Re: [PATCH] media: i2c: imx219: Add support for 'clock-frequency' parsing

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Hi,

On 24/02/2025 13:54, Mehdi Djait wrote:
> Hi Sakari,
> 
> On Mon, Feb 24, 2025 at 09:42:12AM +0000, Sakari Ailus wrote:
>> Hi Mehdi,
>>
>> On Mon, Feb 24, 2025 at 08:59:34AM +0100, Mehdi Djait wrote:
>>> Hi Laurent,
>>>
>>> On Mon, Feb 24, 2025 at 01:06:49AM +0200, Laurent Pinchart wrote:
>>>> Hi Mehdi,
>>>>
>>>> Thank you for the patch.
>>>>
>>>> On Thu, Feb 20, 2025 at 04:49:09PM +0100, Mehdi Djait wrote:
>>>>> Make the clock producer reference lookup optional
>>>>>
>>>>> Add support for ACPI-based platforms by parsing the 'clock-frequency'
>>>>> property when no clock producer is available
>>>>>
>>>>> Signed-off-by: Mehdi Djait <mehdi.djait@linux.intel.com>
>>>>> ---
>>>>>   drivers/media/i2c/imx219.c | 14 ++++++++++++--
>>>>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
>>>>> index 2d54cea113e1..a876a6d80a47 100644
>>>>> --- a/drivers/media/i2c/imx219.c
>>>>> +++ b/drivers/media/i2c/imx219.c
>>>>> @@ -1103,12 +1103,22 @@ static int imx219_probe(struct i2c_client *client)
>>>>>   				     "failed to initialize CCI\n");
>>>>>   
>>>>>   	/* Get system clock (xclk) */
>>>>> -	imx219->xclk = devm_clk_get(dev, NULL);
>>>>> +	imx219->xclk = devm_clk_get_optional(dev, NULL);
>>>>>   	if (IS_ERR(imx219->xclk))
>>>>>   		return dev_err_probe(dev, PTR_ERR(imx219->xclk),
>>>>>   				     "failed to get xclk\n");
>>>>>   
>>>>> -	imx219->xclk_freq = clk_get_rate(imx219->xclk);
>>>>> +	if (imx219->xclk) {
>>>>> +		imx219->xclk_freq = clk_get_rate(imx219->xclk);
>>>>> +	} else {
>>>>> +		ret = fwnode_property_read_u32(dev_fwnode(dev),
>>>>> +					       "clock-frequency",
>>>>> +					       &imx219->xclk_freq);
>>>>> +		if (ret)
>>>>> +			return dev_err_probe(dev, ret,
>>>>> +					     "failed to get clock frequency");
>>>>> +	}
>>>>> +
>>>>
>>>> This doesn't seem specific to the imx219 driver. Could you turn this
>>>> into a generic V4L2 sensor helper that would take a struct device and a
>>>> clock name, and return the frequency, either retrieved from the clock,
>>>> or from the clock-frequency property as a fallback ?
>>>>
>>>> Some drivers will also need to control the clock, so the clock should
>>>> probably be returned too.
>>>>
>>>
>>> Yes, I saw that many sensor drivers have the same issue.
>>>
>>> I will try to make it into a generic V4L2 helper and send the patches.
>>
>> There are other such functions in drivers/media/v4l2-core/v4l2-common.c.
>> Perhaps this is where the new helper could be located as well?
>>
> 
> I was thinking about drivers/media/v4l2-core/v4l2-fwnode.c but if
> v4l2-common.c is more appropriate we can go with that.

I admit I have no clue about ACPI, but why is this v4l2 specific? Why 
doesn't clock framework do this for us?

  Tomi