[media] cx23885[v4]: Fix interrupt storm when enabling IR receiver

Apparently the Flatiron genereates an interrupt after the built-in self
test for each of its left and right channels has completed.

Apparently Conexant wire-OR'ed the Flatiron's interrupt output with the
interrupt output of the CX23885 A/V core.

Those interrupts need to be handled, otherwise, they generate an
interrrupt request storm.

So:

- Add flatiron readreg and writereg functions prototypes
  on a new header file;
- Modify the av interrupt handler to cleanup flatiron IRQs if no other
  interrupt handling happens.

Signed-off-by: Luis Alves <ljalvs@gmail.com>
Acked-by: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/pci/cx23885/cx23885-av.c

@@ -23,6 +23,7 @@
 
 #include "cx23885.h"
 #include "cx23885-av.h"
+#include "cx23885-video.h"
 
 void cx23885_av_work_handler(struct work_struct *work)
 {
@@ -32,5 +33,17 @@ void cx23885_av_work_handler(struct work_struct *work)
 
 	v4l2_subdev_call(dev->sd_cx25840, core, interrupt_service_routine,
 			 PCI_MSK_AV_CORE, &handled);
+
+	/* Getting here with the interrupt not handled
+	   then probbaly flatiron does have pending interrupts.
+	*/
+	if (!handled) {
+		/* clear left and right adc channel interrupt request flag */
+		cx23885_flatiron_write(dev, 0x1f,
+			cx23885_flatiron_read(dev, 0x1f) | 0x80);
+		cx23885_flatiron_write(dev, 0x23,
+			cx23885_flatiron_read(dev, 0x23) | 0x80);
+	}
+
 	cx23885_irq_enable(dev, PCI_MSK_AV_CORE);
 }

drivers/media/pci/cx23885/cx23885-video.c

@@ -417,7 +417,7 @@ static void res_free(struct cx23885_dev *dev, struct cx23885_fh *fh,
 	mutex_unlock(&dev->lock);
 }
 
-static int cx23885_flatiron_write(struct cx23885_dev *dev, u8 reg, u8 data)
+int cx23885_flatiron_write(struct cx23885_dev *dev, u8 reg, u8 data)
 {
 	/* 8 bit registers, 8 bit values */
 	u8 buf[] = { reg, data };
@@ -428,7 +428,7 @@ static int cx23885_flatiron_write(struct cx23885_dev *dev, u8 reg, u8 data)
 	return i2c_transfer(&dev->i2c_bus[2].i2c_adap, &msg, 1);
 }
 
-static u8 cx23885_flatiron_read(struct cx23885_dev *dev, u8 reg)
+u8 cx23885_flatiron_read(struct cx23885_dev *dev, u8 reg)
 {
 	/* 8 bit registers, 8 bit values */
 	int ret;

drivers/media/pci/cx23885/cx23885-video.h

@@ -0,0 +1,26 @@
+/*
+ *  Driver for the Conexant CX23885/7/8 PCIe bridge
+ *
+ *  Copyright (C) 2010  Andy Walls <awalls@md.metrocast.net>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version 2
+ *  of the License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ *  02110-1301, USA.
+ */
+
+#ifndef _CX23885_VIDEO_H_
+#define _CX23885_VIDEO_H_
+int cx23885_flatiron_write(struct cx23885_dev *dev, u8 reg, u8 data);
+u8 cx23885_flatiron_read(struct cx23885_dev *dev, u8 reg);
+#endif