riscv: add mcounteren in-memory update functions

Adds functions for updating the in-memory `Mcounteren` structure without
touching the CSR.

Allows manipulating all bitfields in-memory, and writing the entire
value back to the CSR at once.

riscv/CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   the CSR
 - Export `riscv::register::macros` module macros for external use
 - Add `riscv::register::mcountinhibit` module for `mcountinhibit` CSR
+- Add `Mcounteren` in-memory update functions 
 
 ### Fixed
 

riscv/src/register/mcounteren.rs

@@ -1,6 +1,6 @@
 //! mcounteren register
 
-use crate::bits::bf_extract;
+use crate::bits::{bf_extract, bf_insert};
 
 /// mcounteren register
 #[derive(Clone, Copy, Debug)]
@@ -15,28 +15,61 @@ impl Mcounteren {
         bf_extract(self.bits, 0, 1) != 0
     }
 
+    /// Sets whether to enable the "cycle\[h\]" counter.
+    ///
+    /// Only updates the in-memory value, does not modify the `mcounteren` register.
+    #[inline]
+    pub fn set_cy(&mut self, cy: bool) {
+        self.bits = bf_insert(self.bits, 0, 1, cy as usize);
+    }
+
     /// Supervisor "time\[h\]" Enable
     #[inline]
     pub fn tm(&self) -> bool {
         bf_extract(self.bits, 1, 1) != 0
     }
 
+    /// Sets whether to enable "time\[h\]".
+    ///
+    /// Only updates the in-memory value, does not modify the `mcounteren` register.
+    #[inline]
+    pub fn set_tm(&mut self, tm: bool) {
+        self.bits = bf_insert(self.bits, 1, 1, tm as usize);
+    }
+
     /// Supervisor "instret\[h\]" Enable
     #[inline]
     pub fn ir(&self) -> bool {
         bf_extract(self.bits, 2, 1) != 0
     }
 
+    /// Sets whether to enable the "instret\[h\]" counter.
+    ///
+    /// Only updates the in-memory value, does not modify the `mcounteren` register.
+    #[inline]
+    pub fn set_ir(&mut self, ir: bool) {
+        self.bits = bf_insert(self.bits, 2, 1, ir as usize);
+    }
+
     /// Supervisor "hpm\[x\]" Enable (bits 3-31)
     #[inline]
     pub fn hpm(&self, index: usize) -> bool {
         assert!((3..32).contains(&index));
         bf_extract(self.bits, index, 1) != 0
     }
+
+    /// Sets whether to enable the "hpm\[X\]" counter.
+    ///
+    /// Only updates the in-memory value, does not modify the `mcounteren` register.
+    #[inline]
+    pub fn set_hpm(&mut self, index: usize, hpm: bool) {
+        assert!((3..32).contains(&index));
+        self.bits = bf_insert(self.bits, index, 1, hpm as usize);
+    }
 }
 
 read_csr_as!(Mcounteren, 0x306);
-write_csr!(0x306);
+write_csr_as!(Mcounteren, 0x306);
 set!(0x306);
 clear!(0x306);
 
@@ -63,3 +96,47 @@ pub unsafe fn clear_hpm(index: usize) {
     assert!((3..32).contains(&index));
     _clear(1 << index);
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mcounteren() {
+        let mut m = Mcounteren { bits: 0 };
+
+        assert!(!m.cy());
+
+        m.set_cy(true);
+        assert!(m.cy());
+
+        m.set_cy(false);
+        assert!(!m.cy());
+
+        assert!(!m.tm());
+
+        m.set_tm(true);
+        assert!(m.tm());
+
+        m.set_tm(false);
+        assert!(!m.tm());
+
+        assert!(!m.ir());
+
+        m.set_ir(true);
+        assert!(m.ir());
+
+        m.set_ir(false);
+        assert!(!m.ir());
+
+        (3..32).for_each(|i| {
+            assert!(!m.hpm(i));
+
+            m.set_hpm(i, true);
+            assert!(m.hpm(i));
+
+            m.set_hpm(i, false);
+            assert!(!m.hpm(i));
+        });
+    }
+}