V4L/DVB: ov7670: Avoid reading clkrc

Reading the clkrc register creates flaky behavior in some situations, and
we can easily track its state separately.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/video/ov7670.c b/drivers/media/video/ov7670.c
index b44762adb1e9e30fd07ccbee3085c681df2d77f3..b2e6f8e730a32cb664fbca7c6adec51459eb8926 100644 (file)
--- a/drivers/media/video/ov7670.c
+++ b/drivers/media/video/ov7670.c
@@ -198,6 +198,7 @@ struct ov7670_info {
        struct ov7670_format_struct *fmt;  /* Current format */
        unsigned char sat;              /* Saturation value */
        int hue;                        /* Hue value */
+       u8 clkrc;                       /* Clock divider value */
 };
 
 static inline struct ov7670_info *to_state(struct v4l2_subdev *sd)
@@ -744,21 +745,11 @@ static int ov7670_s_fmt(struct v4l2_subdev *sd, struct v4l2_format *fmt)
        struct ov7670_format_struct *ovfmt;
        struct ov7670_win_size *wsize;
        struct ov7670_info *info = to_state(sd);
-       unsigned char com7, clkrc = 0;
+       unsigned char com7;
 
        ret = ov7670_try_fmt_internal(sd, fmt, &ovfmt, &wsize);
        if (ret)
                return ret;
-       /*
-        * HACK: if we're running rgb565 we need to grab then rewrite
-        * CLKRC.  If we're *not*, however, then rewriting clkrc hoses
-        * the colors.
-        */
-       if (fmt->fmt.pix.pixelformat == V4L2_PIX_FMT_RGB565) {
-               ret = ov7670_read(sd, REG_CLKRC, &clkrc);
-               if (ret)
-                       return ret;
-       }
        /*
         * COM7 is a pain in the ass, it doesn't like to be read then
         * quickly written afterward.  But we have everything we need
@@ -779,8 +770,14 @@ static int ov7670_s_fmt(struct v4l2_subdev *sd, struct v4l2_format *fmt)
                ret = ov7670_write_array(sd, wsize->regs);
        info->fmt = ovfmt;
 
+       /*
+        * If we're running RGB565, we must rewrite clkrc after setting
+        * the other parameters or the image looks poor.  If we're *not*
+        * doing RGB565, we must not rewrite clkrc or the image looks
+        * *really* poor.
+        */
        if (fmt->fmt.pix.pixelformat == V4L2_PIX_FMT_RGB565 && ret == 0)
-               ret = ov7670_write(sd, REG_CLKRC, clkrc);
+               ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
        return ret;
 }
 
@@ -791,20 +788,17 @@ static int ov7670_s_fmt(struct v4l2_subdev *sd, struct v4l2_format *fmt)
 static int ov7670_g_parm(struct v4l2_subdev *sd, struct v4l2_streamparm *parms)
 {
        struct v4l2_captureparm *cp = &parms->parm.capture;
-       unsigned char clkrc;
-       int ret;
+       struct ov7670_info *info = to_state(sd);
 
        if (parms->type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
                return -EINVAL;
-       ret = ov7670_read(sd, REG_CLKRC, &clkrc);
-       if (ret < 0)
-               return ret;
+
        memset(cp, 0, sizeof(struct v4l2_captureparm));
        cp->capability = V4L2_CAP_TIMEPERFRAME;
        cp->timeperframe.numerator = 1;
        cp->timeperframe.denominator = OV7670_FRAME_RATE;
-       if ((clkrc & CLK_EXT) == 0 && (clkrc & CLK_SCALE) > 1)
-               cp->timeperframe.denominator /= (clkrc & CLK_SCALE);
+       if ((info->clkrc & CLK_EXT) == 0 && (info->clkrc & CLK_SCALE) > 1)
+               cp->timeperframe.denominator /= (info->clkrc & CLK_SCALE);
        return 0;
 }
 
@@ -812,6 +806,7 @@ 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);
        unsigned char clkrc;
        int ret, div;
 
@@ -819,12 +814,7 @@ static int ov7670_s_parm(struct v4l2_subdev *sd, struct v4l2_streamparm *parms)
                return -EINVAL;
        if (cp->extendedmode != 0)
                return -EINVAL;
-       /*
-        * CLKRC has a reserved bit, so let's preserve it.
-        */
-       ret = ov7670_read(sd, REG_CLKRC, &clkrc);
-       if (ret < 0)
-               return ret;
+
        if (tpf->numerator == 0 || tpf->denominator == 0)
                div = 1;  /* Reset to full rate */
        else
@@ -833,10 +823,10 @@ static int ov7670_s_parm(struct v4l2_subdev *sd, struct v4l2_streamparm *parms)
                div = 1;
        else if (div > CLK_SCALE)
                div = CLK_SCALE;
-       clkrc = (clkrc & 0x80) | div;
+       info->clkrc = (info->clkrc & 0x80) | div;
        tpf->numerator = 1;
        tpf->denominator = OV7670_FRAME_RATE/div;
-       return ov7670_write(sd, REG_CLKRC, clkrc);
+       return ov7670_write(sd, REG_CLKRC, info->clkrc);
 }
 
 
@@ -1268,6 +1258,7 @@ static int ov7670_probe(struct i2c_client *client,
 
        info->fmt = &ov7670_formats[0];
        info->sat = 128;        /* Review this */
+       info->clkrc = 1;        /* 30fps */
 
        return 0;
 }