AM6548: Access Memory Region for R5

sarfaraz shaikh

Part Number: AM6548

Hi TI,

In the am6548 dts we have seperate memory region for R5 e.g.

mcu_r5fss0_core1_dma_memory_region: r5f-dma-memory@a1000000 {
compatible = "shared-dma-pool";
reg = <0 0xa1000000 0 0x100000>;
no-map;
};

1. How can I access this region from A53 side (Running TI SDK Linux)

2. I need to access the data in R5 memory region without using devmem. Is there any application to access that region

Please share your thoughts on this.

Thanks,

Sarfaraz

over 3 years ago

0 Hemant Hariyani over 3 years ago

TI__Expert 8385 points

Hello,

Why not devmem? You can also write an application and use mmap with /dev/mem

fd = open("/dev/mem", O_RDWR|O_SYNC);

mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, phys_addr)

Regards

Hemant

0 Suman Anna over 3 years ago in reply to Hemant Hariyani

TI__Guru** 112475 points

Hi Sarfaraz,

1. This region is reserved for primarily for the firmware's text, local data and heaps. This region is owned and mapped into the respective remoteproc driver, but is not exposed to other kernel entities or userspace.

2. You can always use IPC to exchange small data. If you are talking about separate shared memory region, then you have to define a dma-buf-heap, and access it through the corresponding DMA BUF API.

/dev/mem is to be used only for debug purposes, but cannot be used on actual production software due to the security holes it poses.

regards

Suman

0 sarfaraz shaikh over 3 years ago in reply to Suman Anna

Expert 1536 points

Yes. the main concern for dev/mem is cybersecurity. IPC calls like read / write are blocking calls, is there a different approach to asynchronously accessing the shared region from a53 side ?

regarding the dma-buf-heap is there any reference example for remoteproc ?

Thanks

0 Suman Anna over 3 years ago in reply to sarfaraz shaikh

TI__Guru** 112475 points

Hi Sarfaraj,

I am not sure I understand your asynchronous point. If you are using a shared memory, you would have to use a notification to let the other side know that there is new data. Ofcourse, you can always use polling if you do not want to use messaging.

The Vision Apps in RTOS SDK has a utility library for dealing with dma-buf-heaps.

You can see the following FAQ (NOTE: This applies to 7.0 SDK and is not updated for latest SDKs): https://e2e.ti.com/support/processors-group/processors/f/processors-forum/909695/faq-tda4vm-makefile-based-project-which-shows-a72-c7x-r5f-setup-along-with-ipc-and-buffer-passing-between-linux-rtos

Please see the Vision Apps Utils Mem API. You can look up the source code in <RTOS SDK>/vision_apps/utils/mem/src/app_mem_linux_dma_heap.c if you want to write your own helper functions. This relies on a vision_apps_shared-memories reserved-memory node defined in the Linux dts.

regards

Suman

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AM6548: Access Memory Region for R5