Added anomaly workaround from the HAL to improve the UARTE

1 files changed, 56 insertions, 0 deletions

diff --git a/embassy-nrf/src/uarte.rs b/embassy-nrf/src/uarte.rs
index 320426060..15ebcdd57 100644
--- a/embassy-nrf/src/uarte.rs
+++ b/embassy-nrf/src/uarte.rs
@@ -114,6 +114,7 @@ impl<'d, T: Instance> Uarte<'d, T> {
         irq.enable();
 
         // Enable
+        Self::apply_workaround_for_enable_anomaly();
         r.enable.write(|w| w.enable().enabled());
 
         Self {
@@ -121,6 +122,61 @@ impl<'d, T: Instance> Uarte<'d, T> {
         }
     }
 
+    #[cfg(not(any(feature = "nrf9160", feature = "nrf5340")))]
+    fn apply_workaround_for_enable_anomaly() {
+        // Do nothing
+    }
+
+    #[cfg(any(feature = "nrf9160", feature = "nrf5340"))]
+    fn apply_workaround_for_enable_anomaly() {
+        use core::ops::Deref;
+
+        let r = T::regs();
+
+        // Apply workaround for anomalies:
+        // - nRF9160 - anomaly 23
+        // - nRF5340 - anomaly 44
+        let rxenable_reg: *const u32 = ((r.deref() as *const _ as usize) + 0x564) as *const u32;
+        let txenable_reg: *const u32 = ((r.deref() as *const _ as usize) + 0x568) as *const u32;
+
+        // NB Safety: This is taken from Nordic's driver -
+        // https://github.com/NordicSemiconductor/nrfx/blob/master/drivers/src/nrfx_uarte.c#L197
+        if unsafe { core::ptr::read_volatile(txenable_reg) } == 1 {
+            r.tasks_stoptx.write(|w| unsafe { w.bits(1) });
+        }
+
+        // NB Safety: This is taken from Nordic's driver -
+        // https://github.com/NordicSemiconductor/nrfx/blob/master/drivers/src/nrfx_uarte.c#L197
+        if unsafe { core::ptr::read_volatile(rxenable_reg) } == 1 {
+            r.enable.write(|w| w.enable().enabled());
+            r.tasks_stoprx.write(|w| unsafe { w.bits(1) });
+
+            let mut workaround_succeded = false;
+            // The UARTE is able to receive up to four bytes after the STOPRX task has been triggered.
+            // On lowest supported baud rate (1200 baud), with parity bit and two stop bits configured
+            // (resulting in 12 bits per data byte sent), this may take up to 40 ms.
+            for _ in 0..40000 {
+                // NB Safety: This is taken from Nordic's driver -
+                // https://github.com/NordicSemiconductor/nrfx/blob/master/drivers/src/nrfx_uarte.c#L197
+                if unsafe { core::ptr::read_volatile(rxenable_reg) } == 0 {
+                    workaround_succeded = true;
+                    break;
+                } else {
+                    // Need to sleep for 1us here
+                }
+            }
+
+            if !workaround_succeded {
+                panic!("Failed to apply workaround for UART");
+            }
+
+            let errors = r.errorsrc.read().bits();
+            // NB Safety: safe to write back the bits we just read to clear them
+            r.errorsrc.write(|w| unsafe { w.bits(errors) });
+            r.enable.write(|w| w.enable().disabled());
+        }
+    }
+
     fn on_interrupt(_: *mut ()) {
         let r = T::regs();
         let s = T::state();