Add Linux loader

This privdes just enough firmware to load Linux. The loader is linked to
run from the aliased BRAM address. This means you should configure your
SoC with BRAM (ie, don't pass --no_bram).

It can load a raw kernel (vmlinux.bin) or a wrapper that embeds the
device tree (dtbImage.microwatt).

The printf comes from https://github.com/mpredfearn/simple-printf

 1. Build Linux for microwatt
  objcopy -O binary microwatt/vmlinux vmlinux.bin

 2. Build a dtb

 3. Set MW_DEBUG to point to a copy of mw_debug and type `make load` to
    load the loader into BRAM.

 4. Press 'RESET'

 5. Follow the instructions:

	Microwatt Loader (Jun 22 2020 16:44:59

	Load binaries into SDRAM and select option to start:

	vmlinux.bin and dtb:
	 mw_debug -b jtag stop load vmlinux.bin load microwatt.dtb 0x1000000 start
	 press 'l' to start'

	dtbImage.microwatt:
	 mw_debug -b jtag stop load dtbImage.microwatt 0x500000 start
	 press 'w' to start'

	Flash:
	 To boot a binary from flash, write it to 0000000000300000
	 press 'f' to start'

If you want to test other software, such as MicroPython, you can also
load it to the start of SDRAM and the loader will jump to it with 'l'.

Signed-off-by: Joel Stanley <[email protected]>

.gitignore

@@ -3,10 +3,19 @@
 *.cf
 *.s
 *_tb
+*.swp
 main_ram.bin
 tests/*/*.bin
 tests/*/*.hex
 tests/*/*.elf
 TAGS
 litedram/build/*
 obj_dir/*
+tags
+scripts/mw_debug/mw_debug
+loader/loader.bin
+loader/loader.hex
+loader/loader.elf
+loader/powerpc.lds
+*.swn
+*.swo

loader/Makefile

@@ -0,0 +1,64 @@
+ARCH = $(shell uname -m)
+ifneq ("$(ARCH)", "ppc64")
+ifneq ("$(ARCH)", "ppc64le")
+	CROSS_COMPILE ?= powerpc64le-linux-gnu-
+endif
+endif
+
+PYTHON3 ?= python3
+MW_DEBUG ?= mw_debug
+BRAM_ADDRESS ?= 0x80000000
+
+# Use make V=1 for a verbose build.
+ifndef V
+        Q_CC=     @echo '      [CC] ' $@;
+        Q_LINK=   @echo '    [LINK] ' $@;
+        Q_OBJCOPY=@echo ' [OBJCOPY] ' $@;
+        Q_PYTHON= @echo '  [PYTHON] ' $@;
+endif
+
+CC = $(CROSS_COMPILE)gcc
+LD = $(CROSS_COMPILE)ld
+OBJCOPY = $(CROSS_COMPILE)objcopy
+
+CFLAGS = -Os -g -Wall -std=c99 -msoft-float -mno-string -mno-multiple \
+	 -mno-vsx -mno-altivec -mlittle-endian -fno-stack-protector \
+	 -mstrict-align -ffreestanding -nostdinc -flto \
+	 -Ilibc/include/ -I../include -isystem $(shell $(CC) -print-file-name=include) \
+	 -D__USE_LIBC
+ASFLAGS = $(CFLAGS)
+LDFLAGS = -T powerpc.lds -static -nostdlib -Wl,--gc-sections -Wl,--build-id=none
+
+LIBC_SRC := libc/src/isdigit.c libc/src/memcmp.c libc/src/strcat.c \
+	libc/src/strncasecmp.c libc/src/strtok.c libc/src/vsnprintf.c \
+	libc/src/isprint.c libc/src/memcpy.c libc/src/strchr.c libc/src/strncmp.c \
+	libc/src/strtol.c libc/src/isspace.c libc/src/memmove.c libc/src/strcmp.c \
+	libc/src/strncpy.c libc/src/strtoul.c libc/src/isxdigit.c libc/src/memset.c \
+	libc/src/strcpy.c libc/src/strrchr.c libc/src/tolower.c libc/src/memchr.c \
+	libc/src/strcasecmp.c libc/src/strlen.c libc/src/strstr.c libc/src/toupper.c
+LIBC_OBJ := $(LIBC_SRC:.c=.o)
+
+COMPILE.c = $(Q_CC)$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c
+COMPILE.S = $(Q_CC)$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c
+
+all: loader.hex
+
+load: loader.bin
+	$(MW_DEBUG) -b jtag load $^ $(BRAM_ADDRESS)
+
+%.lds : %.lds.S
+	$(Q_CC)$(CC) -I../include -P -E $< -o $@
+
+loader.elf: loader.o head.o ../lib/console.o $(LIBC_OBJ) | powerpc.lds
+	$(Q_LINK)$(CC) $(LDFLAGS) -o $@ $^
+	@size $@
+
+loader.bin: loader.elf
+	$(Q_OBJCOPY)$(OBJCOPY) -O binary $^ $@
+
+loader.hex: loader.bin
+	$(Q_PYTHON)$(PYTHON3) ../scripts/bin2hex.py $^ > $@
+
+.PHONY:
+clean:
+	@rm -f *.o $(LIBC_OBJ) ../lib/console.o loader.elf loader.bin loader.hex powerpc.lds

