V4L/DVB (12240): mt9v011: add a function to calculate frames per second rate

It is possible to adjust the fps rate by changing some register values.
This is function of the connected Xtal at the camera sensor, being a 27
MHz cristal needed, in order to support 640x480 at 30 fps.

For now, it will only calculate the values for fps. Later patches may
introduce V4L2 ioctls, to allow frequency rate adjustments.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/mt9v011.c

@@ -8,6 +8,7 @@
 #include <linux/i2c.h>
 #include <linux/videodev2.h>
 #include <linux/delay.h>
+#include <asm/div64.h>
 #include <media/v4l2-device.h>
 #include "mt9v011.h"
 #include <media/v4l2-i2c-drv.h>
@@ -57,6 +58,7 @@ static struct v4l2_queryctrl mt9v011_qctrl[] = {
 struct mt9v011 {
 	struct v4l2_subdev sd;
 	unsigned width, height;
+	unsigned xtal;
 
 	u16 global_gain, red_bal, blue_bal;
 };
@@ -131,7 +133,7 @@ static const struct i2c_reg_value mt9v011_init_default[] = {
 		{ R1E_MT9V011_DIGITAL_ZOOM,  0x0000 },
 		{ R20_MT9V011_READ_MODE, 0x1000 },
 
-		{ R07_MT9V011_OUT_CTRL, 0x000a },	/* chip enable */
+		{ R07_MT9V011_OUT_CTRL, 0x0002 },	/* chip enable */
 };
 
 static void set_balance(struct v4l2_subdev *sd)
@@ -154,6 +156,31 @@ static void set_balance(struct v4l2_subdev *sd)
 	mt9v011_write(sd, R2D_MT9V011_RED_GAIN, red_gain);
 }
 
+static void calc_fps(struct v4l2_subdev *sd)
+{
+	struct mt9v011 *core = to_mt9v011(sd);
+	unsigned height, width, hblank, vblank, speed;
+	unsigned row_time, t_time;
+	u64 frames_per_ms;
+	unsigned tmp;
+
+	height = mt9v011_read(sd, R03_MT9V011_HEIGHT);
+	width = mt9v011_read(sd, R04_MT9V011_WIDTH);
+	hblank = mt9v011_read(sd, R05_MT9V011_HBLANK);
+	vblank = mt9v011_read(sd, R06_MT9V011_VBLANK);
+	speed = mt9v011_read(sd, R0A_MT9V011_CLK_SPEED);
+
+	row_time = (width + 113 + hblank) * (speed + 2);
+	t_time = row_time * (height + vblank + 1);
+
+	frames_per_ms = core->xtal * 1000l;
+	do_div(frames_per_ms, t_time);
+	tmp = frames_per_ms;
+
+	v4l2_dbg(1, debug, sd, "Programmed to %u.%03u fps (%d pixel clcks)\n",
+		tmp / 1000, tmp % 1000, t_time);
+}
+
 static void set_res(struct v4l2_subdev *sd)
 {
 	struct mt9v011 *core = to_mt9v011(sd);
@@ -179,6 +206,8 @@ static void set_res(struct v4l2_subdev *sd)
 	mt9v011_write(sd, R01_MT9V011_ROWSTART, vstart);
 	mt9v011_write(sd, R03_MT9V011_HEIGHT, core->height);
 	mt9v011_write(sd, R06_MT9V011_VBLANK, 508 - core->height);
+
+	calc_fps(sd);
 };
 
 static int mt9v011_reset(struct v4l2_subdev *sd, u32 val)
@@ -413,6 +442,7 @@ static int mt9v011_probe(struct i2c_client *c,
 	core->global_gain = 0x0024;
 	core->width  = 640;
 	core->height = 480;
+	core->xtal = 27000000;	/* Hz */
 
 	v4l_info(c, "chip found @ 0x%02x (%s)\n",
 		 c->addr << 1, c->adapter->name);