topic Re: imx8mm pcie ref clock in i.MX Processors

imx8mm pcie ref clock

qssms — Fri, 06 Mar 2020 00:47:59 GMT

Hi,

I develop a board based on IMX8MM.

Board is var-som-mx8m-mini.

This board is connected to intel ethernet controller i210-AT chip.

then, this chip is connected to PCIE#A_REFCLK100M_N, PCIE#A_REFCLK100M_P.

But, I can not use this signal. clock output of this pin is nothing.

How to use a reference clock output for PCIE?

Is this possible to use?

Thanks.

Re: imx8mm pcie ref clock

igorpadykov — Sat, 07 Mar 2020 04:16:07 GMT

Hi seungmin

recommended to use external clock as described in Table 9. PCIe recommendations

i.MX 8M Mini Hardware Developer’s Guide

and follow i.MX8M Mini EVK schematic

i.MX 8M Mini Evaluation Kit LPDDR4 Design Files

Best regards
igor
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Re: imx8mm pcie ref clock

qssms — Mon, 09 Mar 2020 02:39:17 GMT

Thanks for your kind response.

I was receipt your board developer's guide. and it was very useful.

but, I want to know how to enable the PCIe clock.

default boot kernel image is disenabled PCIe ref clock output.

is there possible to use this pin to output clock by kernel edit?

Thanks.

shin

Re: imx8mm pcie ref clock

igorpadykov — Mon, 09 Mar 2020 05:42:39 GMT

this is not recommended, how ever one can try to enable it using

IOMUXC_GPR_GPR14 (check its description in Reference Manual).

Please look at function imx_pcie_enable_ref_clk() in imx6-pcie.c

pci-imx6.c\dwc\controller\pci\drivers - linux-imx - i.MX Linux kernel

clk driver

clk-imx8mm.c\imx\clk\drivers - linux-imx - i.MX Linux kernel

Best regards
igor

Re: imx8mm pcie ref clock

qssms — Tue, 10 Mar 2020 01:51:13 GMT

I know that is not recommended. but I want to know my schemetic is the right thing for just test.

I write further my question below.

1. my kernel version of i.MX8 mini is imx_4.14.98 2.0.0_ga. but your kernel version of the response function is imx_4.19.35_1.1.0. this function isn't matching my kernel version. how to edit in imx_4.14.98_2.0.0_ga?

2. I used the yocto project to i.MX8 mini. and use bitbake. is it possible to edit to use bitbake - menuconfig?

thanks

shin

Re: imx8mm pcie ref clock

igorpadykov — Tue, 10 Mar 2020 04:36:35 GMT

for L4.14.98 2.0.0 it is :

pci-imx6.c\dwc\pci\drivers - linux-imx - i.MX Linux kernel

Best regards
igor

Re: imx8mm pcie ref clock

marcelziswiler — Thu, 18 Feb 2021 20:35:06 GMT

> this is not recommended

What exactly do you mean? Supposedly, this has been validated by NXP, not?