Accessing global memory ("devmem" on DSP)

Markus Grunwald

Expert 2060 points

Hello,

To access an FPGA that's memory mapped to our integra, I can use devmem (or something simlar) on the ARM side.

# devmem 0x20000150 32
0x000001DC

That reads 32 bits from 0x20000150, where 0x20000000 is the pci memory base. Now I thought that accessing this memory from the integras DSP would be easy, since it has a 1:1 memory mapping. But a look at CCS's memory window at 0x20000000 proved me wrong....

How can I access this memory from the DSP?

TIA

Markus

over 14 years ago

0 MarcPyne over 14 years ago

TI__Mastermind 25055 points

Markus,

Please refer to the C674x Memory Map and the L3 Master/Slave Connectivity table in the datasheet to determine the DSP's connectivity.

Regards,
Marc

0 Markus Grunwald over 14 years ago in reply to MarcPyne

Expert 2060 points

Hello Marc,

"2.9.5 C674x Memory Map" of SPRS680A tells me, that the range I'm interested in (starting at 0x20000000) has to be accessed via the DEMMU. "Table 5-1. L3 Master/Slave Connectivity" of the same document tells me simlar. But I am stuck again: how do I configure this DEMMU? It seems to be not too well documented. I still have no Idea how to access this memory... Could you please explain a bit more detailed?

Many thanks,

Markus

0 MarcPyne over 14 years ago in reply to Markus Grunwald

TI__Mastermind 25055 points

Markus,

Does the System MMU section of Chapter 1 of the device TRM have the information that you need?

Regards,
Marc

0 Markus Grunwald over 14 years ago in reply to MarcPyne

Expert 2060 points

Hello Marc,

sorry, no it doesn't. Or at least, I don't see how it can help me. The chapter describes the details of the system MMU, ok. But I don't understand how I can configure the MMU (which seems to be identical to the DEMMU, right?) in a way that I can access the PCIe memory address 0x20000000 from the DSP side.

There is "Table 5-1. L3 Master/Slave Connectivity" in SPRS680A. It seems to tell me, that the DSP has memory access only via the DEMMU (which I remember reading in one of the many other SPR*, too) and that EDMA has access to PCI Memory.

What I need is access to PCIe memory address 0x20000000 (and following), because that's where my peripherial sits that gives me data to process. No matter how this is done, but I really can't see what I have to do with the System MMU (or anything else, btw) to achieve this.

So I really need TIs help here...

Markus

0 MarcPyne over 14 years ago in reply to Markus Grunwald

TI__Mastermind 25055 points

Markus,

You are correct, the only masters that can access the PCIe Registers are the ARM Cortex-A8 and the EDMA; the DSP can access it via the DEMMU only. I will work to find you the information you need.

Regards,
Marc

0 Markus Grunwald over 14 years ago in reply to MarcPyne

Expert 2060 points

Thank you, it is very much appreciated!

0 Markus Grunwald over 14 years ago in reply to Markus Grunwald

Expert 2060 points

Hello,

do you have any news for me?

0 MarcPyne over 14 years ago in reply to Markus Grunwald

TI__Mastermind 25055 points

Sorry, not yet. I am still digging.

Regards,
Marc

0 Markus Grunwald over 14 years ago in reply to MarcPyne

Expert 2060 points

Hello,

I ended up with one-dword-edma-transfers. That's a lot of overhead for a simple memory access, but I need to go on somehow :s

Markus

0 MarcPyne over 14 years ago in reply to MarcPyne

TI__Mastermind 25055 points

Markus,

I confirmed that the PCIe on this device is accessible by ARM and EDMA only. It is not feasible to access from the DSP.

Regards,
Marc

0 Markus Grunwald over 14 years ago in reply to MarcPyne

Expert 2060 points

Hello Marc,

thanks for your investigations.

Markus

0 Jonathan Journo over 13 years ago in reply to Markus Grunwald

Intellectual 475 points

Hi Markus and Marc,

I have a similar problem.

I would like to access the GPMC memory connected to a FPGA directly from the DSP of the TI814x chip.

But the GPMC memory region seems to be accessible from DEMMU or EDMA only.

Marc,

Is the GPMC accessible from the DSP? if yes, how can I configure the DSP MMU to map it to the GPMC region? I do not found any useful guide or datasheet (except the TRM that is not really helpfull )

Markus,

I understood that you have already implement a EDMA access to the PCIe memory in the DSP side.

It will be very nice if you could share with me your EDMA programming solution at DSP side. I'll modified it for GPMC memory access.

Thanks for any advice.

0 MarcPyne over 13 years ago in reply to Jonathan Journo

TI__Mastermind 25055 points

Hello,

The DSP can access GPMC via the DEMMU only. The MMU needs to be configured to map the GPMC address range into a DSP addressable range via MMU.

Regards,
Marc

0 Jonathan Journo over 13 years ago in reply to MarcPyne

Intellectual 475 points

Hi Marc,

I successfully accessed the GPMC memory from the DSP via the EDMA without the DEMMU mapping.

Regarding DSP direct access via the DEMMU,

Is there any guide/information on how to configure the DEMMU in order to map the GPMC memory space or any other L3 peripheral.

Thanks,

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Accessing global memory ("devmem" on DSP)