[PATCH linux dev-4.7 v2] drivers/fsi: Add delay before sampling input on SDA

Jeremy Kerr jk at ozlabs.org
Mon Mar 20 16:33:47 AEDT 2017

Hi Chris,

> During high cpu loads the SDA in line can shift relative to the
> clock signal which can corrupt the received input data.  Slow
> down the time to sample input to account for this.

This looks much better than the previous patch, but do you know why high
CPU loads affect this? All of the GPIO interactions are performed with
the single spinlock held, so CPU load should have no bearing on the
timing of the bit-banging - the driver has exclusive use of the CPU
during a FSI transaction.

Can you elaborate on the symptoms of this?

One thing that looks a little suspicious to me is that you're running
the clock during the echo delay time, so you're potentially feeding
random data to the slave...



More information about the openbmc mailing list