Preempt-RT on i.mx8m plus

[ChrisChang1234]

Hi:

Refer to the document https://www.nxp.com/docs/en/user-guide/RTEDGEYOCTOUG_REV2.2.pdf,

I built 2 images to compare the effect. ( imx-image-multimedia)

One is the original yocto project, the other followed the introduction in chapter 7.

But I got some problems

1. Once the i.mx8mp runs with preempt-rt, a message shows after the system boot completely. 

    "imx-sdma 30bd0000.dma-controller: external firmware not found, using ROM firmware"   

    Is this a problem to my device?

    Once the message shows, the value of "max" in rt-test goes much higher. 

2. Using the rt-test tool to observe the latency.

    I run the 2 separate rt-test threads simultaneously,

    one is in (USB to RS232) terminal, the other is in weston GUI.

    The measured "MAX" values are diffrent. 

    Which one should I use?

3. And one other question, how to check the pre-empt-RT is properly run in my system?

    run "stress" program in background,

    and observe the 'max' values in rt-test.

    Is it a correct way to do this?  

[ChrisChang1234]

Hi:

Now my syste, deosn't pop the 'cannot load firmware' message.

And I run the rt-tsets,

there is no much diffrence in Max. field with running the pre-emt RT paches.

How do  I ensure the pre-emt RT is installed and executed properlyin my system?

[AldoG]

Hello,

For problems regarding imx-sdma 30bd0000.dma-controller: external firmware not found, using ROM firmware, please try the solution provided here:
https://community.nxp.com/t5/i-MX-Processors/Yocto-build-external-firmware-error/m-p/1227957/highlig...

Best regards,
Aldo.

[ChrisChang1234]

Hi:

After study the "solution",

=> 

1. I'm using i.mxp8m plus, I cannot find the firmware. 

   And there is no  "/lib/firmware/xxxx" path in my i.mx machine.

   Any idea for this?

2. It mentions, "include the firmware as a kernel module",

    How to di it?

    Any document to guide this?

[AldoG]

Hello,

1> If SDMA firmware is not found please try by manually add it, you may download using the following:

$ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/firmware-imx-8.14.bin
Execute and accept EULA and you'll get the i.MX SDMA firmware.

2> For this you may do the following:
$ bitbake linux-imx -c menuconfig
select: Drivers -> DMA Engine Support -> i.MX SDMA support  [M]

After this is done you may re-compile the image.

Best regards,
Aldo.

[ChrisChang1234]

Hi:

Thanks for your info.

But need for some more detail for this,

1. For the firmware, which folder should I insert it in?   

    Or I should create a new recipe for this?  How?

2. Finally I get the "i.MX SDMA support" item in menuconfig "device drivers -> DMA Engine support"

    and set it to "M"

    but in its help, it says it supports

           freescale i.mx25/3135 ...

    but no i.mx8m plus, Is it correct?

I put the "help.png" in the attachment.

[ChrisChang1234]

Hi AldoG:

Thanks, I'll try it.

And for question 2, 

I run 2 rt-test in teminals in USB-to-Serial and Weston GUI at the same time,

They shows different values in MAX-LATENCY.

Which one should I refer to?