Hi Josh,
(CC'ing the devicet...@vger.kernel.org mailing list)
Thank you for the patch.
On Friday 28 November 2014 18:28:26 Josh Wu wrote:
> 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 <josh...@atmel.com>
> ---
> 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.
> + 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.
> + }
> +
> 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.
> }
>
> @@ -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.
> + 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,
--
Regards,
Laurent Pinchart
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