[libcamera-devel] IMX258 and speckled images

[Kieran Bingham]

Hi Dave,

Quoting Dave Stevenson via libcamera-devel (2022-06-22 11:34:16)
> Hi All.
> 
> A quick query as I'm aware that others on here are using the Sony IMX258 sensor.
> Are you using the sensor driver as-is from mainline[1], or does it need changes?

I think the Nautilus uses the IMX258. But as a ChromeOS device, the
driver should be expected to be as-is from mainline.

 
> A third party manufacturer has made an IMX258 module for the Pi[2],
> but we're getting dark speckles in the raw image, which we're guessing
> is down to PDAF pixel correction. The module manufacturer also
> believes that there may be versions of the module with and without
> PDAF pixels, which may well explain the issue.

I guess this might look like noise on the resulting image? or is it
fixed spots that look like broken pixels? (An image might help if
feasible).


> It seems that register 0x4e21 being set to 0x14 by the driver is the
> main cause, and the default of 0x10 gives good images. Of course
> register 0x4e21 isn't documented in any of the datasheets and appnotes
> I have from Sony. I have an enquiry in with them, but I wondered if
> others had seen similar issues, or might have documentation about that
> register.

Umang, can you confirm if this is the driver in use by the Nautilus?



> 
> Thanks
>   Dave
> 
> [1] https://github.com/torvalds/linux/blob/master/drivers/media/i2c/imx258.c
> [2] https://soho-enterprise.com/products/