V4L/DVB (5691): Ov7670: reset clkrc in rgb565 mode

A bug in the ov7670 sensor causes it to introduce noise unless the CLKRC
register is rewritten *after* setting the image mode.  Naturally,
resetting CLKRC in this way will cause other modes to fail.  So
carefully poke the register only when indicated.

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

1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/media/video/ov7670.c b/drivers/media/video/ov7670.c
index 03bc369a9e4..3ceb8a6249d 100644
--- a/drivers/media/video/ov7670.c
+++ b/drivers/media/video/ov7670.c
@@ -720,12 +720,22 @@ static int ov7670_s_fmt(struct i2c_client *c, struct v4l2_format *fmt)
         struct ov7670_format_struct *ovfmt;
         struct ov7670_win_size *wsize;
         struct ov7670_info *info = i2c_get_clientdata(c);
-        unsigned char com7;
+        unsigned char com7, clkrc;
 
         ret = ov7670_try_fmt(c, 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(c, 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
          * to set it absolutely here, as long as the format-specific
@@ -744,7 +754,10 @@ static int ov7670_s_fmt(struct i2c_client *c, struct v4l2_format *fmt)
         if (wsize->regs)
                 ret = ov7670_write_array(c, wsize->regs);
         info->fmt = ovfmt;
-        return 0;
+
+        if (fmt->fmt.pix.pixelformat == V4L2_PIX_FMT_RGB565 && ret == 0)
+                ret = ov7670_write(c, REG_CLKRC, clkrc);
+        return ret;
 }
 
 /*
@@ -1267,7 +1280,9 @@ static int ov7670_attach(struct i2c_adapter *adapter)
         ret = ov7670_detect(client);
         if (ret)
                 goto out_free_info;
-        i2c_attach_client(client);
+        ret = i2c_attach_client(client);
+        if (ret)
+                goto out_free_info;
         return 0;
 
   out_free_info: