I2C_RX_FIFO
reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_RX_FIFO);
i2c_readsl(i2c_dev, buf, I2C_RX_FIFO, words_to_transfer);
val = i2c_readl(i2c_dev, I2C_RX_FIFO);