[ Upstream commit 9468ab84032f96496e998cfa173cd1d0ac316bcd ]
Unisoc mailbox has no way to be enabled/disabled for any single channel.
They can only be set to startup or shutdown as a whole device at same time.
Add a variable to count references to avoid mailbox FIFO being reset
unexpectedly when clients are requesting or freeing channels.
Also add a lock to dismiss possible conflicts from register r/w in
different startup or shutdown threads. And fix the crash problem when early
interrupts come from channel which has not been requested by client yet.
Fixes: ca27fc26cd ("mailbox: sprd: Add Spreadtrum mailbox driver")
Signed-off-by: Orson Zhai <orson.zhai@unisoc.com>
Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
cadbba5ec8