[MCU] 为国产芯片增加OpenOCD Flash驱动----以AIC8800为例

le062 2022-2-20 20:08 楼主

一般而言，在上手一个新芯片时，如果其架构已被OpenOCD支持，那么可以直接访问其寄存器及RAM。但对于Flash部分，往往需要写一个几百行的Flash驱动文件。

Flash操作的基本套路

显而易见的，调试器可以控制CPU、可以改写寄存器和RAM，最直接的方式就是通过访问Flash控制器的相关寄存器来完成对Flash的擦除及写入。但在这颗芯片上，原厂并没有提供Flash控制器的资料，而是提供了一个ROM API表，如下：

struct aic8800_rom_falsh_api_t {
    void (*undefined_api_0)(void);
    void (*undefined_api_1)(void);
    uint32_t (*ChipSizeGet)(void);
    void (*ChipErase)(void);
    int32_t (*Erase)(uint32_t addr_4k, uint32_t len);
    int32_t (*Write)(uint32_t addr_256, uint32_t len, uint32_t buf);
    int32_t (*Read)(uint32_t addr_256, uint32_t len, uint32_t buf);
    void (*CacheInvalidAll)(void);
    void (*CacheInvalidRange)(uint32_t addr, uint32_t len);
} aic8800_rom_falsh_api @ 0x00000180UL;

就是说，我们需要让调试器调用这些API来完成对应功能。

构造API调用

需要注意的是这些API是普通的C函数，在调用前，需要配置好传入参数及栈。同时，为了让所运行的程序能自动暂停，也需要增加一个特殊汇编指令 bkpt，完整的汇编代码如下：

    LDR.N R3, [PC, #0x4]    /* 将后面的入口地址载入R3，已知的ROM API最多只需要用到R0-R2*/
    BLX R3                  /* 调用ROM API */
    BKPT #0x0               /* 程序在此处暂停 */
    NOP                     /* 填充 */
    DC32 0x12345678         /* 用于填充ROM API的入口地址 */

部分代码解析

以擦除为例，请看下列代码中的中文注释

static uint32_t romapi_Erase(struct flash_bank *bank, uint32_t addr, uint32_t len)
{
	int retval;
	struct working_area *algorithm;
	struct target *target = bank->target;
	struct aic8800_flash_bank *aic8800_bank = bank->driver_priv;
	struct reg_param reg_params[3];

	/*
		在脚本指定的work-area（即部分SRAM区域）中，分配一块RAM用于放入汇编代码及栈
	*/
	retval = target_alloc_working_area(target, sizeof(struct aic8800_rom_api_call_code_t) + STACK_DEFAULT, &algorithm);
	if (retval != ERROR_OK) {
		LOG_ERROR("Insufficient working area to initialize. You must allocate at least %zdB of working "
			"area in order to use this driver.", sizeof(struct aic8800_rom_api_call_code_t) + STACK_DEFAULT);
		return retval;
	}
	
	/*
		将调用Erase API的汇编代码写入这块SRAM的头部
	*/
	retval = target_write_buffer(target, algorithm->address, sizeof(struct aic8800_rom_api_call_code_t),
									(const uint8_t *)&aic8800_bank->rom_api_call_code[4]);
	if (retval != ERROR_OK) {
		target_free_working_area(target, algorithm);
		return retval;
	}

	/*
		配置R0 R1 SP寄存器
	*/
	init_reg_param(&reg_params[0], "r0", 32, PARAM_IN_OUT);
	init_reg_param(&reg_params[1], "r1", 32, PARAM_OUT);
	init_reg_param(&reg_params[2], "sp", 32, PARAM_OUT);
	buf_set_u32(reg_params[0].value, 0, 32, addr);
	buf_set_u32(reg_params[1].value, 0, 32, len);
	buf_set_u32(reg_params[2].value, 0, 32, algorithm->address + algorithm->size);

