VC4's DSI1 has a bug where the AXI connection is broken for 32-bit
writes from the CPU, so we use the DMA engine to DMA 32-bit values
into registers instead. That sleeps, so we can't do it from the top
half.
As a solution, use an interrupt thread so that all our writes happen
when sleeping is is allowed.
v2: Use IRQF_ONESHOT (suggested by Boris)
v3: Style nitpicks.
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20171014001255.32005-1-eric@anholt.net
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
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