| // SPDX-License-Identifier: Apache-2.0 OR MIT |
| |
| // Adapted from https://github.com/rust-embedded/msp430. |
| // |
| // See also src/imp/msp430.rs. |
| // |
| // Refs: https://www.ti.com/lit/ug/slau208q/slau208q.pdf |
| |
| #[cfg(not(portable_atomic_no_asm))] |
| use core::arch::asm; |
| |
| pub(super) use super::super::msp430 as atomic; |
| |
| pub(super) type State = u16; |
| |
| /// Disables interrupts and returns the previous interrupt state. |
| #[inline] |
| pub(super) fn disable() -> State { |
| let r: State; |
| // SAFETY: reading the status register 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 DINT modifies the GIE (global interrupt enable) bit of the status register. |
| #[cfg(not(portable_atomic_no_asm))] |
| asm!( |
| "mov R2, {0}", |
| "dint {{ nop", |
| out(reg) r, |
| options(nostack), |
| ); |
| #[cfg(portable_atomic_no_asm)] |
| { |
| llvm_asm!("mov R2, $0" : "=r"(r) ::: "volatile"); |
| llvm_asm!("dint { nop" ::: "memory" : "volatile"); |
| } |
| } |
| r |
| } |
| |
| /// Restores the previous interrupt state. |
| /// |
| /// # Safety |
| /// |
| /// The state must be the one retrieved by the previous `disable`. |
| #[inline] |
| pub(super) unsafe fn restore(r: State) { |
| // SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`, |
| unsafe { |
| // This clobbers the entire status register, but we never explicitly modify |
| // flags within a critical session, and the only flags that may be changed |
| // within a critical session are the arithmetic flags that are changed as |
| // a side effect of arithmetic operations, etc., which LLVM recognizes, |
| // so it is safe to clobber them here. |
| // See also the discussion at https://github.com/taiki-e/portable-atomic/pull/40. |
| // |
| // Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled. |
| // Do not use `preserves_flags` because MOV modifies the status register. |
| #[cfg(not(portable_atomic_no_asm))] |
| asm!("nop {{ mov {0}, R2 {{ nop", in(reg) r, options(nostack)); |
| #[cfg(portable_atomic_no_asm)] |
| llvm_asm!("nop { mov $0, R2 { nop" :: "r"(r) : "memory" : "volatile"); |
| } |
| } |