topic Re: FlexRAM and Linker Problem in i.MX RT Crossover MCUs

FlexRAM and Linker Problem

david_huwyler — Thu, 14 Nov 2019 09:03:21 GMT

I want to run an application on a i.mx rt1052 with the following RAM config:

DTCM: 256k, ITCM: 128k, OC: 128k (default values: DTCM: 128k, ITCM: 128k, OC: 256k)

I want to reconfigure the FlexRAM at runtime, not with the fuses...

I tired the SDK example evkbimxrt1050_flexram_ram_allocate which works fine. In this example, the memory details in the Project properties (Linker settings) are configured to the default values of the FlexRAM, not the values to which the RAM is finally reconfigured in code. This way i can only use the default RAM space at compiletime, because otherwise the linker complains (not enough space in RAM).

But as soon as i reconfigure the Memory details in the Project Property window to fit my needs, the linker is happy, but I get debugger errors at startup (not all RAM accessible). Because the RAM is not jet reconfigured (no code is executed jet).

Any Idea how to get around this problem?

Some infos:

I need the DTCM for heap memory (200k)

I tried different debugging probes (J-Link & LPC-Link2)

IDE: MCUExpresso

Re: FlexRAM and Linker Problem

kerryzhou — Fri, 15 Nov 2019 08:26:02 GMT

Hi David Huwiler ,

Do you have read this flexRAM application note?

https://www.nxp.com/docs/en/application-note/AN12077.pdf

If not, please read it at first, it may useful to your question.

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Wed, 20 Nov 2019 06:22:41 GMT

Thanks for your answer Kerry.

Yes i read the mentioned document. But as far is i saw there is no information about my problem in the AN12077.

Dave

Re: FlexRAM and Linker Problem

kerryzhou — Wed, 20 Nov 2019 09:13:04 GMT

Hi David Huwiler,

Thanks for your updated information.

You said: but I get debugger errors at startup (not all RAM accessible).

Could you also give me a screenshot about it, I will find time to test your situation, and give you reply later.

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Thu, 21 Nov 2019 07:36:48 GMT

Sure:

I changed the Linkerfile Memorymap to DTCM: 256k, ITCM: 128k, OC: 128k:

(I use a seeed studio arch mix board with 8M qspi flash)

Now i set a breakpoint at the 1. executed Codeline in the startup code and start the debugger. The debugging actually works until now:

If I now do a "step into (F5)" the following error occurs:

Re: FlexRAM and Linker Problem

kerryzhou — Fri, 22 Nov 2019 06:17:32 GMT

Hi David Huwiler

Please upload your modified project directly, I will help you to check it on my side.

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Sun, 24 Nov 2019 08:43:57 GMT

Ok project is attached.

But its the same with any project. As soon as i change values in the linker memory section to non default ones...

Dave

Re: FlexRAM and Linker Problem

kerryzhou — Tue, 26 Nov 2019 10:06:36 GMT

Hi David Huwiler,

I have a MIMXRT1050-EVKB which is using the QSPI, and I also test it, even the simplest led_blinky project.

I can reproduce the problem, totally the same as you.

So, the linker file still need to be the default configuration.

But how to modify the linker file after the RAM reconfiguration, I need to check it with our MCUXpresso IDE team, just let our IDE expert to check whether there has some good method to process it.

After I get the valuable information, I will let you know.

Please keep patient, thanks a lot for your understanding.

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

kerryzhou — Fri, 29 Nov 2019 07:59:30 GMT

Hi David Huwiler and Takashi Kashiwagi,

After checking with our MCUXpresso IDE expert, the following workaround may help you:

---------------------------------------------------------------------------------

1 - Moving memory 'under the feet' of a running application is very dangerous, and should only be attempted if the user really understands how their application is using memory. Particularly for Stack and initialised variables.

This is especially true when you consider how flexRAM actually works. If the sizes of regions is changed, the new region may not contains any of the old RAM blocks.

Making any changes i main() is really too late, they should be made within the Startup code before any other action.

