From 2f48ad5f404c5deb129dfaca26856627f2515971 Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Date: Thu, 5 Sep 2024 16:59:06 +0200
Subject: [PATCH] Define DT constants in a C header file

Allows writing baremetal programs that can read the correct offsets of
devices or clock frequencies.
---
 dts/.gitignore                    |  2 ++
 dts/Makefile                      | 17 +++++++++++++++++
 ox-plic.dts => dts/lagarto_ox.dts | 18 ++++++++++--------
 dts/lagarto_ox.h                  |  9 +++++++++
 lagarto-ox.nix                    | 22 ++++++++++++++++------
 5 files changed, 54 insertions(+), 14 deletions(-)
 create mode 100644 dts/.gitignore
 create mode 100644 dts/Makefile
 rename ox-plic.dts => dts/lagarto_ox.dts (95%)
 create mode 100644 dts/lagarto_ox.h

diff --git a/dts/.gitignore b/dts/.gitignore
new file mode 100644
index 0000000..2008a4a
--- /dev/null
+++ b/dts/.gitignore
@@ -0,0 +1,2 @@
+*.pp.dts
+*.dtb
diff --git a/dts/Makefile b/dts/Makefile
new file mode 100644
index 0000000..7f7d3be
--- /dev/null
+++ b/dts/Makefile
@@ -0,0 +1,17 @@
+CC?=gcc
+DTC?=dtc
+
+CPPFLAGS=-E -C -P -nostdinc -undef -x assembler-with-cpp
+
+all: lagarto_ox.dtb
+
+clean:
+	rm -f *.pp.dts *.dtb
+
+%.pp.dts: %.dts *.h
+	$(CC) $(CPPFLAGS) $< -o $@
+
+%.dtb: %.pp.dts
+	dtc -O dtb -o $@ $^
+
+.PRECIOUS: %.pp.dts
diff --git a/ox-plic.dts b/dts/lagarto_ox.dts
similarity index 95%
rename from ox-plic.dts
rename to dts/lagarto_ox.dts
index b233d59..5a4776d 100644
--- a/ox-plic.dts
+++ b/dts/lagarto_ox.dts
@@ -1,3 +1,5 @@
+#include "lagarto_ox.h"
+
 /dts-v1/;
 / {
 	#address-cells = <2>;
@@ -19,9 +21,9 @@
 
 		// The RTC timer is clocked at the CPU frequency / 1525, so
 		// around 32786.88 Hz
-		timebase-frequency = <32786>;
+		timebase-frequency = <RTC_CLOCK_FREQUENCY>;
 		CPU0: cpu@0 {
-			clock-frequency = <50000000>; /* 50 MHz */
+			clock-frequency = <CPU_CLOCK_FREQUENCY>; /* 50 MHz */
 			device_type = "cpu";
 			reg = <0>;
 			status = "okay";
@@ -120,14 +122,14 @@
 		 * consoles */
 
 		/* The serial for the kernel console */
-		uart_console: serial@40001000 {
+		uart_console: serial@UART0_ADDR_HEX {
 			compatible = "ns16550";
-			reg = <0x0 0x40001000 0x0 0x1000>;
+			reg = <0x0 UART0_ADDR 0x0 0x1000>;
 			reg-shift = <2>;
 			/* No interrupts for this UART, use console=hvc0 */
 			/* This clock is the SERIAL_CLK */
-			clock-frequency = <50000000>;
-			current-speed = <115200>;
+			clock-frequency = <CPU_CLOCK_FREQUENCY>;
+			current-speed = <UART_SPEED>;
 			status = "okay";
 		};
 		/* The serial for interrupt tests */
@@ -138,8 +140,8 @@
 			/* Output interrupt 1 (the first one) */
 			interrupts = <1>;
 			interrupt-parent = <&PLIC>;
-			clock-frequency = <50000000>;
-			current-speed = <115200>;
+			clock-frequency = <CPU_CLOCK_FREQUENCY>;
+			current-speed = <UART_SPEED>;
 			status = "okay";
 		};
 
diff --git a/dts/lagarto_ox.h b/dts/lagarto_ox.h
new file mode 100644
index 0000000..4a93006
--- /dev/null
+++ b/dts/lagarto_ox.h
@@ -0,0 +1,9 @@
+#define CPU_CLOCK_FREQUENCY	50000000 // 50 MHz
+#define RTC_CLOCK_FREQUENCY	32786
+
+#define UART_SPEED		115200
+#define UART0_ADDR		0x40001000
+#define UART0_ADDR_HEX		  40001000
+
+#define PLIC_ADDR		0x40800000
+#define UART_ADDR		0x40001000
diff --git a/lagarto-ox.nix b/lagarto-ox.nix
index 4505759..01f54f9 100644
--- a/lagarto-ox.nix
+++ b/lagarto-ox.nix
@@ -370,11 +370,21 @@
     #  };
     #}));
 
-    ox-dtb = prev.runCommand "ox.dtb" {
-      dtsFile = ./ox-plic.dts;
-      #dtsFile = ./xavi.dts;
+    ox-dtb = prev.stdenv.mkDerivation rec {
+      name = "ox.dtb";
+      src = ./dts;
+      dontConfigure = true;
       nativeBuildInputs = [ prev.buildPackages.dtc ];
-    } "dtc -O dtb -o $out $dtsFile";
+      buildPhase = ''
+        make lagarto_ox.dtb
+      '';
+      installPhase = ''
+        mkdir $out
+        cp lagarto_ox.* $out
+      '';
+      dontFixup = true;
+      hardeningDisable = [ "all" ];
+    };
 
     #bitstream = "${final.bitstreams}/lagarto-3-ox/gold.bit";
     bitstream = "${final.bitstreams}/lagarto-3-ox/ox_u55c_450d0ff0_fix_delegation_v2.bit";
@@ -448,7 +458,7 @@
       extraMakeFlags = [
         "V=1"
         #"KCPPFLAGS=-DLOG_DEBUG"
-        #"EXT_DTB=${final.ox-dtb}"
+        #"EXT_DTB=${final.ox-dtb}/lagarto_ox.dtb"
       ];
     };
 
@@ -509,7 +519,7 @@
         #"PLATFORM_RISCV_ISA=rv64g" # No compressed instructions
         #"PLATFORM_RISCV_ABI=lp64d"
         "FW_PAYLOAD_PATH=${final.uboot}/u-boot-nodtb.bin"
-        "FW_FDT_PATH=${final.ox-dtb}"
+        "FW_FDT_PATH=${final.ox-dtb}/lagarto_ox.dtb"
 
         # Ensure it doesn't overlap from the 0x80200000 where the kernel will be
         # placed.