Steward
分享是一種喜悅、更是一種幸福
掌機 - Gaviar (小志掌機) - 修改OpenSBI
參考資訊：
https://linux-sunxi.org/Allwinner_Nezha
https://github.com/steward-fu/website/releases/tag/gaviar
https://docs.riscv.org/reference/sbi/v3.0/ext-legacy.html
https://github.com/ylyamin/RT-Thread-on-Allwinner-D1H/blob/master/documentation/D1_2_boot_process.md
由於全志針對F133的開機設計流程過於複雜，因此，為了可以更精簡以及方便維護程式碼，司徒特別針對小志掌機修改了一版OpenSBI，修改後的流程如下所示
編譯步驟：
$ cd $ wget https://github.com/steward-fu/website/releases/download/gaviar/thead_toolchain.tar.gz $ tar xvf thead_toolchain.tar.gz $ sudo mv thead /opt $ export PATH=/opt/thead/bin:$PATH $ cd $ wget https://github.com/steward-fu/website/releases/download/gaviar/opensbi_20260906.tar.gz $ tar xvf opensbi_20260906.tar.gz $ cd opensbi $ export PLATFORM=allwinner/f133 $ export CROSS_COMPILE=riscv64-unknown-linux-gnu- $ make distclean $ CONFIG=BROM make $ python3 scripts/gen_checksum.py ./build/platform/allwinner/f133/firmware/fw_jump.bin fw_jump.bin $ dd if=fw_jump.bin of=payload/brom.bin bs=1024 count=32 $ rm -rf fw_jump.bin $ make distclean $ make $ python3 scripts/gen_checksum.py ./build/platform/allwinner/f133/firmware/fw_jump.bin payload/fw_jump.bin $ python3 scripts/gen_checksum.py ./build/platform/allwinner/f133/firmware/fw_payload.bin payload/fw_payload.bin $ sudo dd if=payload/brom.bin of=/dev/sdX bs=1024 seek=8 $ sudo dd if=payload/fw_jump.bin of=/dev/sdX bs=1024 seek=40 $ sudo dd if=dtb of=/dev/sdX bs=1024 seek=300 $ sudo dd if=Image of=/dev/sdX bs=1024 seek=400
由於目前Kernel程式碼尚未完成，因此，司徒使用LED閃爍程式替代，開機後，OpenSBI會跑LED閃爍程式
Baudrate 115200bps
[UART] Gaviar Handheld
[DRAM] ZQ value = 0x2f
[DRAM] get_pmu_exist() = -1
[DRAM] ddr_efuse_type = 0xa
[DRAM] trefi = 7.8ms
[DRAM] single rank and full DQ!
[DRAM] ddr_efuse_type = 0xa
[DRAM] trefi = 7.8ms
[DRAM] rank 0 row = 13
[DRAM] rank 0 bank = 4
[DRAM] rank 0 page size = 2 KB
[DRAM] DRAM BOOT DRIVE INFO: v0.33
[DRAM] DRAM CLK = 528 MHz
[DRAM] DRAM Type = 2 (2:DDR2, 3:DDR3)
[DRAM] DRAMC read ODT off
[DRAM] DRAM ODT off
[DRAM] ddr_efuse_type = 0xa
[DRAM] DRAM SIZE = 64M
[DRAM] dram_tpr4 = 0x0
[DRAM] PLL_DDR_CTRL_REG = 0xf8002b00
[DRAM] DRAM_CLK_REG = 0xc0000000
[DRAM] MR2 = 0x0
[DRAM] DRAM simple test OK
[eMMC] MicroSD size = 59688MB
[eMMC] Copy DTB to 0x41500000 (size = 65536)...
[eMMC] Copy Kernel to 0x40008000 (size = 8388608)...
[eMMC] Copy OpenSBI to 0x41000000 (size = 262144)...