2 Describing a memory view for application generation that does not actually match the target (at the time debug is performed) is also very dangerous and can lead to the sort of problem you report,

A way to work around this would be to make use of a LinkServer Connect Script to setup the FlexRAM - the example below actually restores the default values but could be changed to set the new values required.

360 REM ====== Configure FlexRAM ======

370 print "Configure FlexRAM for 256KB OC RAM, 128KB I-TCM, 128KB D-TCM"

380 REM TCM CTRL Poke 0x400B0000 - to force RAM clocking and set wait states = b100

390 Poke32 this 0x400B0000 0x4

400 REM IOMUXC_GPR17 0x400AC044 - this sets bitfield allocation of FlexRAM 32KB banks to OC 256KB b01, I 128KB b11, D 128KB b10

410 Poke32 this 0x400AC044 0x5555FFAA

420 REM IOMUXC_GPR16 0x400AC040 - this sets enables for I and DTCM and the source of the TCM config = 0x200007

430 Poke32 this 0x400AC040 0x200007

440 print "Finished"

450 REM ===============================

The connect script can then be referenced within the projects LinkServer launch configuration.

Note: this will only work with LinkServer/CMSIS DAP debug.

If this is done, then the project can be configured using the projects MCU memory configuration to look something like this:

The result will be that the Image and the target memory will match for debug operations.

If the project memory changes are made within the startup file, the image should also power up correctly (without debug tools).

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So, if you have time, you can try the item 2 workaround, but just as our expert said, don't modify the flexRAM in the main, if your project really want to reconfigure the flexRAM, I think, if you can, it's better to configure the efuse at first, then create the related project.

Wish it helps you!

Any updated information, please kindly let me know.

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Wed, 04 Dec 2019 05:50:53 GMT

Hi Kerry Zhou

Thanks for your effort!

I tried the workaround you suggested.

Startup Code:

Linkserver Connect Script:

And it works as long as I start the target with the debugger attached.
If I start the target without the debugger, the application crashes.
As far as i can see, i do the same tings in the startup code, as in the Linkserver Script.

Any idea why it dosnt work without the debugger?

Re: FlexRAM and Linker Problem

kerryzhou — Wed, 04 Dec 2019 06:32:05 GMT

Hi David Huwiler,

I will test your situation with and without debugger, and updated information from my side, I will let you know.

Please wait patiently!

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

kerryzhou — Wed, 04 Dec 2019 11:28:12 GMT

Hi David Huwiler,

I have reproduced your problems, I will do more research, please wait patiently, thank you!

Have a great day,
Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Thu, 19 Dec 2019 15:50:44 GMT

Hi Kerry. Do you have any news regarding this issue?

Re: FlexRAM and Linker Problem

kerryzhou — Fri, 20 Dec 2019 03:08:05 GMT

Hi David,

So sorry for my later reply.

I get some information from our internal expert side, but I still don't have time to test it.

Please follow this suggestion, and test it on your side at first.

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So the basic question is - why does a system work under debug but fail on Power On Reset. The answer turns out to be a stack access performed by the ResetISR function before the flexRAM reconfigure is performed. See the disassembly of the ResetISR function...

00000000 <ResetISR>:

0: b510 push {r4, lr} // this stack access causes a fault

2: b672 cpsid i

4: 4b1a ldr r3, [pc, #104] ; (70 <ResetISR+0x70>)

6: 6b9a ldr r2, [r3, #56] ; 0x38

8: f442 0210 orr.w r2, r2, #9437184 ; 0x900000

c: 639a str r2, [r3, #56] ; 0x38

e: 4a19 ldr r2, [pc, #100] ; (74 <ResetISR+0x74>)

10: 645a str r2, [r3, #68] ; 0x44

12: 6c1a ldr r2, [r3, #64] ; 0x40

14: f042 0207 orr.w r2, r2, #7

18: 641a str r2, [r3, #64] ; 0x40

1a: 2300 movs r3, #0

1c: e000 b.n 20 <ResetISR+0x20>

1e: 4613 mov r3, r2

The very first instruction (at the entry point of the application) is a push to the stack - and at this point, put the memory in place for the first stack access.

