[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...?
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