Make EthernetDMA actually drop safe

Author: datdenkikniet

src/dma/mod.rs

@@ -281,6 +281,15 @@ impl<'rx, 'tx> EthernetDMA<'rx, 'tx> {
     }
 }
 
+impl Drop for EthernetDMA<'_, '_> {
+    // On drop, stop all DMA actions.
+    fn drop(&mut self) {
+        self.tx_ring.stop(&self.eth_dma);
+
+        self.rx_ring.stop(&self.eth_dma);
+    }
+}
+
 #[cfg(feature = "ptp")]
 impl EthernetDMA<'_, '_> {
     /// Try to get the timestamp for the given packet ID.

src/dma/rx/mod.rs

@@ -81,6 +81,16 @@ impl<'a> RxRing<'a> {
         self.demand_poll();
     }
 
+    /// Stop the RX DMA
+    pub(crate) fn stop(&self, eth_dma: &ETHERNET_DMA) {
+        eth_dma.dmaomr.modify(|_, w| w.sr().clear_bit());
+
+        // DMA accesses do not stop before the running state
+        // of the DMA has changed to something other than
+        // running.
+        while self.running_state().is_running() {}
+    }
+
     /// Demand that the DMA engine polls the current `RxDescriptor`
     /// (when in [`RunningState::Stopped`].)
     fn demand_poll(&self) {

src/dma/tx/mod.rs

@@ -68,6 +68,16 @@ impl<'ring> TxRing<'ring> {
         eth_dma.dmaomr.modify(|_, w| w.st().set_bit());
     }
 
+    /// Stop the TX DMA
+    pub(crate) fn stop(&self, eth_dma: &ETHERNET_DMA) {
+        eth_dma.dmaomr.modify(|_, w| w.st().clear_bit());
+
+        // DMA accesses do not stop before the running state
+        // of the DMA has changed to something other than
+        // running.
+        while self.is_running() {}
+    }
+
     /// If this returns `true`, the next `send` will succeed.
     pub fn next_entry_available(&self) -> bool {
         !self.entries[self.next_entry].is_available()