Welcome to Gaviar handheld
OpenSBI v1.3
____ _____ ____ _____
/ __ \ / ____| _ \_ _|
| | | |_ __ ___ _ __ | (___ | |_) || |
| | | | '_ \ / _ \ '_ \ \___ \| _ < | |
| |__| | |_) | __/ | | |____) | |_) || |_
\____/| .__/ \___|_| |_|_____/|____/_____|
| |
|_|
Platform Name : Allwinner F133
Platform Features : medeleg
Platform HART Count : 1
Platform IPI Device : ---
Platform Timer Device : --- @ 0Hz
Platform Console Device : f133_uart
Platform HSM Device : ---
Platform PMU Device : ---
Platform Reboot Device : ---
Platform Shutdown Device : ---
Platform Suspend Device : ---
Platform CPPC Device : ---
Firmware Base : 0x41000000
Firmware Size : 194 KB
Firmware RW Offset : 0x20000
Firmware RW Size : 66 KB
Firmware Heap Offset : 0x28000
Firmware Heap Size : 34 KB (total), 2 KB (reserved), 8 KB (used), 23 KB (free)
Firmware Scratch Size : 4096 B (total), 728 B (used), 3368 B (free)
Runtime SBI Version : 1.0
Domain0 Name : root
Domain0 Boot HART : 0
Domain0 HARTs : 0*
Domain0 Region00 : 0x0000000041000000-0x000000004101ffff M: (R,X) S/U: ()
Domain0 Region01 : 0x0000000041020000-0x000000004103ffff M: (R,W) S/U: ()
Domain0 Region02 : 0x0000000000000000-0xffffffffffffffff M: () S/U: (R,W,X)
Domain0 Next Address : 0x0000000040008000
Domain0 Next Arg1 : 0x0000000041500000
Domain0 Next Mode : S-mode
Domain0 SysReset : yes
Domain0 SysSuspend : yes
Boot HART ID : 0
Boot HART Domain : root
Boot HART Priv Version : v1.11
Boot HART Base ISA : rv64imafdcvx
Boot HART ISA Extensions : zicntr
Boot HART PMP Count : 8
Boot HART PMP Granularity : 2048
Boot HART PMP Address Bits: 38
Boot HART MHPM Count : 0
Boot HART MHPM Mask : 0x0
Boot HART MIDELEG : 0x0000000000000222
Boot HART MEDELEG : 0x000000000000b109
Jump to kernel (0x40008000) ...
司徒列出幫小志掌機修改的部份
為何RISC-V需要有這些模式呢？可以從下圖得知，Linux/OS一般跑在S-Mode，但是當需要控制底層時，就需要切換M-Mode，這也是SBI介面的由來，當然，如果不用Linux/OS，就可以自己實做這一部份
為了讓OpenSBI具有開機執行的能力，司徒小改了一下fw_base.S，在程式進入點_gaviar加入判斷程式，如果是從0x20000的位址執行，則執行第一次初始化的動作，包含初始化UART、DRAM、MMC等，並且加載OpenSBI、Kernel、DTB到DRAM，至於為何是判斷位址0x20000呢？這是因為F133 BROM一上電後，會先從MicroSD 8KB位址處加載32KB程式到RAM 0x20000並且執行，所以司徒在0x20000處做標記(F133_TAG)，接著等第二次執行時，這時候位址已經改成從0x41000000執行，所以就會直接跑_start的程式，因此我們需要兩份fw_jump.bin，一份是給0x20000用的(32KB)，另一份則是完整的fw_jump.bin，司徒使用CONFIG=brom make用來編譯0x20000的fw_jump.bin，詳細的執行流程如下所示：
預計的MicroSD Layout
更新檔案的方式
$ sudo dd if=fw_jump.bin of=/dev/sdX bs=1024 seek=8 $ sudo dd if=fw_jump.bin of=/dev/sdX bs=1024 seek=40 $ sudo dd if=dtb of=/dev/sdX bs=1024 seek=300 $ sudo dd if=Image of=/dev/sdX bs=1024 seek=400
由於目前司徒先使用LED閃爍程式替代Kernel，那是否代表可以修改這個LED閃爍程式來呼叫SBI Interface呢？答案肯定是可以的，程式碼如下：
.global _start
.text
.long 0x05c0006f
