Processor CLKIN and CLKOUT pin functionality

[nija_mankodi]

Hi NXP team,

Please help to share functionality of processor pins CLKIN1/2 and CLKOUT1/2 (pins H27, J27, H26 and J26). These pins are open (with test point) in EVK also.

Where can we use these pins?

[nija_mankodi]

Hi NXP team,

Please resolve this query ASAP.

[gusarambula]

Hello Nija Mankodi,

I would like to confirm that you are referring to the signals of the i.MX8MM Processor. The CLKIN pins allow to feed the main clock instead of SYS_XTAL. If not in use it may be left floating.

The CLKOUT pins can be used to observe internal clocks on a testpoint.

My apologies for the lack of clarity on the documentation regarding these pins.
Regards,

[Aurelien_BOUIN]

Hello I am also interested in the answer of how to use it

I am trying to monitor some internal signal of the iMX8MM processor thanks to balls H26=>CLKOUT1 and J26=>CLKOUT2

From my understanding of the reference manual we need to change registers CCM_ANALOG_ANAMIX_PLL_MNIT_CTL 0x30360128 which is page 592 of RM 5.1.8.38 PLL Clock Output for Test Enable and Select Register

The problem is that I don't get any signal from those both pins when writing any value ...

My tests :

sudo memtool -32 0x30360128=0x1e1

What ever could be the "e" value replaced by anything there is still no signal at the output of CLKOUT1 H26 ball

The value is writen which I confirm in reading then the value :

sudo memtool -32 0x30360128 1
E
Reading 0x1 count starting at address 0x30360128

0x30360128:  000001E1

Thank you for your support

PS : I have updated imx-test to add imx8mm registers here : GitHub - aurelihein/imx-test: Official imx-test(https://source.codeaurora.org/external/imx/imx-test/... 

[fabio_estevam]

Hi Aurelien,

arch/arm64/boot/dts/freescale/fsl-imx8mm-evk.dts has an example of driving the CLKO1 pin to feed the OV5640 clock.

Basically all you need is to setup the IOMUX for the CLOK1 pin, select the correct parent (24MHz osc in this case) and pass it to the camera node.

Regards,

Fabio Estevam

[Aurelien_BOUIN]

Hi Fabio,

It seems that you are talking about the pin GPIO1_IO14 (ball : AC9)(unfortunately I don't have test point on this one)

BUT in this thread we are talking about balls H26=>CLKOUT1 and J26=>CLKOUT2

The only documentation I have in reference manual about those pins are :

Thank you for your support

Best regards,

Aurelien BOUIN

[rjm]

Perhaps you should try 0x1d1, 24 MHz input sysclock/2. This one cannot be absent...

I did it with u-boot command: nm.w 30360128 1d1

I also found clocks on ARM PLL and SYSPLL 1-3.

Please remind that for higher frequency output you should set FSEL_1_FAST_SLEW_RATE in SW_PAD_CTL_PAD_CLKOUT1 SW PAD Control Register