linux-kernel - Re: [PATCH v4 2/2] ARM: imx6plus: enable internal routing of clk_enet

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Date:   Mon, 29 Jun 2020 10:09:59 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Shawn Guo <shawnguo@...nel.org>, Fugang Duan <fugang.duan@....com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] ARM: imx6plus: enable internal routing of
 clk_enet_ref where possible

Hi Sven,

On Thu, Jun 25, 2020 at 11:01 AM Sven Van Asbroeck <thesven73@...il.com> wrote:
>
> On imx6, the ethernet reference clock (clk_enet_ref) can be generated
> by either the imx6, or an external source (e.g. an oscillator or the
> PHY). When generated by the imx6, the clock source (from ANATOP)
> must be routed to the input of clk_enet_ref via two pads on the SoC,
> typically via a dedicated track on the PCB.
>
> On an imx6 plus however, there is a new setting which enables this
> clock to be routed internally on the SoC, from its ANATOP clock
> source, straight to clk_enet_ref, without having to go through
> the SoC pads.
>
> Board designs where the clock is generated by the imx6 should not
> be affected by routing the clock internally. Therefore on a plus,
> we can enable internal routing by default.
>
> Signed-off-by: Sven Van Asbroeck <TheSven73@...il.com>

I have tested this series on an imx6qp sabresd and unfortunately, it
breaks Ethernet as I can no longer get an IP address from the DHCP
server.

Without this series, IP address can normally be retrieved.

Therefore I suggest to create a device tree property for this feature
and only enable it when such device tree property is present.