Add `litex` target

Use configuration from the `csr.h` file
generated dynamically when building a LiteX platform.

src/main/c/emulator/makefile

@@ -18,6 +18,11 @@ sim: all
 qemu: CFLAGS += -DQEMU
 qemu: all
 
+litex: CFLAGS += -DLITEX -I${LITEX_BASE}/software/include
+litex: | check_litex_base all
+check_litex_base:
+	@[ "${LITEX_BASE}" ] || ( echo ">> LITEX_BASE is not set"; exit 1 )
+
 include ${STANDALONE}/common/riscv64-unknown-elf.mk
 include ${STANDALONE}/common/standalone.mk
 

src/main/c/emulator/src/hal.c

@@ -144,5 +144,76 @@ void halInit(){
 #endif
 
 
+#ifdef LITEX
+
+// this is copied from LiteX <hw/common.h>
+#define CSR_ACCESSORS_DEFINED
+static inline void csr_writeb(uint8_t value, unsigned long addr)
+{
+	*((volatile uint8_t *)addr) = value;
+}
+
+static inline uint8_t csr_readb(unsigned long addr)
+{
+	return *(volatile uint8_t *)addr;
+}
+
+static inline void csr_writew(uint16_t value, unsigned long addr)
+{
+	*((volatile uint16_t *)addr) = value;
+}
+
+static inline uint16_t csr_readw(unsigned long addr)
+{
+	return *(volatile uint16_t *)addr;
+}
+
+static inline void csr_writel(uint32_t value, unsigned long addr)
+{
+	*((volatile uint32_t *)addr) = value;
+}
+
+static inline uint32_t csr_readl(unsigned long addr)
+{
+	return *(volatile uint32_t *)addr;
+}
+
+// this is a file generated by LiteX
+#include <generated/csr.h>
+
+#if !defined(CSR_UART_BASE) || !defined(CSR_CPU_BASE)
+	#error LiteX configuration with uart and cpu_timer is required.
+#endif
+
+void stopSim(){
+	while(1);
+}
+
+void putC(char ch){
+	uart_rxtx_write(ch);
+}
+
+int32_t getC(){
+	return uart_rxempty_read()
+		? -1
+		: uart_rxtx_read();
+}
+
+uint32_t rdtime(){
+ 	return (uint32_t)cpu_timer_time_read();
+}
+
+uint32_t rdtimeh(){
+ 	return (uint32_t)(cpu_timer_time_read() >> 32);
+}
+
+void setMachineTimerCmp(uint32_t low, uint32_t high){
+	cpu_timer_time_cmp_write((((unsigned long long int)high) << 32) | low);
+}
+
+void halInit(){
+}
+
+#endif
 
 

src/main/c/emulator/src/main.c

@@ -161,7 +161,7 @@ void trap(){
 #ifdef SIM
 			uint32_t instruction = csr_read(mbadaddr);
 #endif
-#ifdef QEMU
+#if defined(QEMU) || defined(LITEX)
 			uint32_t instruction = 0;
 			uint32_t i;
 			if (mepc & 2) {