[libcamera-devel] IMX258 and speckled images

[Laurent Pinchart]

On Thu, Jun 23, 2022 at 05:40:10PM +0100, Kieran Bingham via libcamera-devel wrote:
> 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).

Would it be possible to share sample images that display the issue ?

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

-- 
Regards,

Laurent Pinchart