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SubjectRe: [PATCH v2 1/3] dt-bindings: media: i2c: Add IMX290 CMOS sensor binding
Hi Russell,

On Tue, Aug 13, 2019 at 12:38:46PM +0100, Russell King - ARM Linux admin wrote:
> On Tue, Aug 06, 2019 at 06:39:36PM +0530, Manivannan Sadhasivam wrote:
> > +Required Properties:
> > +- compatible: Should be "sony,imx290"
> > +- reg: I2C bus address of the device
> > +- clocks: Reference to the xclk clock.
> > +- clock-names: Should be "xclk".
> > +- clock-frequency: Frequency of the xclk clock.
>
> Driver code:
>
> + ret = of_property_read_u32(dev->of_node, "clock-frequency", &xclk_freq);+ if (ret) {
> + dev_err(dev, "Could not get xclk frequency\n");
> + return ret;
> + }
> +
> + /* external clock must be 37.125 MHz */
> + if (xclk_freq != 37125000) {
> + dev_err(dev, "External clock frequency %u is not supported\n",
> + xclk_freq);
> + return -EINVAL;
> + }
>
> So, only 37125000 is supported - is that not worth mentioning in this
> description? Is this a hard requirement of the sensor? If so, why
> does it need to be mentioned in the DT binding?

The driver only supports a particular frequency, but the sensor is not
limited to that. Unfortunately this is not uncommon for camera sensors, for
the vendors often provide register settings for a given configuration only
(external clock frequency, number of CSI-2 lanes, CSI-2 bus frequency,
image cropping, binning etc.).

That still doesn't mean there are no alternative configurations for
different external clock frequencies, or that there could not be a driver
that was able to configure the sensor to use a given frequency.

--
Regards,

Sakari Ailus

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