Rob Herring [off-list ref] writes:

The BCM2835 AUX SPI has a shared interrupt line (with AUX UART).
Downstream fixes this with an AUX irqchip to demux the IRQ sources and a
DT change which breaks compatibility with older kernels. The AUX irqchip
was already rejected for upstream[1] and the DT change would break
working systems if the DTB is updated to a newer one. The latter issue
was brought to my attention by Alex Graf.

The root cause however is a bug in the shared handler. A shared handler
must correctly identify it actually handled an interrupt. The handler
here was processing data whether interrupts were enabled or not.
It would return IRQ_HANDLED if there was any data and not only when
there was an actual interrupt pending. The result is that another
device's IRQ could cause the SPI's IRQ handler to run and process data
when the the SPI driver working in polled mode. Fix this by adding a
check in the IRQ handler that the TXEMPTY or IDLE interrupts are enabled
and always return IRQ_NONE when they are not.

FWIW, I see v1 already applied in -next.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20180530/0171381b/attachment.sig>