Re: [PATCH 07/23] media: atomisp: gc0310: Add link-frequency and pixelrate controls

[Andy Shevchenko <andy@kernel.org>]

On Sat, May 17, 2025 at 01:40:50PM +0200, Hans de Goede wrote:
> Add support for the pixelrate control as expected by libcamera,
> while at it also add the link-frequency control.

...

> +/*
> + * The actual PLL output rate is unknown, the datasheet
> + * says that the formula for the frame-time in pixels is:
> + * rowtime = win-width + hblank + sh-delay + 4
> + * frametime = rowtime * (win-height + vblank)
> + * Filling this in and multiplying by 30 fps gives:
> + * pixelrate = (660 + 178 + 42 + 4) * (498 + 27) * 30 = 13923000
> + */
> +#define GC0310_PIXELRATE			13923000

Why not utilise the preprocessor to calculate the above?
I mean we can define an arithmetic expression instead of the result
(which is mentioned in the comments anyway).

...

> +/* single lane, bus-format is 8 bpp, CSI-2 is double data rate */
> +#define GC0310_LINK_FREQ			(GC0310_PIXELRATE * 8 / 2)

Hmm... I believe it won't be ever the case, but still the Q here is
if we expect rounded up value? In such a case perhaps BITS_TO_BYTES()
would make sense. OTOH the format theoretically can be not only 8bpp
in some cases, but let's say 9bpp, that macro wouldn't help then.

-- 
With Best Regards,
Andy Shevchenko