.byte 'e','G','O','N','.','B','T','0'
.long 0x5f0a6c39
.long 0x8000
.long 0, 0
.long 0, 0, 0, 0, 0, 0, 0, 0
.long 0, 0, 0, 0, 0, 0, 0, 0
_start:
la a0, msg
call sbi_puts
1:
j 1b
sbi_puts:
mv t0, a0
1:
lbu a0, 0(t0)
beqz a0, 2f
li a7, 1
ecall
addi t0, t0, 1
j 1b
2:
ret
msg: .asciz "\n\nHello, world!\n"
.end
編譯、燒錄
$ riscv64-unknown-linux-gnu-as -o main.o main.s $ riscv64-unknown-linux-gnu-ld -T main.ld -o main.elf main.o $ riscv64-unknown-linux-gnu-objcopy -O binary main.elf tmp.bin $ python3 gen_checksum.py tmp.bin main.bin $ sudo dd if=main.bin of=/dev/sdb bs=1024 seek=400
開機後就可以從UART看到Hello, world!字串，如果想從屏幕上印出字串，只要修改lib/sbi/sbi_ecall_legacy.c，將#if 0改成#if 1後，重新編譯燒錄即可
static int sbi_ecall_legacy_handler(unsigned long extid, unsigned long funcid,
const struct sbi_trap_regs *regs,
unsigned long *out_val,
struct sbi_trap_info *out_trap)
{
int ret = 0;
struct sbi_tlb_info tlb_info;
u32 source_hart = current_hartid();
ulong hmask = 0;
switch (extid) {
case SBI_EXT_0_1_SET_TIMER:
#if __riscv_xlen == 32
sbi_timer_event_start((((u64)regs->a1 << 32) | (u64)regs->a0));
#else
sbi_timer_event_start((u64)regs->a0);
#endif
break;
case SBI_EXT_0_1_CONSOLE_PUTCHAR:
sbi_putc(regs->a0);
#if 0
/* Added by Steward for Gaviar handheld */
void f133_slcd_putc(char ch);
f133_slcd_putc(regs->a0);
#endf
break;
Legacy SBI Interface有如下幾個Function，上面的那個main.s範例就是使用EID 0x01的sbi_console_putchar()印出字串，藉由上面的main.s範例，讓我們可以更了解SBI Interface的運作原理
呼叫的流程如下：
Memory Layout如下：
Device Tree保留這些區域避免被覆蓋
memory@40000000 {
device_type = "memory";
reg = <0x0 0x40000000 0x0 0x04000000>; /* 64 MB */
};
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
opensbi_reserved: opensbi@43e00000 {
reg = <0x0 0x43e00000 0x0 0x00080000>; /* 512 KiB */
no-map;
};
dtb_reserved: dtb@43d00000 {
reg = <0x0 0x43d00000 0x0 0x00010000>; /* 64 KiB */
no-map;
};
};
開機後的Log
[ 0.000000] Linux version 5.4.61 (steward@debian) (riscv64-unknown-linux-gnu-gcc (C-SKY RISCV Tools V1.8.4 B20200702) 8.1.0, GNU ld (GNU Binutils) 2.32) #1 PREEMPT Fri Sep 11 07:05:18 CST 2026 [ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '') [ 0.000000] printk: bootconsole [sbi0] enabled [ 0.000000] cma: Reserved 16 MiB at 0x0000000042c00000 [ 0.000000] Zone ranges: [ 0.000000] DMA32 [mem 0x0000000040000000-0x0000000043ffffff] [ 0.000000] Normal empty [ 0.000000] Movable zone start for each node [ 0.000000] Early memory node ranges [ 0.000000] node 0: [mem 0x0000000040000000-0x0000000043cfffff] [ 0.000000] node 0: [mem 0x0000000043d10000-0x0000000043dfffff] [ 0.000000] node 0: [mem 0x0000000043e80000-0x0000000043ffffff] [ 0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x0000000043ffffff]