[EXT] Re: [PATCH v4 2/2] ARM: imx6plus: enable internal routing of clk_enet_ref where possible

Sven Van Asbroeck thesven73 at gmail.com
Tue Jun 30 11:23:45 EDT 2020

Andy, Fabio,

On Tue, Jun 30, 2020 at 2:36 AM Andy Duan <fugang.duan at nxp.com> wrote:
> Sven, no matter PHY supply 125Mhz clock to pad or not,  GPR5[9] is to select RGMII
> gtx clock source from:
> - 0 Clock from pad
> - 1 Clock from PLL
> Since i.MX6QP can internally supply clock to MAC, we can set GPR5[9] bit by default.

That's true. But on the sabresd I notice that the PHY's ref_clk output
is from CLK_25M.
The default ref_clk freq for that PHY is 25 MHz, and I don't see anyone change
the default in the devicetree. I also see that a 25 MHz crystal is fitted, which
also suggests 25 Mhz output.

On the imx6, the default ref_clk frequency from ANATOP is 50Mhz. I don't
see anyone change that default in the devicetree either.

So is it possible that, when we switch GPR5[9] on, the external 25MHz clock
is replaced by the internal 50MHz clock? If so, I'm not sure it'll work...?

More information about the linux-arm-kernel mailing list