topic Re: Wrong MDC frequency RW612 frdm_rw612 in Zephyr Project

Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Mon, 03 Mar 2025 09:28:50 GMT

Hi all!

During development I encountered Ethernet connection stability issues. After some investigation using both rw612 custom board and frdm_rw612, it occured that frequency on MDC pin was wrong. Instead of 2.5MHz, it is 13 MHz. As Ethernet module ksz8081 allows up to 10 MHz MDC frequency, it is just luck that eth is working stable on frdm_rw612 (you can flash any eth sample from Zephyr and see that frequency on MDC pin on frdm_rw612 is 13 MHz)

Getting deeper, it seems that issue root cause is in ethernet MSCR register, which for MII_SPEED calculation uses fixed 50MHz clock value. I found it in Zephyr under CLOCK_GetTddrMciEnetClkFreq(void) function in mcux/mcux-sdk/devices/RW612/drivers/fsl_clock.c.

When i calculate this register value using M33 processor frequency (260 MHz), then I see correct MDC frequency - 2.5MHz.

According to RW612 datasheet frequency in code (50 MHz) seems to be correct, but in reality it uses 260 MHz clock as reference to calculations.

Initially I changed returned value from CLOCK_GetTddrMciEnetClkFreq to 260 MHz, but I'm not sure that it won't influence on other part of code but it now works.

Could You please confirm that issue exists and help me where to fix it?

Re: Wrong MDC frequency RW612 frdm_rw612

Ricardo_Zamora — Mon, 03 Mar 2025 21:45:59 GMT

Hello,

Hope you are doing well. Could you please give us more details about your setup?

What SDK version are you using? Did you try with the ethernet example from the SDK?

How are you measuring this with the FRDM?

Best Regards,

Ricardo

Re: Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Tue, 04 Mar 2025 10:50:31 GMT

Hello Ricardo,

With our product we are working on Zephyr 3.7 but to be sure that this issue is reproducible I set up Zephyr 4.1.0.rc3, it uses zephyrSdk 0.17.0 and in west.yml I see that it points to HAL NXP rev. 9dc7449014a7380355612453b31be479cb3a6833 (https://github.com/zephyrproject-rtos/hal_nxp/commits/9dc7449014a7380355612453b31be479cb3a6833).

I build dhcpv4 example from Zephyr samples using the following command:

west build -b frdm_rw612 samples/net/dhcpv4_client/ -p

After flashing, I see on console that this example starts correctly. I measured frequency on GPIO56 (exactly on R31 on frdm_rw612 board). Please see image from frdm_rw612 schematic:

Measured frequency is ~13 MHz. According to ksz8081 datasheet it shall not exceed 10MHz and optimal conditions is if this frequency is 2.5 MHz:

Looking into MSCR register, it seems to have correct value, but in reality it has to be recalculated using 260 MHz frequency, not 50 MHz. Because of that MSCR MII_SPEED is 13MHz instead of 2.5MHz and MSCR HOLDTIME is set to 0 causing connection issues.

I've made some work-around in enet devicetree, but it can't be like that. Using the following method leaves HOLDTIME value wrong and there are still some communication issues.

I didn't tried eth example from mcuexpresso as we are using Zephyr for our development

Re: Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Tue, 04 Mar 2025 11:16:04 GMT

Here I attach measuring MDC frequency with changed CLOCK_GetTddrMciEnetClkFreq to 260 MHz:

Re: Wrong MDC frequency RW612 frdm_rw612

Ricardo_Zamora — Thu, 06 Mar 2025 16:41:10 GMT

Hello,

I know that you are using Zephyr, but could you please help us check if this issue is also present when using the MCUXpresso SDK?

I also will be checking the Zephyr example in the meantime.

Regards,

Ricardo

Re: Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Thu, 06 Mar 2025 16:56:35 GMT

Hi,

No problem, I've flashed frdmrw612_enet_txrx_transfer sample using MCUXpresso IDE 24.9.25 and here everything seems to work fine, measured frequency on MDC pin is 2.5 MHz

Re: Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Thu, 06 Mar 2025 18:09:40 GMT

It seems that in MCUxpresso sample 260 MHz frequency is being used to calculate MSCR register values:

Re: Wrong MDC frequency RW612 frdm_rw612

Maciej_Jj — Mon, 17 Mar 2025 07:38:03 GMT

Hello Ricardo,

are there any updates?

Re: Wrong MDC frequency RW612 frdm_rw612

pavel_krenek — Thu, 03 Apr 2025 08:16:45 GMT

Hello Maciej,

I was going through all your inputs and yes you find the relevant issue which need to be fixed. As a quick fix you can change the value of CLOCK_MHZ as you did to 260MHz in the function CLOCK_GetTddrMciEnetClkFreq. You can continue work and we will work on the update on GitHub repository.

Best regards,
Pavel Krenek