On 3/11/21 12:18 AM, Wolfram Sang wrote: > >> Bummer. What is really weird is that you see clock stretching under >> CPU load. Normally clock stretching is triggered by the device, not >> by the host. > > One example: Some hosts need an interrupt per byte to know if they > should send ACK or NACK. If that interrupt is delayed, they stretch the > clock. > Indeed, the i2c-mpc driver sends TXAK (only) after receiving that interrupt. Since that is running in the context of the user process, that may well be delayed substantially on a loaded system. Maybe the interrupt handler will need to play a more active role in the i2c-mpc driver. Alternatively, the transfer function could be handled by a high priority kernel thread. Guenter
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