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Driver: ACC¶

1 功能概述¶

外设模块ACC模块主要用于计算两个32位无符号数相乘，并将其值累加存储起来，用于加速向量点积操作，同时也可当作硬件除法器。该sample演示了外设模块ACC的点乘运算和除法运算。

2 环境要求¶

PAN1080 EVB一块
Micro USB线一条（用于供电和查看串口打印Log）
硬件接线：
- 使用USB线，将PC USB与EVB MicroUSB（USB->UART）相连
- 使用杜邦线将EVB上的:
  - UART1 TX与P06相连
  - UART1 RX与P07相连
PC软件: 串口调试助手（UartAssist）或终端工具（SecureCRT），波特率921600

3 编译和烧录¶

项目位置：zephyr\samples_panchip\drivers\acc

目前可使用ZAL工具或quick build脚本进行编译和下载。

脚本位置：quick_build_samples\drivers\acc.bat

打开脚本后默认会编译项目，编译完成时，可输入字符进行后续下载等操作:

Input the keyword to continue:
  'b' build                         编译项目
  'r' make clean and rebuild        重新编译项目
  'f' flash download                下载
  'e' erase chip                    擦除芯片
  'o' open project by VS Code       打开 `VS Code`，可查看源码，执行编译下载等
  others exit                       退出
wait input:

4 演示说明¶

4.1点乘运算¶

设置了两个包含8个固定元素的向量。

static uint32_t mult_left[MULT_BUFFER_SIZE] = { /*向量1元素*/
	0x1122, 0x2233, 0x3344, 0x3,
	0x4, 0x5, 0x6, 0x1234
};
static uint32_t mult_right[MULT_BUFFER_SIZE] = { /*向量2元素*/
	0, 1, 2, 3, 4, 5, 6, 7
};

启动ACC乘法运算，并获取结果。

ret = acc_start_multiplier(acc_dev, &acc_mult_cfg); /*启动acc模块点乘运算*/
if (ret != 0) {
	LOG_INF("acc start multiplier failed with code %d", ret);
}

ret = acc_get_value(acc_dev, &acc_mult_cfg); /*获取运算结果*/
if (ret != 0) {
	LOG_INF("acc get value failed with code %d", ret);
}

for (uint8_t i = 0; i < RESULT_BUFFER_SIZE; i++) { /*缓存运算结果*/
	result_buffer[i] = acc_mult_cfg.buffer[i];
}

对比ACC模块计算值与事先已验证过的正确值，判断ACC模块点乘运算功能是否正常，数值一致打印success，否则打印 “[数值_sw] should equal to [数值_hw] ”。

4.2 除法运算¶

从向量中选取一组数值作为除数与被除数，启动ACC除法运算，并获取结果。

ret = acc_start_divider(acc_dev, &acc_div_cfg); /*启动acc模块除法运算*/
if (ret != 0) {
	LOG_INF("acc start divider failed with code %d", ret);
}

result = acc_div_cfg.buffer[0];	/*获取运算结果*/

使用除法器中运算使用的除数与被除数通过软件计算方式计算结果，对比软件结果与除法器结果，数值一致打印divider success，否则打印“[数值_sw] != [数值_hw]”。
```
result_sw = acc_div_cfg.divisor / acc_div_cfg.dividend; /*软件除法运算*/

if (result != result_sw) {	/*对比结果*/
	LOG_INF("[%08x] != [%08x]", result, result_sw);
}
```

5 开发说明¶

5.1 启用ACC模块¶

在prj.conf文件中添加“CONFIG_ACC=y”启用ACC模块。

CONFIG_ACC=y

5.2 初始化ACC¶

int ret;
const struct device *acc_dev;

acc_dev = device_get_binding(DT_LABEL(DT_INST(0, panchip_pan_acc))); /*获取acc设备*/
if (!acc_dev) {
    LOG_INF("Cannot get ACC device\n");
}

ret = acc_set_up(acc_dev, acc_cfg);	/*初始化acc模块*/
if (ret != 0) {
    LOG_INF("Setting up acc config failed with code %d", ret);
}

其中acc_cfg数据结构及参数含义如下

/** @brief Structure with generic accumulator features.
 *
 * @param  operate_mode operate mode select(multiplier or divider)
 * @param  first_multiplier first multiplier data
 * @param  sec_multiplier second multiplier data
 * @param  divisor divisor value
 * @param  dividend dividend value
 * @param  number_words The multiplier calculates the number of polls
 * @param  cycle: The multiplier reserves the computation period
 * @param  buffer: result buffer
 */
struct acc_config_info {
	uint8_t operate_mode;
	uint32_t *first_multiplier;
	uint32_t *sec_multiplier;
	uint32_t divisor;
	uint32_t dividend;
	uint8_t number_words;
	uint8_t calc_cycle;
	uint32_t buffer[16];
};

5.3 ACC API接口¶

接口总览

__subsystem struct acc_driver_api {
	acc_api_set_up set_up;
	acc_api_set_int enable_int;
	acc_api_start_multiplier start_multiplier;
	acc_api_get_multiplier_value get_value;
	acc_api_start_divider start_divider;
};

acc初始化模块配置

/**
 * @brief  This function is used to setup acc device
 * @param  dev Pointer to the device structure for the driver instance.
 * @param  acc_cfg Pointer to acc configuration.
 * @retval 0       On success.
 * @retval -EINVAL If a parameter with an invalid value has been provided.
 */
__syscall int acc_set_up(const struct device *dev,
			 const struct acc_config_info *acc_cfg);

acc中断初始化

/**
 * @brief  This function is used to enable acc interrupt
 * @param  dev Pointer to the device structure for the driver instance.
 * @param  enable_state interrupt enable or not.
 * @retval 0       On success.
 * @retval -EINVAL If a parameter with an invalid value has been provided.
 */
__syscall void acc_enable_int(const struct device *dev, bool enable_state);

acc启动乘法运算

/**
 * @brief  This function is used to start multiplier
 * @param  dev Pointer to the device structure for the driver instance.
 * @param  acc_cfg Pointer to acc configuration.
 * @retval 0       On success.
 * @retval -EINVAL If a parameter with an invalid value has been provided.
 */
__syscall int acc_start_multiplier(const struct device *dev,
				   const struct acc_config_info *acc_cfg);

acc获取运算结果

/**
 * @brief  This function is used to get multiplier result
 * @param  dev Pointer to the device structure for the driver instance.
 * @param  acc_cfg Pointer to acc configuration.
 * @retval 0       On success.
 * @retval -EINVAL If a parameter with an invalid value has been provided.
 */
__syscall int acc_get_value(const struct device *dev,
			    const struct acc_config_info *acc_cfg);

acc启动除法运算

/**
 * @brief  This function is used to start divider
 * @param  dev Pointer to the device structure for the driver instance.
 * @param  acc_cfg Pointer to acc configuration.
 * @retval 0       On success.
 * @retval -EINVAL If a parameter with an invalid value has been provided.
 */
__syscall int acc_start_divider(const struct device *dev,
				const struct acc_config_info *acc_cfg);