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Subject[ review 25/28] serial: clear proper MPSC interrupt cause bits
The interrupt clearing code in mpsc_sdma_intr_ack() mistakenly clears the
interrupt for both controllers instead of just the one its supposed to.
This can result in the other controller appearing to hang because its
interrupt was effectively lost.

So, don't clear the interrupt cause bits for both MPSC controllers when
clearing the interrupt for one of them. Just clear the one that is
supposed to be cleared.

Signed-off-by: Jay Lubomirski <>
Acked-by: Mark A. Greer <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Chris Wright <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/serial/mpsc.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c
index 3d2fcc5..64ed5ef 100644
--- a/drivers/serial/mpsc.c
+++ b/drivers/serial/mpsc.c
@@ -502,7 +502,8 @@ mpsc_sdma_intr_ack(struct mpsc_port_info *pi)

if (pi->mirror_regs)
pi->shared_regs->SDMA_INTR_CAUSE_m = 0;
- writel(0, pi->shared_regs->sdma_intr_base + SDMA_INTR_CAUSE);
+ writeb(0x00, pi->shared_regs->sdma_intr_base + SDMA_INTR_CAUSE +
+ pi->port.line);

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