Re: [PATCH] ARM: mach-imx6q: add ksz9131rn_phy_fixup

Ahmad Fatoum
2020-03-06T11:14:31Z

Hello Philippe,

On 3/6/20 10:46 AM, Philippe Schenker wrote:
> Hi Andrew and Ahmad, thanks for your comments. I totally forgot about
> those more specific phy-modes. But just because none of our driver
> supports that. Either the i.MX6 fec-driver as well as the micrel.c PHY
> driver supports this tags.
> What do you guys suggest then how I should implement that skew stuff?

I think implementing them in the Micrel driver would make sense.
When more specific skews are supplied, these are used.
If not, the rgmii_[tx]?id applies the appropriate timings for length matched
lines. Device trees matching your use case will then only have to specify
rgmii-txid.

> The problem is that i.MX6 has an asynchronic skew of -100 to 900ps only
> enabling the PHY-delay on TXC and RXC is not in all cases within the
> RGMII timing specs. That's why I implemented this 'weird' numbers.

I am not too well-versed with this. What's an asynchronic skew?
A non-deterministic internal delay..? So, you try to be as accurate as
possible, so the skew is within the acceptable margin?

Cheers
Ahmad

>
> Philippe
>

--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |