[PATCH AUTOSEL 4.14 08/14] m68k: mac: Don't send IOP message until channel is idle

Sasha Levin
2020-08-08T23:42:01Z

From: Finn Thain <fthain@telegraphics.com.au>

[ Upstream commit aeb445bf2194d83e12e85bf5c65baaf1f093bd8f ]

In the following sequence of calls, iop_do_send() gets called when the
"send" channel is not in the IOP_MSG_IDLE state:

iop_ism_irq()
iop_handle_send()
(msg->handler)()
iop_send_message()
iop_do_send()

Avoid this by testing the channel state before calling iop_do_send().

When sending, and iop_send_queue is empty, call iop_do_send() because
the channel is idle. If iop_send_queue is not empty, iop_do_send() will
get called later by iop_handle_send().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Cc: Joshua Thompson <funaho@jurai.org>
Link: https://lore.kernel.org/r/6d667c39e53865661fa5a48f16829d18ed8abe54.1590880333.git.fthain@telegraphics.com.au
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/m68k/mac/iop.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/m68k/mac/iop.c b/arch/m68k/mac/iop.c
index 4c1e606e7d03b..fb61af5ac4ab8 100644
--- a/arch/m68k/mac/iop.c
+++ b/arch/m68k/mac/iop.c
@@ -416,7 +416,8 @@ static void iop_handle_send(uint iop_num, uint chan)
msg->status = IOP_MSGSTATUS_UNUSED;
msg = msg->next;
iop_send_queue[iop_num][chan] = msg;
- if (msg) iop_do_send(msg);
+ if (msg && iop_readb(iop, IOP_ADDR_SEND_STATE + chan) == IOP_MSG_IDLE)
+ iop_do_send(msg);
}

/*
@@ -490,16 +491,12 @@ int iop_send_message(uint iop_num, uint chan, void *privdata,

if (!(q = iop_send_queue[iop_num][chan])) {
iop_send_queue[iop_num][chan] = msg;
+ iop_do_send(msg);
} else {
while (q->next) q = q->next;
q->next = msg;
}

- if (iop_readb(iop_base[iop_num],
- IOP_ADDR_SEND_STATE + chan) == IOP_MSG_IDLE) {
- iop_do_send(msg);
- }
-
return 0;
}

--
2.25.1