loader/head.S

@@ -0,0 +1,38 @@
+/* Copyright 2020 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <microwatt_soc.h>
+
+#define STACK_TOP (BRAM_BASE + 0x3000)
+
+/* Load an immediate 64-bit value into a register */
+#define LOAD_IMM64(r, e)			\
+	lis     r,(e)@highest;			\
+	ori     r,r,(e)@higher;			\
+	rldicr  r,r, 32, 31;			\
+	oris    r,r, (e)@h;			\
+	ori     r,r, (e)@l;
+
+	.section ".head","ax"
+
+.global start
+start:
+	/* setup stack */
+	LOAD_IMM64(%r1, STACK_TOP - 0x100)
+	LOAD_IMM64(%r12, main)
+	mtctr	%r12,
+	bctrl
+	b .

loader/loader.c

@@ -0,0 +1,161 @@
+#include <stdint.h>
+#include <errno.h>
+#include <string.h>
+#include <stdbool.h>
+#include "stdio.h"
+
+#include "io.h"
+#include "microwatt_soc.h"
+#include "console.h"
+#include "elf64.h"
+
+#define DTB_ADDR	0x01000000UL
+#define DTBIMAGE_ADDR 	0x00500000UL
+
+#ifdef DEBUG
+#define debug(...) printf(__VA_ARGS__)
+#else
+#define debug(...) do {} while(0)
+#endif
+
+int _printf(const char *fmt, ...)
+{
+        int count;
+        char buffer[128];
+        va_list ap;
+
+        va_start(ap, fmt);
+        count = vsnprintf(buffer, sizeof(buffer), fmt, ap);
+        va_end(ap);
+        puts(buffer);
+        return count;
+}
+
+static inline void flush_cpu_icache(void)
+{
+	__asm__ volatile ("icbi 0,0; isync" : : : "memory");
+}
+
+static void print_hex(unsigned long val)
+{
+	int i, nibbles = sizeof(val)*2;
+	char buf[sizeof(val)*2+1];
+
+	for (i = nibbles-1;  i >= 0;  i--) {
+		buf[i] = (val & 0xf) + '0';
+		if (buf[i] > '9')
+			buf[i] += ('a'-'0'-10);
+		val >>= 4;
+	}
+	buf[nibbles] = '\0';
+	puts(buf);
+}
+
+static void fl_read(void *dst, uint32_t offset, uint32_t size)
+{
+	memcpy(dst, (void *)(unsigned long)(SPI_FLASH_BASE + offset), size);
+}
+
+static unsigned long boot_flash(unsigned int offset)
+{
+	Elf64_Ehdr ehdr;
+	Elf64_Phdr ph;
+	unsigned int i, poff, size, off;
+	void *addr;
+
+	fl_read(&ehdr, offset, sizeof(ehdr));
+	if (!IS_ELF(ehdr) || ehdr.e_ident[EI_CLASS] != ELFCLASS64) {
+		puts("Doesn't look like an elf64\n");
+		return -1UL;
+	}
+	if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB ||
+	    ehdr.e_machine != EM_PPC64) {
+		puts("Not a ppc64le binary\n");
+		return -1UL;
+	}
+
+	poff = offset + ehdr.e_phoff;
+	for (i = 0; i < ehdr.e_phnum; i++) {
+		fl_read(&ph, poff, sizeof(ph));
+		if (ph.p_type != PT_LOAD)
