JODY-W377 (Wi-Fi6) communication speed difference caused by i.MX8MQ specification difference

[hbjeong]

Hi NXP team,

I have a question about the communication test using JODY-W377 on i.MX8MQ and i.MX6Q.

The test conditions are

i.MX8MQ - AP mode
(Run iperf -s -u -i1)
i.MX6Q - Station mode
(Run iperf -c 192.168.1.20 -u -b500M -i1 -t 20)

Running the test as shown above will give the following results depending on the part specification of the i.MX8MQ.

Test 1
MIMX8MQ6DVAJZAA
Commercial 0~95 °C
Cortex-A53 CPU speed level : 1.5GHz
Wi-Fi6 Communication speed: Approx. 510Mbps

Test 2
MIMX8MQ6CVAHZAA
Industrial -40~105°C
Cortex-A53 CPU speed level : 1.3GHz
Wi-Fi6 Communication speed : Approx. 250Mbps

(Attach the log files for Test1 and Test2)

The i.MX6Q board is the same for both Test1 and Test2,
i.MX8MQ is the same board, only the AP (i.MX8MQ) is different.

Test1 : Commercial
Test2 : Industrial

If you remove each commercial and industrial AP (i.MX8MQ) and rework them on opposite boards, the symptoms are reversed.
The symptoms are reversed (the speed difference is reproduced depending on the AP).

I should get more than 500Mbps on the i.MX8MQ with industrial -40~105°C spec.
Please let me know if there is any other way to resolve this or if there is a way to test with different settings.

Kind regards.

[shaun_wu]

Hello @hbjeong 

Can you use 'mlanutl mlanX get_sensor_temp' to get chip temperature when throughput is low?

Best Regards

Shaun

[hbjeong]

Regardless of the specific temperature, if all conditions (including temperature) are the same, changing only the AP from MIMX8MQ6DVAJZAA to MIMX8MQ6CVAHZAA reduces the throughput from 500Mbps to 250Mbps.
If all conditions are the same and only the AP is changed, you will see the same behaviour as above.
This has been confirmed by reworking several boards and APs.
I recently received two MIMX8MQ6CVAHZAA from NXP's website and reworked them all, but the symptom is the same.

In conclusion, the commercial version of the AP is capable of 500Mbps performance,
The industrial version of the AP does not have 500Mbps performance.
Can you please explain this?

(Note that, JODY-W377 and i.MX8MQ are operating with PCIE interface.)

Best Regards

[shaun_wu]

Hello @hbjeong 

OK, I'm in progress to get a industrial chip and try on my side. Could you try to reduce consumer operation frequency to 1.3GHz then test again? You can reduce operation frequency in dtsi file:

Spoiler

        a53_opp_table: opp-table {
                compatible = "operating-points-v2";
                opp-shared;

                opp-800000000 {
                        opp-hz = /bits/ 64 <800000000>;
                        opp-microvolt = <900000>;
                        /* Industrial only */
                        opp-supported-hw = <0xf>, <0x4>;
                        clock-latency-ns = <150000>;
                        opp-suspend;
                };

                opp-1000000000 {
                        opp-hz = /bits/ 64 <1000000000>;
                        opp-microvolt = <900000>;
                        /* Consumer only */
                        opp-supported-hw = <0xe>, <0x3>;
                        clock-latency-ns = <150000>;
                        opp-suspend;
                };

                opp-1300000000 {
                        opp-hz = /bits/ 64 <1300000000>;
                        opp-microvolt = <1000000>;
                        opp-supported-hw = <0xc>, <0x4>;
                        clock-latency-ns = <150000>;
                        opp-suspend;
                };

                opp-1500000000 {
                        opp-hz = /bits/ 64 <1500000000>;
                        opp-microvolt = <1000000>;
                        opp-supported-hw = <0x8>, <0x3>;
                        clock-latency-ns = <150000>;
                        opp-suspend;
                };
        };

Best Regards

Shaun

[shaun_wu]

Hello @hbjeong 

In conclusion, the commercial version of the AP is capable of 500Mbps performance,
The industrial version of the AP does not have 500Mbps performance.

-->Can you confirm throughput is low when MIMX8MQ6CVAHZAA working in nominal temperature (25℃)? 

