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Merge #186

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186: [backport] unlock the DWT, if locked, when using the timer queue r=korken89 a=japaric

**HEADS UP** this PR targets the branch v0.4.x

Co-authored-by: Jorge Aparicio <jorge@japaric.io>
Co-authored-by: Emil Fresk <emil.fresk@gmail.com>
This commit is contained in:
bors[bot] 2019-10-23 20:49:30 +00:00 committed by GitHub
commit 1fb1dd466b
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macros/src/codegen.rs
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@ -2023,6 +2023,16 @@ fn pre_init(ctxt: &Context, app: &App, analysis: &Analysis) -> proc_macro2::Toke
// Set the cycle count to 0 and disable it while `init` executes
if cfg!(feature = "timer-queue") {
exprs.push(quote!(
// unlock the DWT, if software locked
// See ARM CoreSight Architecture Specification v3.0, section B2.3.10
// 1 << 0 = Software lock mechanism is implemented.
// 1 << 1 = Writing to the other registers in the component is blocked
if p.DWT.lsr.read() & 0b11 == 0b11 {
p.DWT.lar.write(0xC5ACCE55);
}
));
// We need to explicitly enable the trace block to set CYCCNT.
exprs.push(quote!(p.DCB.enable_trace();));
exprs.push(quote!(p.DWT.ctrl.modify(|r| r & !1);));