Skip to content

Commit

Permalink
[media] media: ov7670: calculate framerate properly for ov7675
Browse files Browse the repository at this point in the history 
According to the datasheet ov7675 uses a formula to achieve
the desired framerate that is different from the operations
done in the current code.
In fact, this formula should apply to ov7670 too. This would
mean that current code is wrong but, in order to preserve
compatibility, the new formula will be used for ov7675 only.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
  • Loading branch information
Javier Martin authored and Mauro Carvalho Chehab committed Feb 8, 2013
1 parent f748cd3 commit f6dd927
Showing 1 changed file with 118 additions and 18 deletions.
136 changes: 118 additions & 18 deletions drivers/media/i2c/ov7670.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,8 @@ MODULE_PARM_DESC(debug, "Debug level (0-1)");
*/
#define OV7670_I2C_ADDR 0x42

#define PLL_FACTOR 4

/* Registers */
#define REG_GAIN 0x00 /* Gain lower 8 bits (rest in vref) */
#define REG_BLUE 0x01 /* blue gain */
Expand Down Expand Up @@ -164,6 +166,12 @@ MODULE_PARM_DESC(debug, "Debug level (0-1)");

#define REG_GFIX 0x69 /* Fix gain control */

#define REG_DBLV 0x6b /* PLL control an debugging */
#define DBLV_BYPASS 0x00 /* Bypass PLL */
#define DBLV_X4 0x01 /* clock x4 */
#define DBLV_X6 0x10 /* clock x6 */
#define DBLV_X8 0x11 /* clock x8 */

#define REG_REG76 0x76 /* OV's name */
#define R76_BLKPCOR 0x80 /* Black pixel correction enable */
#define R76_WHTPCOR 0x40 /* White pixel correction enable */
Expand Down Expand Up @@ -203,6 +211,9 @@ struct ov7670_devtype {
/* formats supported for each model */
struct ov7670_win_size *win_sizes;
unsigned int n_win_sizes;
/* callbacks for frame rate control */
int (*set_framerate)(struct v4l2_subdev *, struct v4l2_fract *);
void (*get_framerate)(struct v4l2_subdev *, struct v4l2_fract *);
};

/*
Expand Down Expand Up @@ -739,6 +750,98 @@ static struct ov7670_win_size ov7675_win_sizes[] = {
}
};

static void ov7675_get_framerate(struct v4l2_subdev *sd,
struct v4l2_fract *tpf)
{
struct ov7670_info *info = to_state(sd);
u32 clkrc = info->clkrc;
u32 pll_factor = PLL_FACTOR;

clkrc++;
if (info->fmt->mbus_code == V4L2_MBUS_FMT_SBGGR8_1X8)
clkrc = (clkrc >> 1);

tpf->numerator = 1;
tpf->denominator = (5 * pll_factor * info->clock_speed) /
(4 * clkrc);
}

static int ov7675_set_framerate(struct v4l2_subdev *sd,
struct v4l2_fract *tpf)
{
struct ov7670_info *info = to_state(sd);
u32 clkrc;
u32 pll_factor = PLL_FACTOR;
int ret;

/*
* The formula is fps = 5/4*pixclk for YUV/RGB and
* fps = 5/2*pixclk for RAW.
*
* pixclk = clock_speed / (clkrc + 1) * PLLfactor
*
*/
if (tpf->numerator == 0 || tpf->denominator == 0) {
clkrc = 0;
} else {
clkrc = (5 * pll_factor * info->clock_speed * tpf->numerator) /
(4 * tpf->denominator);
if (info->fmt->mbus_code == V4L2_MBUS_FMT_SBGGR8_1X8)
clkrc = (clkrc << 1);
clkrc--;
}

/*
* The datasheet claims that clkrc = 0 will divide the input clock by 1
* but we've checked with an oscilloscope that it divides by 2 instead.
* So, if clkrc = 0 just bypass the divider.
*/
if (clkrc <= 0)
clkrc = CLK_EXT;
else if (clkrc > CLK_SCALE)
clkrc = CLK_SCALE;
info->clkrc = clkrc;

/* Recalculate frame rate */
ov7675_get_framerate(sd, tpf);

ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
if (ret < 0)
return ret;
return ov7670_write(sd, REG_DBLV, DBLV_X4);
}

static void ov7670_get_framerate_legacy(struct v4l2_subdev *sd,
struct v4l2_fract *tpf)
{
struct ov7670_info *info = to_state(sd);

tpf->numerator = 1;
tpf->denominator = info->clock_speed;
if ((info->clkrc & CLK_EXT) == 0 && (info->clkrc & CLK_SCALE) > 1)
tpf->denominator /= (info->clkrc & CLK_SCALE);
}

static int ov7670_set_framerate_legacy(struct v4l2_subdev *sd,
struct v4l2_fract *tpf)
{
struct ov7670_info *info = to_state(sd);
int div;

if (tpf->numerator == 0 || tpf->denominator == 0)
div = 1; /* Reset to full rate */
else
div = (tpf->numerator * info->clock_speed) / tpf->denominator;
if (div == 0)
div = 1;
else if (div > CLK_SCALE)
div = CLK_SCALE;
info->clkrc = (info->clkrc & 0x80) | div;
tpf->numerator = 1;
tpf->denominator = info->clock_speed / div;
return ov7670_write(sd, REG_CLKRC, info->clkrc);
}

/*
* Store a set of start/stop values into the camera.
*/
Expand Down Expand Up @@ -913,10 +1016,8 @@ static int ov7670_g_parm(struct v4l2_subdev *sd, struct v4l2_streamparm *parms)

memset(cp, 0, sizeof(struct v4l2_captureparm));
cp->capability = V4L2_CAP_TIMEPERFRAME;
cp->timeperframe.numerator = 1;
cp->timeperframe.denominator = info->clock_speed;
if ((info->clkrc & CLK_EXT) == 0 && (info->clkrc & CLK_SCALE) > 1)
cp->timeperframe.denominator /= (info->clkrc & CLK_SCALE);
info->devtype->get_framerate(sd, &cp->timeperframe);

return 0;
}

Expand All @@ -925,25 +1026,13 @@ static int ov7670_s_parm(struct v4l2_subdev *sd, struct v4l2_streamparm *parms)
struct v4l2_captureparm *cp = &parms->parm.capture;
struct v4l2_fract *tpf = &cp->timeperframe;
struct ov7670_info *info = to_state(sd);
int div;

if (parms->type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
return -EINVAL;
if (cp->extendedmode != 0)
return -EINVAL;

if (tpf->numerator == 0 || tpf->denominator == 0)
div = 1; /* Reset to full rate */
else
div = (tpf->numerator * info->clock_speed) / tpf->denominator;
if (div == 0)
div = 1;
else if (div > CLK_SCALE)
div = CLK_SCALE;
info->clkrc = (info->clkrc & 0x80) | div;
tpf->numerator = 1;
tpf->denominator = info->clock_speed / div;
return ov7670_write(sd, REG_CLKRC, info->clkrc);
return info->devtype->set_framerate(sd, tpf);
}


Expand Down Expand Up @@ -1560,16 +1649,21 @@ static const struct ov7670_devtype ov7670_devdata[] = {
[MODEL_OV7670] = {
.win_sizes = ov7670_win_sizes,
.n_win_sizes = ARRAY_SIZE(ov7670_win_sizes),
.set_framerate = ov7670_set_framerate_legacy,
.get_framerate = ov7670_get_framerate_legacy,
},
[MODEL_OV7675] = {
.win_sizes = ov7675_win_sizes,
.n_win_sizes = ARRAY_SIZE(ov7675_win_sizes),
.set_framerate = ov7675_set_framerate,
.get_framerate = ov7675_get_framerate,
},
};

static int ov7670_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct v4l2_fract tpf;
struct v4l2_subdev *sd;
struct ov7670_info *info;
int ret;
Expand Down Expand Up @@ -1611,7 +1705,13 @@ static int ov7670_probe(struct i2c_client *client,
info->devtype = &ov7670_devdata[id->driver_data];
info->fmt = &ov7670_formats[0];
info->sat = 128; /* Review this */
info->clkrc = info->clock_speed / 30;
info->clkrc = 0;

/* Set default frame rate to 30 fps */
tpf.numerator = 1;
tpf.denominator = 30;
info->devtype->set_framerate(sd, &tpf);

return 0;
}

Expand Down

0 comments on commit f6dd927

Please sign in to comment.