media: i2c: imx214: Fix link frequency validation

media: i2c: imx214: Fix link frequency validation

The driver defines IMX214_DEFAULT_LINK_FREQ 480000000, and then
IMX214_DEFAULT_PIXEL_RATE ((IMX214_DEFAULT_LINK_FREQ * 8LL) / 10),
which works out as 384MPix/s. (The 8 is 4 lanes and DDR.)

Parsing the PLL registers with the defined 24MHz input. We're in single
PLL mode, so MIPI frequency is directly linked to pixel rate.  VTCK ends
up being 1200MHz, and VTPXCK and OPPXCK both are 120MHz.  Section 5.3
"Frame rate calculation formula" says "Pixel rate
[pixels/s] = VTPXCK [MHz] * 4", so 120 * 4 = 480MPix/s, which basically
agrees with my number above.

3.1.4. MIPI global timing setting says "Output bitrate = OPPXCK * reg
0x113[7:0]", so 120MHz * 10, or 1200Mbit/s. That would be a link
frequency of 600MHz due to DDR.
That also matches to 480MPix/s * 10bpp / 4 lanes / 2 for DDR.

Keep the previous link frequency for backward compatibility.

Acked-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: André Apitzsch <git@apitzsch.eu>
Fixes: 436190596241 ("media: imx214: Add imx214 camera sensor driver")
Cc: stable@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>