Re: [PATCHv3 04/15] ov7670: get xclk

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On 10/03/17 10:11, Sakari Ailus wrote:
> Hi Hans,
> 
> On Fri, Mar 10, 2017 at 09:55:53AM +0100, Hans Verkuil wrote:
>> On 09/03/17 21:38, Sakari Ailus wrote:
>>> Hi Hans,
>>>
>>> On Mon, Mar 06, 2017 at 03:56:05PM +0100, Hans Verkuil wrote:
>>>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>>>
>>>> Get the clock for this sensor.
>>>>
>>>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>>> ---
>>>>  drivers/media/i2c/ov7670.c | 12 ++++++++++++
>>>>  1 file changed, 12 insertions(+)
>>>>
>>>> diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
>>>> index 50e4466a2b37..da0843617a49 100644
>>>> --- a/drivers/media/i2c/ov7670.c
>>>> +++ b/drivers/media/i2c/ov7670.c
>>>> @@ -10,6 +10,7 @@
>>>>   * This file may be distributed under the terms of the GNU General
>>>>   * Public License, version 2.
>>>>   */
>>>> +#include <linux/clk.h>
>>>>  #include <linux/init.h>
>>>>  #include <linux/module.h>
>>>>  #include <linux/slab.h>
>>>> @@ -227,6 +228,7 @@ struct ov7670_info {
>>>>  		struct v4l2_ctrl *hue;
>>>>  	};
>>>>  	struct ov7670_format_struct *fmt;  /* Current format */
>>>> +	struct clk *clk;
>>>>  	int min_width;			/* Filter out smaller sizes */
>>>>  	int min_height;			/* Filter out smaller sizes */
>>>>  	int clock_speed;		/* External clock speed (MHz) */
>>>> @@ -1587,6 +1589,15 @@ static int ov7670_probe(struct i2c_client *client,
>>>>  			info->pclk_hb_disable = true;
>>>>  	}
>>>>  
>>>> +	info->clk = devm_clk_get(&client->dev, "xclk");
>>>> +	if (IS_ERR(info->clk))
>>>> +		return -EPROBE_DEFER;
>>>> +	clk_prepare_enable(info->clk);
>>>> +
>>>> +	info->clock_speed = clk_get_rate(info->clk) / 1000000;
>>>> +	if (info->clock_speed < 10 || info->clock_speed > 48)
>>>> +		return -EINVAL;
>>>
>>> clk_disable_unprepare() before return?
>>
>> It is my understanding that devm_clk_get will call that for you.
>>
>> Correct me if I am wrong.
> 
> devm_clk_get() obtained clock is released using devm_clk_release() which is
> just calling clk_put(). Which caller prepared or enabled the clock is not
> tracked. It's the responsibility of the caller.
> 

You're right. Then I need to check for this.

Hmm, I'm pretty sure I looked at what other drivers do. I think I'm not the
only one who forgets to call clk_disable_unprepare.

Regards,

	Hans



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