	/*
		#define CALL_CODE_BKPT_ADDR(enter_addr)		((enter_addr) + 4)
		调用汇编，指定了汇编代码的入口地址及自动断点地址，并根据擦除块的数量粗略计算了一个超时时间
	*/
	LOG_DEBUG("Running AIC8800 Erase algorithm");
	retval = target_run_algorithm(target, 0, NULL, dimof(reg_params), reg_params,
									algorithm->address, CALL_CODE_BKPT_ADDR(algorithm->address),
									TIMEROUT_ERASE_4K * (len / 4096), &aic8800_bank->armv7m_info);
	if (retval != ERROR_OK) {
		LOG_ERROR("Error executing Erase algorithm");
	}

	/*
		释放资源
	*/
	target_free_working_area(target, algorithm);
	destroy_reg_param(&reg_params[0]);
	destroy_reg_param(&reg_params[1]);
	destroy_reg_param(&reg_params[2]);

	return retval;
}

其他代码及编译过程不再赘述

脚本调用

AIC8800的调试脚本与其他Cortex-M4基本相同，需要修改的有两点：

指定一个RAM区域，用于运行Flash操作代码

$_TARGETNAME configure -work-area-phys 0x00160000 -work-area-size $_WORKAREASIZE -work-area-backup 0

指定Flash起始地址

flash bank $_FLASHNAME aic8800 0x08000000 0 0 0 $_TARGETNAME

测试

运行

.openocd.exe -f .cmsis-dap_v2_aic8800m.cfg
Open On-Chip Debugger 0.11.0+dev-gce5ddd7f7 (2022-02-20-08:04)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : Using CMSIS-DAPv2 interface with VID:PID=0x1209:0x6666, serial=Vllink.Basic.0123456789A
Info : CMSIS-DAP: SWD  supported
Info : CMSIS-DAP: JTAG supported
Info : CMSIS-DAP: SWO-UART supported
Info : CMSIS-DAP: Atomic commands supported
Info : CMSIS-DAP: Test domain timer supported
Info : CMSIS-DAP: FW Version = 0254
Info : CMSIS-DAP: Serial# = Vllink.Basic.0123456789A
Info : CMSIS-DAP: Interface Initialised (SWD)
Info : SWCLK/TCK = 0 SWDIO/TMS = 0 TDI = 0 TDO = 0 nTRST = 0 nRESET = 1
Info : CMSIS-DAP: Interface ready
Info : clock speed 8000 kHz
Info : SWD DPIDR 0x2ba01477
Info : aic8800m.cpu: Cortex-M4 r0p1 processor detected
Info : aic8800m.cpu: target has 2 breakpoints, 1 watchpoints
Info : starting gdb server for aic8800m.cpu on 3333
Info : Listening on port 3333 for gdb connections

连接Telnet 127.0.0.1:4444，执行如下命令完成测试

Open On-Chip Debugger
> halt
target halted due to debug-request, current mode: Thread 
xPSR: 0x21000000 pc: 0x00002272 msp: 0x0019ff88
> flash probe 0
Flash Size = 2048kbytes
flash 'aic8800' found at 0x08000000

> flash write_image erase ./host_wb.bin 0x08000000 bin
Padding image section 0 at 0x08063c18 with 232 bytes (bank write end alignment)
Adding extra erase range, 0x08063d00 .. 0x08063fff
auto erase enabled
wrote 408832 bytes from file ./host_wb.bin in 4.843174s (82.436 KiB/s)

> flash verify_image ./host_wb.bin 0x08000000 bin
Padding image section 0 at 0x08063c18 with 232 bytes (bank write end alignment)
verified 408832 bytes from file ./host_wb.bin in 0.732257s (545.232 KiB/s)

> flash erase_check 0
successfully checked erase state
        #  0: 0x00000000 (0x1000 4kB) not erased
        #  1: 0x00001000 (0x1000 4kB) not erased
        #  2: ...
        ... 
        #  97: ...
        # 98: 0x00062000 (0x1000 4kB) not erased
        # 99: 0x00063000 (0x1000 4kB) not erased
        #511: 0x001ff000 (0x1000 4kB) not erased

> flash erase_sector 0 0 510
erased sectors 0 through 510 on flash bank 0 in 0.679665s

> flash erase_check 0
successfully checked erase state
        #511: 0x001ff000 (0x1000 4kB) not erased

>

总结

在增加Flash驱动后，可以在调试过程中直接一键完成程序的下载，非常方便。

几个链接

要666

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