On 04/03/2018 05:39 PM, Wolfram Sang wrote: > >> +#define STM32F7_I2C_DMA_LEN_MIN 0x1 > ... > >> + if (i2c_dev->dma && f7_msg->count >= STM32F7_I2C_DMA_LEN_MIN) { > > Are you using DMA for every message with a length >= 1? The setup of > that might be more expensive than the DMA gain, if so. > Well yes. I am in charge of DMA IPs as well. I2C is the only devices that I had to test DMA outside standard DMA Engine test. Quite convenient. I believe to stress both I2C and DMA, this value was relevant. Now I agree this value can be tuned a little bit. I might raise this threshold in V3.