Hi!
[ Upstream commit b867eef4cf548cd9541225aadcdcee644669b9e1 ]
The SPIE register contains counts for the TX FIFO so any time the irq handler was invoked we would attempt to process the RX/TX fifos. Use the SPIM value to mask the events so that we only process interrupts that were expected.
This was a latent issue exposed by commit 3282a3da25bd ("powerpc/64: Implement soft interrupt replay in C").
We don't seem to have commit 3282... in 4.19, so we don't need this one in 4.19-stable according to the changelog.
Technically 3282... exposed the issue by making it more likely to happen so 4.19 might just have a really low probability of seeing the issue (I think I did try reproducing it on kernels of that vintage). Personally I'm not too fussed the kernel versions I care about have the fix. Maybe someone from NXP cares enough to pursue it.
Okay, I guess low-probability bugs are still fair game for -stable. The commit was not dropped from 4.19, so nothing needs to be done here.
Sorry for the noise, Pavel