Enable LPSPI watermark change while enabled

Unlike LPUART, there's no requirement to be disabled while changing
this. Keep the existing API, and point users towards the new method.

Co-authored-by: Ian McIntyre <[email protected]>

CHANGELOG.md

@@ -14,6 +14,8 @@ Introduce LPSPI improvements:
 - Add `soft_reset()` method.
 - Allow users to change the mode while enabled. Deprecate the corresponding
   method on the `Disabled` helper.
+- Allow users to change the watermark while enabled. Deprecate the corresponding
+  method on the `Disabled` helper.
 
 ## [0.5.4] 2023-11-26
 

examples/rtic_spi.rs

@@ -25,12 +25,10 @@ mod app {
     #[init]
     fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
         let (_, board::Specifics { mut spi, .. }) = board::new();
-        spi.disabled(|spi| {
-            // Trigger when the TX FIFO is empty.
-            spi.set_watermark(Direction::Tx, 0);
-            // Wait to receive at least 2 u32s.
-            spi.set_watermark(Direction::Rx, 1);
-        });
+        // Trigger when the TX FIFO is empty.
+        spi.set_watermark(Direction::Tx, 0);
+        // Wait to receive at least 2 u32s.
+        spi.set_watermark(Direction::Rx, 1);
         // Starts the I/O as soon as we're done initializing, since
         // the TX FIFO is empty.
         spi.set_interrupts(Interrupts::TRANSMIT_DATA);

src/common/lpspi.rs

@@ -898,6 +898,21 @@ impl<P, const N: u8> Lpspi<P, N> {
         // Restore enabled state
         self.set_enable(enabled);
     }
+
+    /// Set the watermark level for a given direction.
+    ///
+    /// Returns the watermark level committed to the hardware. This may be different
+    /// than the supplied `watermark`, since it's limited by the hardware.
+    ///
+    /// When `direction == Direction::Rx`, the receive data flag is set whenever the
+    /// number of words in the receive FIFO is greater than `watermark`.
+    ///
+    /// When `direction == Direction::Tx`, the transmit data flag is set whenever the
+    /// the number of words in the transmit FIFO is less than, or equal, to `watermark`.
+    #[inline]
+    pub fn set_watermark(&mut self, direction: Direction, watermark: u8) -> u8 {
+        set_watermark(&self.lpspi, direction, watermark)
+    }
 }
 
 bitflags::bitflags! {
@@ -1029,6 +1044,27 @@ bitflags::bitflags! {
     }
 }
 
+#[inline]
+fn set_watermark(lpspi: &ral::lpspi::RegisterBlock, direction: Direction, watermark: u8) -> u8 {
+    let max_watermark = match direction {
+        Direction::Rx => 1 << ral::read_reg!(ral::lpspi, lpspi, PARAM, RXFIFO),
+        Direction::Tx => 1 << ral::read_reg!(ral::lpspi, lpspi, PARAM, TXFIFO),
+    };
+
+    let watermark = watermark.min(max_watermark - 1);
+
+    match direction {
+        Direction::Rx => {
+            ral::modify_reg!(ral::lpspi, lpspi, FCR, RXWATER: watermark as u32)
+        }
+        Direction::Tx => {
+            ral::modify_reg!(ral::lpspi, lpspi, FCR, TXWATER: watermark as u32)
+        }
+    }
+
+    watermark
+}
+
 /// An LPSPI peripheral which is temporarily disabled.
 pub struct Disabled<'a, const N: u8> {
     lpspi: &'a ral::lpspi::Instance<N>,
@@ -1076,24 +1112,12 @@ impl<'a, const N: u8> Disabled<'a, N> {
     /// When `direction == Direction::Tx`, the transmit data flag is set whenever the
     /// the number of words in the transmit FIFO is less than, or equal, to `watermark`.
     #[inline]
+    #[deprecated(
+        since = "0.5.5",
+        note = "Use Lpspi::set_watermark to change watermark while enabled"
+    )]
     pub fn set_watermark(&mut self, direction: Direction, watermark: u8) -> u8 {
-        let max_watermark = match direction {
-            Direction::Rx => 1 << ral::read_reg!(ral::lpspi, self.lpspi, PARAM, RXFIFO),
-            Direction::Tx => 1 << ral::read_reg!(ral::lpspi, self.lpspi, PARAM, TXFIFO),
-        };
-
-        let watermark = watermark.min(max_watermark - 1);
-
-        match direction {
-            Direction::Rx => {
-                ral::modify_reg!(ral::lpspi, self.lpspi, FCR, RXWATER: watermark as u32)
-            }
-            Direction::Tx => {
-                ral::modify_reg!(ral::lpspi, self.lpspi, FCR, TXWATER: watermark as u32)
-            }
-        }
-
-        watermark
+        set_watermark(self.lpspi, direction, watermark)
     }
 
     /// Set the sampling point of the LPSPI peripheral.