[PATCH] cx23885[v2]: Fix IR interrupt storm.

[Luis Alves <ljalvs@gmail.com>]

Hi all,
This path is meant to be up-streamed.

Andy has a nice explanation for the interrupt storm when
enabling the IR interrupt:

The flatiron core (the audio adc) signals the end of its self-test
with an interrupt. Since the flatiron irq seems OR-wired
with the IR irq the result is this interrupt storm.
This i2c tranfers will clear the flatiron interrupts - the left
and right channels self-tests.

Also as suggested by Andy I moved the i2c transfers to the
cx23885 av core interrupt handling worker. If any spurious
interrupt happens we silence them.

The flatiron has some dedicated register read/write functions but are
not exported so Antti just suggested to call the i2c_transfer directly.

Tested in the TBS6981 Dual DVB-S2 card.

PS: I've found this i2c_transfers in TBS media tree, more precisely
in the cx23885-i2c.c file.

Regards,
Luis


Signed-off-by: Luis Alves <ljalvs@gmail.com>
---
 drivers/media/pci/cx23885/cx23885-av.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/media/pci/cx23885/cx23885-av.c b/drivers/media/pci/cx23885/cx23885-av.c
index e958a01..d33570f 100644
--- a/drivers/media/pci/cx23885/cx23885-av.c
+++ b/drivers/media/pci/cx23885/cx23885-av.c
@@ -29,8 +29,25 @@ void cx23885_av_work_handler(struct work_struct *work)
 	struct cx23885_dev *dev =
 			   container_of(work, struct cx23885_dev, cx25840_work);
 	bool handled;
+	char buffer[2];
+	struct i2c_msg msg = {
+		.addr = 0x98 >> 1,
+		.flags = 0,
+		.len = 2,
+		.buf = buffer,
+	};
 
 	v4l2_subdev_call(dev->sd_cx25840, core, interrupt_service_routine,
 			 PCI_MSK_AV_CORE, &handled);
+
+	if (!handled) {
+		/* clear any pending flatiron interrupts */
+		buffer[0] = 0x1f;
+		buffer[1] = 0x80;
+		i2c_transfer(&dev->i2c_bus[2].i2c_adap, &msg, 1);
+		buffer[0] = 0x23;
+		i2c_transfer(&dev->i2c_bus[2].i2c_adap, &msg, 1);
+	}
+
 	cx23885_irq_enable(dev, PCI_MSK_AV_CORE);
 }
-- 
1.7.9.5