Re: [PATCH v14 00/15] phy: Add support for Lynx 10G SerDes

[Vladimir Oltean <vladimir.oltean@xxxxxxx>]

On Wed, Apr 26, 2023 at 10:50:17AM -0400, Sean Anderson wrote:
> > I need to catch up with 14 rounds of patches from you and with the
> > discussions that took place on each version, and understand how you
> > responded to feedback like "don't remove PHY interrupts without finding
> > out why they don't work"
> 
> All I can say is that
> 
> - It doesn't work on my board
> - The traces are on the bottom of the PCB
> - The signal goes through an FPGA which (unlike the LS1046ARDB) is closed-source

I don't understand the distinction you are making here. Are the sources
for QIXIS bit streams public for any Layerscape board?

> - The alternative is polling once a second (not terribly intensive)

It makes a difference to performance (forwarded packets per second), believe it or not.

> 
> I think it's very reasonable to make this change. Anyway, it's in a separate
> patch so that it can be applied independently.

Perhaps better phrased: "discussed separately"...

> > Even if the SERDES and PLL drivers "work for you" in the current form,
> > I doubt the usefulness of a PLL driver if you have to disconnect the
> > SoC's reset request signal on the board to not be stuck in a reboot loop.
> 
> I would like to emphasize that this has *nothing to do with this driver*.
> This behavior is part of the boot ROM (or something like it) and occurs before
> any user code has ever executed. The problem of course is that certain RCWs
> expect the reference clocks to be in certain (incompatible) configurations,
> and will fail the boot without a lock. I think this is rather silly (since
> you only need PLL lock when you actually want to use the serdes), but that's
> how it is. And of course, this is only necessary because I was unable to get
> major reconfiguration to work. In an ideal world, you could always boot with
> the same RCW (with PLL config matching the board) and choose the major protocol
> at runtime.

Could you please tell me what are the reference clock frequencies that
your board provides at boot time to the 2 PLLs, and which SERDES
protocol out of those 2 (1133 and 3333) boots correctly (no RESET_REQ
hacks necessary) with those refclks? I will try to get a LS1046A-QDS
where I boot from the same refclk + SERDES protocol configuration as
you, and use PBI commands in the RCW to reconfigure the lanes (PLL
selection and protocol registers) for the other mode, while keeping the
FRATE_SEL of the PLLs unmodified.