Implement flash configuration

Author: Disasm

assemble.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+# remove existing blobs because otherwise this will append object files to the old blobs
+rm -f bin/*.a
+
+riscv64-unknown-elf-gcc -ggdb3 -fdebug-prefix-map=$(pwd)=/hifive1 -c -mabi=ilp32 -march=rv32imac flash.S -o bin/flash.o
+riscv64-unknown-elf-ar crs bin/flash.a bin/flash.o
+
+rm bin/flash.o

bin/flash.a

@@ -42,4 +42,10 @@ fn main() {
     }
 
     fs::copy("hifive1-link.x", out_dir.join("hifive1-link.x")).unwrap();
+
+    // Copy library with flash setup code
+    let name = env::var("CARGO_PKG_NAME").unwrap();
+    fs::copy("bin/flash.a", out_dir.join(format!("lib{}.a", name))).unwrap();
+    println!("cargo:rustc-link-lib=static={}", name);
+    println!("cargo:rerun-if-changed=bin/flash.a");
 }

build.rs

@@ -0,0 +1,45 @@
+.cfi_sections .debug_frame
+
+.section .data._setup_is25lp
+.global _setup_is25lp
+.cfi_startproc
+_setup_is25lp:
+    li  a1, 0x10014000  // QSPI0 base address
+
+    // Disable mapped region
+    sw  zero,96(a1)  // fctrl.en = 0
+
+    // Construct ffmt value for 4 dummy cycles
+    li  a2, 0x00BB1447
+
+    beqz a0, 2f
+
+    // We need to set 8 dummy cycles instead of 4.
+    // Issue a "Set Read Parameters" command.
+
+    li  a0,2
+    sw  a0,24(a1)  // csmode = HOLD
+    li  a0,0xC0
+    sw  a0,72(a1)  // txdata = 0xC0
+    li  a0,0xF0
+    sw  a0,72(a1)  // txdata = 0xF0
+    sw  zero,24(a1)  // csmode = AUTO
+
+    // Discard two response bytes
+1:  lw  a0,76(a1)
+    bltz a0,1b
+1:  lw  a0,76(a1)
+    bltz a0,1b
+
+    addi a2,a2,0x40  // ffmt: 4 -> 8 dummy cycles
+2:
+    sw  a2,100(a1)  // Write ffmt
+
+    // Enable mapped region
+    li  a0, 1
+    sw	a0,96(a1)  // fctrl.en = 1
+    ret
+
+
+.cfi_endproc
+.size _setup_is25lp, . - _setup_is25lp

flash.S

@@ -0,0 +1,21 @@
+//! On-board SPI Flash
+
+use e310x_hal::e310x::QSPI0;
+use e310x_hal::clock::Clocks;
+
+/// Configure SPI Flash interface to maximum supported speed
+#[inline(always)]
+pub fn configure_spi_flash(qspi: &QSPI0, clocks: &Clocks) {
+    unsafe {
+        extern "C" {
+            fn _setup_is25lp(dummy8: bool);
+        }
+
+        if clocks.coreclk().0 <= 208_000_000 {
+            _setup_is25lp(false)
+        } else {
+            _setup_is25lp(true)
+        }
+    }
+    qspi.sckdiv.modify(|_, w| unsafe { w.div().bits(0) });
+}

src/flash.rs

@@ -8,6 +8,8 @@ pub use e310x_hal as hal;
 pub mod clock;
 pub use clock::configure as configure_clocks;
 
+pub mod flash;
+
 #[cfg(any(feature = "board-hifive1", feature = "board-hifive1-revb"))]
 pub mod led;
 #[cfg(any(feature = "board-hifive1", feature = "board-hifive1-revb"))]