V4L/DVB (9598): cx18: Prevent CX23418 from clearing it's outgoing ack interrupts to driver

When the CX23418 CPU unit sent out an ack interrupt to the linux driver, it
also received that interrupt and cleared the flag before the linux driver could
see what the interrupt was for.  This fix prevents the CPU from receiving an
IRQ for it's own outgoing ack's to the linux driver.  This fix is critical now
that the linux driver doesn't poll but relies on these ack interrupts.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/media/video/cx18/cx18-firmware.c b/drivers/media/video/cx18/cx18-firmware.c
index ab02da727519..06f5563d6d5a 100644
--- a/drivers/media/video/cx18/cx18-firmware.c
+++ b/drivers/media/video/cx18/cx18-firmware.c
@@ -380,6 +380,17 @@ int cx18_firmware_init(struct cx18 *cx)
                 if (sz <= 0)
                         return -EIO;
         }
+
+        /*
+         * The CPU firmware apparently sets up to receive an interrupt for it's
+         * outgoing IRQ_CPU_TO_EPU_ACK to us (*boggle*).  We get an interrupt
+         * when it sends us an ack, but by the time we process it, that flag in
+         * the SW2 status register has been cleared by the CPU firmware.
+         * We'll prevent that not so useful behavior by clearing the CPU's
+         * interrupt enables for Ack IRQ's we want to process.
+         */
+        cx18_sw2_irq_disable_cpu(cx, IRQ_CPU_TO_EPU_ACK | IRQ_APU_TO_EPU_ACK);
+
         /* initialize GPIO */
         cx18_write_reg_expect(cx, 0x14001400, 0xc78110, 0x00001400, 0x14001400);
         return 0;