There are a number of potential fixes to this problem.

1 - you could re-write the resetISR function in assembler

2 - you could set the fuses with the FlexRAM settings

3 - or you could leave the project memory configuration for the Stack to be in available memory (for the very first push) and then make a change to the new value. This first push is not necessary since we will never return from this function.

So - if the project memory is left like this:

You can then simply poke a new SP value. I tested this with the code as below:

My test code fragment:

__attribute__ ((section(".after_vectors.reset")))

void ResetISR(void) {

// Disable interrupts

__asm volatile ("cpsid i");

IOMUXC_GPR->GPR14 |= (9 << 20);

IOMUXC_GPR->GPR17 = 0x55FFAAAA;

IOMUXC_GPR->GPR16 |= 7;

__asm volatile ("mov r12, #0x20000000"); // here I reset the stack to the value I wanted at 0x20040000

__asm volatile ("orr r12, #0x40000");

__asm volatile ("mov sp, r12");

This asm code puts the Stack at 0x2004000 after the FlexRAM memory has been set correctly.

This is a bit 'nasty' and I think we need to investigate a better solution to this problem. I will raise a Jira to investigate the issue of ResetISR pushing data to the stack.

Please confirm that this 'fix' also works in your environment.

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Please help to check it, whether it works.

When I have time, I will also test it.

Any test result from yourside, please kindly let me know.

BTW, please note, when you divide the ITCM DTCM size, you need to meet the following demand:

The Arm Cortex-M7 specifications require the size of ITCM/DTCM to be a power-of-two number, which can conflict with the FlexRAM configuration capability (see configurations 7, 10, 11 in Table 1).

AN12077.

Have a great day,

Kerry

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Re: FlexRAM and Linker Problem

david_huwyler — Thu, 09 Jan 2020 08:43:43 GMT

Hi Kerry.

Thanks a lot for your effort.

I tried your potential fix number 3:

No success. Same as without the extra lines.

I dont want to burn the flexram fuses so fix number 2 dosnt suit my needs.

So is the only solution for me to rewrite the resetIST in assembler?

Regards,

Dave

Re: FlexRAM and Linker Problem

kerryzhou — Tue, 14 Jan 2020 11:19:30 GMT

Hi David Huwiler,

Thanks for your updated information.

I will contact with our IDE expert, and seek more help.

Any updated information from my side, I will let you know.

Really thanks so much for your patience.

Best Regards,

Kerry

Re: FlexRAM and Linker Problem

jackking — Sat, 22 Feb 2020 16:55:40 GMT

Is there any update on this?

I have the exact same issue. I am trying to set DTCM to 512k, with my stack located in DTCM.

The ASM flexRAM settings work, but the program will crash on entry into ResetISR if the linker is configured with 512k DTCM in the project

My DTCM usage is greater than the default, so the linker will error if I set the project to the default memory.

Re: FlexRAM and Linker Problem

jackking — Sat, 22 Feb 2020 17:05:11 GMT

I was able to change the project to locate stack at the beginning of the DTCM memory section instead of the default at the end.

This allows the stack to be used by ResetISR in a valid memory range before the FlexRAM is reconfigured.

Re: FlexRAM and Linker Problem

kerryzhou — Mon, 24 Feb 2020 01:58:47 GMT

Hi Jack King,

I didn't get the feedback anymore.

But, just as our IDE expert said:

2 - you could set the fuses with the FlexRAM settings

This maybe the useful way if you really want to modify the flexRAM in your product.

But, you said your program also have problems, you need to modify the script, please check the reply on on Nov 29, 2019 12:59 AM.

Now, the mainly problem is download and debug OK, POR has problems, so we still recommend the customer to use the fuse modify, it will be more useful.

Best Regards,

Kerry

Re: FlexRAM and Linker Problem

jackking — Mon, 24 Feb 2020 03:22:27 GMT

Kerry,

Please see my update above... moving the stack to the beginning of the memory range fixes my issue.