On Tue, Feb 18, 2020 at 08:03:10AM +0100, Uwe Kleine-König wrote: > On Tue, Feb 18, 2020 at 05:50:08AM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > 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. > > To complete these fixes you also want to backport > > 101aa46bd221 serial: imx: fix a race condition in receive path If so, it needs to also go to 4.19.y, and someone needs to provide a working backport for both places :) thanks, greg k-h