+			continue;
+
+		/* XXX Add bound checking ! */
+		size = ph.p_filesz;
+		addr = (void *)ph.p_vaddr;
+		off  = offset + ph.p_offset;
+		debug("Copy segment %d (0x%x bytes) to %p\n", i, size, addr);
+		fl_read(addr, off, size);
+		poff += ehdr.e_phentsize;
+	}
+
+	if (poff == offset + ehdr.e_phoff) {
+		puts("Did not find any loadable sections\n");
+		return -1UL;
+	}
+
+	debug("Found entry point: %x\n", ehdr.e_entry);
+
+	flush_cpu_icache();
+	return ehdr.e_entry;
+}
+
+int main(void)
+{
+	unsigned long fl_off = 0;
+	potato_uart_init();
+	unsigned long payload, dtb;
+	void __attribute__((noreturn)) (*enter_kernel)(unsigned long fdt,
+			     unsigned long entry,
+			     unsigned long of);
+
+
+	puts("\nMicrowatt Loader ("__DATE__" "__TIME__"\n\n");
+
+	writeq(SYS_REG_CTRL_DRAM_AT_0, SYSCON_BASE + SYS_REG_CTRL);
+	flush_cpu_icache();
+
+	puts("Load binaries into SDRAM and select option to start:\n\n");
+	puts("vmlinux.bin and dtb:\n");
+	puts(" mw_debug -b jtag stop load vmlinux.bin load microwatt.dtb 0x1000000 start\n");
+	puts(" press 'l' to start'\n\n");
+
+	puts("dtbImage.microwatt:\n");
+	puts(" mw_debug -b jtag stop load dtbImage.microwatt 0x500000 start\n");
+	puts(" press 'w' to start'\n\n");
+
+	if (readq(SYSCON_BASE + SYS_REG_INFO) & SYS_REG_INFO_HAS_SPI_FLASH) {
+		unsigned long val = readq(SYSCON_BASE + SYS_REG_SPI_INFO);
+		fl_off = val & SYS_REG_SPI_INFO_FLASH_OFF_MASK;
+
+		puts("Flash:\n");
+		puts(" To boot a binary from flash, write it to "); print_hex(fl_off); puts("\n");
+		puts(" press 'f' to start'\n\n");
+	}
+
+	while (1) {
+		switch (getchar()) {
+		case 'l':
+			payload = 0;
+			dtb = DTB_ADDR;
+			goto load;
+		case 'w':
+			payload = DTBIMAGE_ADDR;
+			goto load;
+		case 'f':
+			payload = boot_flash(fl_off);
+			if (payload == -1UL)
+				continue;
+			goto load;
+		default:
+			continue;
+		}
+	}
+
+load:
+	puts("Entering payload at "); print_hex(payload); puts("...\n");
+
+	enter_kernel = (void *)payload;
+
+	enter_kernel(dtb, 0, 0);
+}

loader/powerpc.lds.S

@@ -0,0 +1,20 @@
+#include <microwatt_soc.h>
+
+#define BASE_ADDR	BRAM_BASE
+
+SECTIONS
+{
+	. = BASE_ADDR;
+	.head : {
+		KEEP(*(.head))
+	}
+
+	.text : { *(.text*) *(.sfpr) *(.rodata*) }
+	.data : { *(.data*) }
+	.bss : { *(.bss*) }
+
+	/DISCARD/ : {
+                *(.note.*)
+                *(.comment)
+        }
+}