On 03-09-2025 08:17, Mike Looijmans wrote:
On 02-09-2025 19:29, Maxime Ripard wrote:
On Mon, Sep 01, 2025 at 04:29:01PM +0200, Mike Looijmans wrote:
+ ti,retimer-threshold-hz:
+ minimum: 25000000
+ maximum: 600000000
+ default: 200000000
+ description:
+ Cross-over point. Up until this pixel clock frequency
+ the chip remains in the low-power redriver mode. Above
+ the threshold the chip should operate in retimer mode.
Why should anyone want to tune this at the firmware level?
It's a board property. You'd set this based on the hardware you've soldered
on. If your clock and serdes are good quality, there's no need for the chip
to be in retimer mode (it will consume more power and actually make the
signal worse). At higher speeds, that situation may change, hence the need
for a way to describe that. The chip has a similar function built in, but
with only 2 choices of cross-over point.
To tune these parameters (retimer, equalizer), you'll probably have to take
your equipment to a test facility (like we did). It's not something that
end-users would want to tune themselves.
Most of these settings can also be done using pin strapping. I guess it'd be
helpful if I added that to the description.
Looking back at the datasheet - once you enable the I2C interface of the pin,
many of the pinstrapping options are no longer available (such as slew-rate,
dvi/hdmi mode, equalizer and termination). The devicetree properties allow
these settings to be applied again.
...
M.
