Hi, Laurent

On 12/2/2014 6:26 AM, Laurent Pinchart wrote:

Hi Josh,

(CC'ing the devicetree at vger.kernel.org mailing list)

Thank you for the patch.

On Friday 28 November 2014 18:28:26 Josh Wu wrote:

quoted

The master clock can be optional. It's a common clock framework clock.
It can make sensor output a pixel clock to the camera interface.

If you just use a external oscillator clock as the master clock, then,
just don't need set 'mck' in dt node.

Signed-off-by: Josh Wu <redacted>
---
  drivers/media/i2c/soc_camera/ov2640.c | 25 +++++++++++++++++++++++++
  1 file changed, 25 insertions(+)

diff --git a/drivers/media/i2c/soc_camera/ov2640.c

b/drivers/media/i2c/soc_camera/ov2640.c index 6506126..06c2aa9 100644

--- a/drivers/media/i2c/soc_camera/ov2640.c
+++ b/drivers/media/i2c/soc_camera/ov2640.c

@@ -13,6 +13,7 @@
   * published by the Free Software Foundation.
   */

+#include <linux/clk.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/i2c.h>

@@ -31,6 +32,8 @@

  #define VAL_SET(x, mask, rshift, lshift)  \
  		((((x) >> rshift) & mask) << lshift)
+#define DEFAULT_MASTER_CLK_FREQ		25000000
+
  /*
   * DSP registers
   * register offset for BANK_SEL == BANK_SEL_DSP

@@ -284,6 +287,7 @@ struct ov2640_priv {
  	struct v4l2_ctrl_handler	hdl;
  	u32	cfmt_code;
  	struct v4l2_clk			*clk;
+	struct clk			*master_clk;
  	const struct ov2640_win_size	*win;

  	struct soc_camera_subdev_desc	ssdd_dt;

@@ -746,6 +750,7 @@ static int ov2640_s_power(struct v4l2_subdev *sd, int

on) struct soc_camera_subdev_desc *ssdd = soc_camera_i2c_to_desc(client);
struct ov2640_priv *priv = to_ov2640(client);
  	struct v4l2_clk *clk;
+	int ret = 0;

  	if (!priv->clk) {
  		clk = v4l2_clk_get(&client->dev, "mclk");

@@ -755,6 +760,16 @@ static int ov2640_s_power(struct v4l2_subdev *sd, int

on) priv->clk = clk;
  	}

+	if (!IS_ERR(priv->master_clk)) {

The clock should be mandatory, you can thus drop this check.

OK. sure.

quoted

+		if (on)
+			ret = clk_prepare_enable(priv->master_clk);
+		else
+			clk_disable_unprepare(priv->master_clk);
+
+		if (ret)
+			return ret;

You can move the error check inside the first branch of the if and remove the
ret = 0 initialization above.

quoted

+	}
+
  	return soc_camera_set_power(&client->dev, ssdd, priv->clk, on);

If this call fails you should disable or enable the clock to undo the
enable/disable above.

ah, I totally forget this. will fix in next version. Thanks.

quoted

  }

@@ -1153,6 +1168,16 @@ static int ov2640_probe(struct i2c_client *client,
  		}
  	}

+	priv->master_clk = devm_clk_get(&client->dev, "mck");
+	if (!IS_ERR(priv->master_clk)) {
+		/* Set ISI_MCK's frequency, it should be faster than pixel
+		 * clock.
+		 */
+		ret = clk_set_rate(priv->master_clk, DEFAULT_MASTER_CLK_FREQ);

The clock frequency should be system-dependent. For the DT case an easy
implementation would be to use the assigned-clock-rates to set the desired
clock frequency is case of a variable clock, as adding a sensor-specific
property to specify the desired clock frequency only to read that property in
the driver and call clk_set_rate() seems a bit pointless to me.

I tried assigned-clock-rates and it works fine.
The only issue is the it cannot used by multiple nodes. But I think I 
can put a comments in the dt node for this.
Thanks.

Best Regards,
Josh Wu

quoted

+		if (ret < 0)
+			return ret;
+	}
+
  	v4l2_i2c_subdev_init(&priv->subdev, client, &ov2640_subdev_ops);
  	v4l2_ctrl_handler_init(&priv->hdl, 2);
  	v4l2_ctrl_new_std(&priv->hdl, &ov2640_ctrl_ops,