Foreword:
In this article, we briefly introduce how to detect specific hardware devices through the I2C protocol on the Allwinner Android platform. It will start with the confirmation of hardware connection, then introduce the necessary system configuration, then follow the detailed settings according to the data sheet, and finally implement a simple I2C driver to identify the DMT C0A9 encryption chip.
Allwinner Platform A40I: Debugging Notes on I2C Communication Problems
- Confirm the connection interface of hardware I2C2
TWI2_SCK=PB20
TWI2_SDA=PB21
- Confirm the configuration of sys_config.fex
[twi2]
twi2_used = 1
twi2_scl = port:PB20<2><default><default><default>
twi2_sda = port:PB21<2><default><default><default>
- Confirm datasheet
TWI2_SCK=PB20_SELECT的010
TWI2_SDA=PB21_SELECT的010
-
Confirm the dts file
If there is no twi2, you need to add it, and add the corresponding driver configuration
The dts configuration is written differently, otherwise it will cause mismatching To be compatible so that the probe function cannot be executed, the current kernel version needs to remove @38.twi2: twi@0x01c2b400 { interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>; status = "okay"; dmt_c0a9 { //dmt_c0a9@38 { compatible = "dmt,dmt_c0a9"; reg = <0x38>; status = "okay"; }; }; -
Confirm whether the files compiled by dts are compiled to
xxxx\boot\dts.xxx.dtb.dts
twi2: twi@0x01c2b400 { interrupts = <0 4 4>; status = "okay"; dmt_c0a9 { compatible = "dmt,dmt_c0a9"; reg = <0x38>; status = "okay"; }; }; -
Confirm that the I2C function is configured successfully
a40-p1:/proc/sys/debug/sunxi_pinctrl # cat sunxi_pin_configure pin[PB20] funciton: 2 pin[PB20] data: 0 pin[PB20] dlevel: 1 pin[PB20] pull: 0 a40-p1:/proc/sys/debug/sunxi_pinctrl # echo PB21 > sunxi_pin a40-p1:/proc/sys/debug/sunxi_pinctrl # cat sunxi_pin_configure pin[PB21] funciton: 2 pin[PB21] data: 0 pin[PB21] dlevel: 1 pin[PB21] pull: 0 -
Confirm that the system can detect the hardware I2C address
a40-p1:/proc/sys/debug/sunxi_pinctrl # i2cdetect -ya 2 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- 38 -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- -- -
Write a simple driver c0a9
//1.测试读写
static int dmt_c0a9_read(struct dmt_c0a9_dev *dmt_c0a9, u8 *buf, u32 len)
{
int ret;
printk(KERN_INFO "Entering: %s\n", __func__);
// Reading data using i2c_master_recv
ret = i2c_master_recv(dmt_c0a9->client, buf, len);
if (ret < 0)
{
dev_err(dmt_c0a9->dev, "i2c_master_recv failed with ret = %d\n", ret);
}
else if (ret != len)
{
dev_err(dmt_c0a9->dev, "Expected %d bytes, received %d bytes\n", len, ret);
}
printk(KERN_INFO "Exiting: %s with ret = %d\n", __func__, ret);
return ret;
}
static int dmt_c0a9_write(struct dmt_c0a9_dev *dmt_c0a9, u8 *buf, u32 len)
{
int ret;
printk(KERN_INFO "Entering: %s\n", __func__);
// Writing data using i2c_master_send
ret = i2c_master_send(dmt_c0a9->client, buf, len);
if (ret < 0)
{
dev_err(dmt_c0a9->dev, "i2c_master_send failed with ret = %d\n", ret);
}
else if (ret != len)
{
dev_err(dmt_c0a9->dev, "Expected %d bytes to be sent, actually sent %d bytes\n", len, ret);
}
printk(KERN_INFO "Exiting: %s with ret = %d\n", __func__, ret);
return ret;
}
static int dmt_c0a9_test(struct dmt_c0a9_dev *dmt_c0a9)
{
int ret;
printk(KERN_INFO "Entering: %s\n", __func__);
// Writing data to I2C device
ret = dmt_c0a9_write(dmt_c0a9, txbuf, 32);
if (ret)
{
dev_err(dmt_c0a9->dev, "Write operation failed with ret = %d\n", ret);
return ret;
}
// Reading data from I2C device
ret = dmt_c0a9_read(dmt_c0a9, rxbuf, 32);
if (ret)
{
dev_err(dmt_c0a9->dev, "Read operation failed with ret = %d\n", ret);
return ret;
}
// Data processing and verification can be done here
printk(KERN_INFO "Exiting: %s with ret = %d\n", __func__, ret);
return 0;
}
//2.测试c0a9的驱动能够探测到I2C地址0
static int dmt_c0a9_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
int ret;
u8 dummy_data = 0;
printk(KERN_INFO "Entering: %s\n", __func__);
// 尝试向设备发送一个字节的数据以检测其存在性
ret = i2c_master_send(client, &dummy_data, 1);
if (ret == 1) {
printk(KERN_INFO "Device found at address 0x38\n");
return 0; // Device exists
} else {
printk(KERN_INFO "No device found at address 0x38\n");
//未检测到DMT C0A9设备 - 触发内核重启
panic("DMT C0A9 not detected - triggering kernel panic");
return -ENODEV; // Device does not exist
}
}
Summarize:
Through the introduction of this article, I learned the entire process of detecting I2C devices on the Allwinner platform and controlling them through drivers.