Merge pull request #270 from hegza/pr/write-pcounters

riscv: make mcycle & minstret writable

riscv/CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- CSR helper macro `write_composite_csr` for writing 64-bit CSRs on 32-bit targets.
+- Write utilities for `mcycle`, `minstret`
+
 ## [v0.13.0] - 2025-02-18
 
 ### Added

riscv/src/register/macros.rs

@@ -449,6 +449,30 @@ macro_rules! read_composite_csr {
     };
 }
 
+/// Convenience macro to write a composite value to a CSR register.
+///
+/// - `RV32`: writes 32-bits into `hi` and 32-bits into `lo` to create a 64-bit value
+/// - `RV64`: writes a 64-bit value into `lo`
+#[macro_export]
+macro_rules! write_composite_csr {
+    ($hi:expr, $lo:expr) => {
+        /// Writes the CSR as a 64-bit value
+        #[inline]
+        pub unsafe fn write64(bits: u64) {
+            match () {
+                #[cfg(target_arch = "riscv32")]
+                () => {
+                    $hi((bits >> 32) as usize);
+                    $lo(bits as usize);
+                }
+
+                #[cfg(not(target_arch = "riscv32"))]
+                () => $lo(bits as usize),
+            }
+        }
+    };
+}
+
 macro_rules! set_pmp {
     () => {
         /// Set the pmp configuration corresponding to the index.

riscv/src/register/mcycle.rs

@@ -1,4 +1,6 @@
 //! mcycle register
 
 read_csr_as_usize!(0xB00);
+write_csr_as_usize!(0xB00);
 read_composite_csr!(super::mcycleh::read(), read());
+write_composite_csr!(super::mcycleh::write, write);

riscv/src/register/mcycleh.rs

@@ -1,3 +1,4 @@
 //! mcycleh register
 
 read_csr_as_usize_rv32!(0xB80);
+write_csr_as_usize_rv32!(0xB80);

riscv/src/register/minstret.rs

@@ -1,4 +1,6 @@
 //! minstret register
 
 read_csr_as_usize!(0xB02);
+write_csr_as_usize!(0xB02);
 read_composite_csr!(super::minstreth::read(), read());
+write_composite_csr!(super::minstreth::write, write);

riscv/src/register/minstreth.rs

@@ -1,3 +1,4 @@
 //! minstreth register
 
 read_csr_as_usize_rv32!(0xB82);
+write_csr_as_usize_rv32!(0xB82);