topic Re: 25MHz clock from i.MX 6 GPIO16 stops during Linux kernel boot in i.MX Processors

25MHz clock from i.MX 6 GPIO16 stops during Linux kernel boot

mahi — Wed, 04 Nov 2015 08:54:26 GMT

Hi community,

I am using a 25MHz clock generated by i.MX6 for my ethernet PHY. The clock output is enabled in u-boot which works just fine. But during the startup of the Linux kernel, this clock "disappears" for some seconds and when startup is almost finished, it recovers.

I think the clock is restarted in imx6q_clocks_init (clk-imx6q.c) but I cannot find where and why it is stopped.

Can someone give me a hint, where my clock might get disabled?

Unfortunately I couldn't manage to set up a working debugging solution for the kernel yet - apparently my J-Link does not like the i.MX6, but this is a different story.

Best regards Martin

Re: 25MHz clock from i.MX 6 GPIO16 stops during Linux kernel boot

mahi — Fri, 06 Nov 2015 11:50:26 GMT

I found where the clock is stopped... fec_probe (in fec_main.c) calls fec_enet_clk_enable(ndev, false); to disable the clocks.

But I still can't figure out why this is done...

Re: 25MHz clock from i.MX 6 GPIO16 stops during Linux kernel boot

alejandrolozan1 — Tue, 10 Nov 2015 21:11:18 GMT

Hi,

Are you getting some kind of problem because of this?

What you mentioned seems to be related to this patch, but not su sure yet.

[PATCH v5] net: fec: Ensure clocks are enabled while using mdio bus

Re: 25MHz clock from i.MX 6 GPIO16 stops during Linux kernel boot

mahi — Wed, 11 Nov 2015 12:24:09 GMT

Hi Alejandro,

actually this is not a problem.

I suspected the missing clock to be the reason why the KSZ9031 on my board was not found. In the end the real reason was the power supply of the PHY being disabled due to a missing entry in the device tree...

Best Regards

Martin