Best Regards

Shaun

[shaun_wu]

Hello @hbjeong 

Can you also share test result in sub 0℃ for test case1 and test case2? It is clear that issue is happends on host side. We want to check if it is Layout problem or chipest problem.

Best Regards

Shaun

[hbjeong]

We have tested it at -30℃, 0℃, 25℃, 50℃ using a temperature chamber and the results are the same as before.

Best Regards

[shaun_wu]

Hello @hbjeong 

I want to try on my side, could you share jody_w377_driver.sh? Or share steps you setup ap?

Best Regards

Shaun

[hbjeong]

Please find below a revised summary of our inquiry:

[Inquiry 1]
We have observed a difference in Wi-Fi 6 communication speeds between the Commercial and Industrial versions of the i.MX8MQ AP chip.

The primary differences between the two versions are the temperature specifications and the Cortex-A53 CPU clock speed (Commercial: 1.5GHz, Industrial: 1.3GHz).

In our tests, the Commercial version achieved a bandwidth of 500Mbps, while the Industrial version only reached 250Mbps, which is half the speed. We are curious if a 0.2GHz clock speed difference can cause such a significant performance discrepancy.

For reference, Wi-Fi communication between two i.MX6Q (1GHz) boards also resulted in a bandwidth of 500Mbps, so the CPU clock speed alone does not seem to fully explain this phenomenon.

We suspect other factors, such as the Wi-Fi 6 support features of the i.MX8M series or characteristics of the PCIE interface, might be contributing to the difference.

Could you provide a technical explanation from NXP on the root cause of the communication speed difference? Additionally, what recommendations would you make to improve product reliability in this context?

As briefly mentioned above, the Wi-Fi 6 interface is PCIE. Does the PCIE speed vary between the Commercial and Industrial versions?

[Inquiry 2]
The official operating temperature range for the Commercial version of the AP is 0~95°C, but we have found that it operates normally and can communicate at -30°C.

We believe that NXP may have conservatively specified the temperature range to ensure product stability.

Given that the actual operating temperature range is wider, indicating high product reliability, could you provide additional explanation regarding this aspect from NXP's perspective?

Thank you for your attention and we look forward to your response.

Best regards,

[shaun_wu]

Hello @hbjeong 

Could you provide a technical explanation from NXP on the root cause of the communication speed difference? Additionally, what recommendations would you make to improve product reliability in this context?

--> The Wi-Fi module have own 40MHz clock, which is not related to the host. The PCIe of two chip version is same. And the operation speed is 2.5GHz and 5GHz which is far higher than 500M. In addition, our pcie clock  frequency assigned by dts file is 10M; 100M; 250M, which is lower than 1.3GHz or 1.5GHz. So, it should not be limited by PCIe interface. 

Given that the actual operating temperature range is wider, indicating high product reliability, could you provide additional explanation regarding this aspect from NXP's perspective?

--> it is not recommended, in high pressure testing, the consumer chip may reboot or dump in non-supported environment. And in mass production, we cannot guarantee the stability ratio of chips.

Due to our test environment limitation, it is difficult to switch chip and test locally, I recommend you to use another industrial chip and try again, it might be a special case.

Best Regards

Shaun

[hbjeong]

Hello @shaun_wu

We have already reworked several boards and APs to verify.
The results were the same.

Best Regards

[hbjeong]

file attached.

Best Regards

[shaun_wu]

Hello @hbjeong 

The operation temperature of JODY-W377 (NXP 88w9098 inside) is -40°C to 85°C.

Best Regards

Shaun

[hbjeong]

We need to implement a communication speed of 500 Mbps at sub-zero temperatures.
However, as you can see in the text, 500 Mbps is only working on the Commercial (0-95 °C) version of the AP.

========================================
Test 1
MIMX8MQ6DVAJZAA
Commercial 0~95 °C
Cortex-A53 CPU speed level : 1.5GHz
Wi-Fi6 Communication speed: Approx. 510Mbps

Test 2
MIMX8MQ6CVAHZAA
Industrial -40~105°C
Cortex-A53 CPU speed level : 1.3GHz
Wi-Fi6 Communication speed : Approx. 250Mbps
========================================