On Mon, Feb 17, 2020 at 02:08:00PM +0000, Schrempf Frieder wrote: > From: Frieder Schrempf <frieder.schrempf@xxxxxxxxxx> > > A customer of ours has problems with RS485 on i.MX6UL with the latest v4.14 > kernel. They get an exception like below from time to time (the trace is > from an older kernel, but the problem also exists in v4.14.170). > > As the cpuidle state 2 causes large delays for the interrupt that controls the > RS485 RTS signal (which can lead to collisions on the bus), cpuidle state 2 was > disabled on this system. This aspect might cause the exception happening more > often on this system than on other systems with default cpuidle settings. > > Looking for solutions I found Uwe's patches that were applied in v4.17 being > mentioned here [1] and here [2]. In [1] Uwe notes that backporting these fixes > to v4.14 might not be trivial, but I tried and in my opinion found it not to be > too problematic either. > > With the backported patches applied, our customer reports that the exceptions > stopped occuring. Given this and the fact that the problem seems to be known > and quite common, it would be nice to get this into the v4.14 stable tree. Thanks for the backports, both now queued up. greg k-h
