On 06/25/2018 09:38 PM, Wolfram Sang wrote:

On Wed, Jun 13, 2018 at 02:36:16PM -0500, Eddie James wrote:

quoted

Add abort procedure for failed transfers. Add engine and bus reset
procedures to recover from as many faults as possible.

I think this is a way too aggressive recovery. Your are doing the 9
pulse toggles basically on any error while this is only when the device
keeps SDA low and you want to recover from that. If SDA is not stuck
low, sending a STOP should do. Or do you have a known case where this is
not going to work?

It is aggressive, but I don't see the harm in doing this on every error. 
There are some other error conditions with this hardware which may 
require the clock toggling, such as "bus arbitration lost." I think this 
is the safest option for this hardware, and this routine has been tested 
for many years.

Also, you implement the pulse toggling manually. Can't you just populate
{get|set}_{scl|sda} and use the generic routine we have in the core?

I see that the generic implementation breaks the loop if it sees the 
clock isn't high after setting it, or if SDA goes high. I think it's 
safer to finish the reset for our hardware. Plus, we actually have 
different registers for setting 0 or 1 to the clock/data, so we save 
some cpu cycles by doing it directly instead of implementing set_scl/sda 
and having to check val every time :)

If you feel very strongly that this recovery procedure needs to be 
reduced, then I will work on that and have to do some extensive testing.

Thanks!
Eddie