because OUT modifies the status register (SREG). |
| #[cfg(not(portable_atomic_no_asm))] |
| asm!("out 0x3F, {0}", in(reg) sreg, options(nostack)); |
| #[cfg(portable_atomic_no_asm)] |
| llvm_asm!("out 0x3F, $0" :: "r"(sreg) : "memory" : "volatile"); |
| } |
| } |