How to accessing I2C on dram_init

Yocto
1

We would like to access the i2c from the ‘dram_init(void)’ function in ‘arch/arm/mach-mediatek/mt8188/init.c’ file to set the dram size based on value read with i2c rather than from the device tree.

I have tried the following I2C API functions:

int read_stm32_reg(void) {

u8 bus_num = 3;
u8 chip_addr = 0x40;
u8 reg_addr = 0xf0;

struct udevice *dev;
int ret;
char data[1];

ret = i2c_get_chip_for_busnum(bus_num, chip_addr, reg_addr, &dev);
if (ret) {
    printf("Error getting chip: %d\n", ret);
    return;
}

ret = dm_i2c_reg_read(dev, reg_addr);
if (ret) {
    printf("Error reading from I2C device: %d\n", ret);
    return;
}

printf("Read data from register: %02x\n", data[0]);

return 0;

}

however I am getting an error on u-boot log:

CPU: MediaTek MT8390
DRAM: Error getting chip: -19
4 GiB
…

Can this i2c driver be used for it? Is it even possible to make it work that early in the boot process?

2

Usually developer uses board detection function to apply dram size in advance.

If you want to use dynamic dram detection via I2C, you might be able to call i2c_init_all() “ref: common/board_f.c”
during board init before DM (driver model) driver bring up.
However, MediaTek didn’t tested such scenario, you could try it.