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m68k: mac: Don't send IOP message until channel is idle

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[ 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: 1da177e4c3 ("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>
This commit is contained in:
Finn Thain 2020-05-31 09:12:13 +10:00 committed by Greg Kroah-Hartman
parent 38702b9081
commit b8ad79dde6
1 changed files with 3 additions and 6 deletions
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9
arch/m68k/mac/iop.c
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@ -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;
}