S32KのトピックRe: problem managed ipcf s32k3

problem managed ipcf s32k3

michelet1 — Mon, 07 Oct 2024 15:56:52 GMT

Good evening,

i am analyzing ipcf for s32k324 in the managed case as shown in the attached image.

I instantiated a buffer of 10 values on core0 and tried to send it to core1. By varying the size parameter i did not notice any changes, in the sense that with any size value set other than zero you send the entire buffer to core1.

I wanted to ask what is the meaning of the size parameter in the shm_tx function because seems to don’t have any control on parameter “size”.

The current SW we are developing is based on RTD 3.0.0,S32K3xx_AMMCLIB_v1.1.34, IPCF S32K3xx 4.0.0

thanks in advance for any help and information.

Re: problem managed ipcf s32k3

danielmartynek — Thu, 10 Oct 2024 13:19:52 GMT

Hi @michelet1,

It is a zero copy mechanism.

When we send a message, we basically provide the other core with a pointer to the buffer and the size of it.

The size is then an argument in the callback.

When CM7_0 sends data it performs the following:

acquires a buffer
populates the buffer
sends a notification to CM7_1

Once CM7_1 receives the callback, it does the following:

calculates the pointer address
reads and use the data (no need to copy as the buffer is locked until it is released by the user)
releases the buffer (in order to be reused)

BR, Daniel

Re: problem managed ipcf s32k3

michelet1 — Thu, 10 Oct 2024 16:07:57 GMT

hi,

thanks for your reply.

i just have a doubt.

if core0 acquire a buffer of 10 items and send it but specifies a size=2,

on core1 should receive only 2 items and not all 10 items, am i right?

why do i find the entire buffer on core1 for any size value i specify?

thanks again for the availability

Michele

Re: problem managed ipcf s32k3

danielmartynek — Fri, 11 Oct 2024 07:23:06 GMT

Hi Michele,

Because it does not send anything.

The other core is notified that there are data in a buffer of a certain size defined by ipc_shm_tx(size).

BR, Daniel

Re: problem managed ipcf s32k3

michelet1 — Fri, 11 Oct 2024 12:09:38 GMT

Hi,

thanks for the answer.

i'm still not clear about the meaning of the size parameter? shouldn't it indicate how much buffer data i want to send from one core to another?

let's make a practical example:

if i have a buff[10] and specify size=2 as the ipc_shm_tx() parameter on core0, on core1 the notify should go off and only read buf[0] and buf[1], is this reasoning correct?

thanks again for your availability

Michele

Re: problem managed ipcf s32k3

danielmartynek — Fri, 11 Oct 2024 13:46:34 GMT

Yes, core_1 is notified to read just buf[0] and buf[1].

Regards,

Daniel