[Sound-open-firmware] SOF: Where is the purpose of host_msg ?

[Daniel Baluta]

Hi Pierre/Liam,

In src/include/sof/ipc.h there is:

struct ipc {
     uint32_t host_msg;»     »       /* current message from host */
//
}

This keeps the message received from IA core. Anyhow, DSP core
doesn't seem to use it at all.

Except maybe for some logging:

src/drivers/intel/baytrail/ipc.c:                       _ipc->host_msg = msg;
src/drivers/intel/baytrail/ipc.c:       trace_ipc("ipc: msg rx ->
0x%x", ipc->host_msg);
src/drivers/intel/cavs/ipc.c:                   _ipc->host_msg = msg;
src/drivers/intel/cavs/ipc.c:   trace_ipc("ipc: msg rx -> 0x%x", ipc->host_msg);
src/drivers/intel/cavs/sue-ipc.c:       trace_ipc("ipc: msg rx ->
0x%x", ipc->host_msg);
src/drivers/intel/haswell/ipc.c:                        _ipc->host_msg = msg;
src/drivers/intel/haswell/ipc.c:        trace_ipc("ipc: msg rx ->
0x%x", ipc->host_msg);
src/include/sof/ipc.h:  uint32_t host_msg;              /* current
message from host */

I am asking this because initially I thought the communication between
IA core and DSP involves:

- sending cmd using shim layer
- sending actual data using mailbox.

But it seems that all the information is exchanged via the mailbox memory. So,
going back to my question will host_msg be used in the future?

If not, I think it is best to remove it because it is confusing.

The same happens when DSP tries to send something to IA.

For example it writes msg->header. But this is never used on the other side.

ipc_platform_send_msg

»       /* now interrupt host to tell it we have message sent */
»       shim_write(SHIM_IPCDL, msg->header);
»       shim_write(SHIM_IPCDH, SHIM_IPCDH_BUSY);

Also, would be easier for me on the ARM side to only send info via mailbox and
notification via what you call shim layer.

thanks,
Daniel.