[PATCH v2 4/5] media: ov7670: add possibility to bypass pll for ov7675.

[Javier Martin]

For a frame rate of 30 fps a pixclk of 24MHz is needed. For those
cases where the ov7670 has a clean 24MHz input (xvclk) the PLL
can be bypassed.

This will result in a value of clkrc of 1, which means that in practice
pixclk = xvclk (input clock)

Acked-by: Jonathan Corbet <cor...@lwn.net>
Signed-off-by: Javier Martin <javier.mar...@vista-silicon.com>
---
Changes since v1:
 - Added changelog.

---
 drivers/media/i2c/ov7670.c |   28 ++++++++++++++++++++++++++--
 include/media/ov7670.h     |    1 +
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
index cb62d08..559c23e 100644
--- a/drivers/media/i2c/ov7670.c
+++ b/drivers/media/i2c/ov7670.c
@@ -230,6 +230,7 @@ struct ov7670_info {
        int clock_speed;                /* External clock speed (MHz) */
        u8 clkrc;                       /* Clock divider value */
        bool use_smbus;                 /* Use smbus I/O instead of I2C */
+       bool pll_bypass;
        const struct ov7670_devtype *devtype; /* Device specifics */
 };
 
@@ -755,7 +756,12 @@ static void ov7675_get_framerate(struct v4l2_subdev *sd,
 {
        struct ov7670_info *info = to_state(sd);
        u32 clkrc = info->clkrc;
-       u32 pll_factor = PLL_FACTOR;
+       int pll_factor;
+
+       if (info->pll_bypass)
+               pll_factor = 1;
+       else
+               pll_factor = PLL_FACTOR;
 
        clkrc++;
        if (info->fmt->mbus_code == V4L2_MBUS_FMT_SBGGR8_1X8)
@@ -771,7 +777,7 @@ static int ov7675_set_framerate(struct v4l2_subdev *sd,
 {
        struct ov7670_info *info = to_state(sd);
        u32 clkrc;
-       u32 pll_factor = PLL_FACTOR;
+       int pll_factor;
        int ret;
 
        /*
@@ -781,6 +787,16 @@ static int ov7675_set_framerate(struct v4l2_subdev *sd,
         * pixclk = clock_speed / (clkrc + 1) * PLLfactor
         *
         */
+       if (info->pll_bypass) {
+               pll_factor = 1;
+               ret = ov7670_write(sd, REG_DBLV, DBLV_BYPASS);
+       } else {
+               pll_factor = PLL_FACTOR;
+               ret = ov7670_write(sd, REG_DBLV, DBLV_X4);
+       }
+       if (ret < 0)
+               return ret;
+
        if (tpf->numerator == 0 || tpf->denominator == 0) {
                clkrc = 0;
        } else {
@@ -808,6 +824,7 @@ static int ov7675_set_framerate(struct v4l2_subdev *sd,
        ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
        if (ret < 0)
                return ret;
+
        return ov7670_write(sd, REG_DBLV, DBLV_X4);
 }
 
@@ -1688,6 +1705,13 @@ static int ov7670_probe(struct i2c_client *client,
 
                if (config->clock_speed)
                        info->clock_speed = config->clock_speed;
+
+               /*
+                * It should be allowed for ov7670 too when it is migrated to
+                * the new frame rate formula.
+                */
+               if (config->pll_bypass && id->driver_data != MODEL_OV7670)
+                       info->pll_bypass = true;
        }
 
        /* Make sure it's an ov7670 */
diff --git a/include/media/ov7670.h b/include/media/ov7670.h
index b133bc1..a68c8bb 100644
--- a/include/media/ov7670.h
+++ b/include/media/ov7670.h
@@ -15,6 +15,7 @@ struct ov7670_config {
        int min_height;                 /* Filter out smaller sizes */
        int clock_speed;                /* External clock speed (MHz) */
        bool use_smbus;                 /* Use smbus I/O instead of I2C */
+       bool pll_bypass;                /* Choose whether to bypass the PLL */
 };
 
 #endif
-- 
1.7.9.5

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