Use internal clock for PCIE in IMX8MQ

[jemish_1990]

Hi All,

We are working product based on IMX8MQ (MIMX8MQ6DVAJZAA) processor.

Kernel version: 4.14.98

Till now we were using PCI clock generator chip for PCI host. But now due to shortage of this chip we decided to use internal clock generated by IMX8MQ for PCI. But we are not able to make it work.

We didn't observe PCI clock generated on oscilloscope and we are not able to detect WIFI module.

To use internal clock for PCI we did following configuration.

&pcie0{
            pinctrl-names = "default";
            pinctrl-0 = <&pinctrl_pcie0>;
            disable-gpio = <&gpio3 7 GPIO_ACTIVE_LOW>;
            reset-gpio = <&gpio3 9 GPIO_ACTIVE_LOW>;
            ext_osc = <0>;
            hard-wired = <1>;
            status = "okay";
};

But it's not helping. Any suggestion or direction is appreciated.

Thanks,

Jemish

[jemish_1990]

Hi Dhruvit,

Thanks for you answer.

We understand that it's recommended to use external clock source for PCI. That's the reason we have used it till now in our products. But recently due to chip shortage issue we want to avoid usage of external clock source.

My question is why it's not working in IMX8MQ. There is a provision in driver either to use internal or external clock source then it should work in both cases. Is there any additional configuration that I need to take care of? Please suggest.

Also we made a product in 2016 based on IMX6Q. In which we use internal clock source for PCI and it's worked very well. So it should work in IMX8MQ also. And we are still using same PCIE host driver for both processors so it must work in both of the cases.

Thanks,

Jemish

[Dhruvit]

Hi @jemish_1990,

Could you please provide me with the kernel logs?

Best Regards,
Dhruvit.

[Dhruvit]

Hi @jemish_1990,

Please note that it is recommended to use an external clock as described in "Table 10 PCIe recommendations" of the Hardware Developer's guide.

Best Regards,
Dhruvit.