Why does mailbox_client_flash_open() fail after mailbox_client_open() in SDM Bootloader for the Nios® V Processor targeting Intel Agliex® 7 FPGA?

Due to a problem that the Intel Agliex® 7 FPGA Secure Device Manager (SDM) is busy with FPGA initialization, Nios® V HAL function mailbox_client_flash_open() may fail to open flash after mailbox_client_open() when running SDM Bootloader.

To work around this problem in Intel Agliex® 7 FPGA Secure Device Manager, add a delayed attempt after function mailbox_client_flash_open() to open flash in the main function in <Project Location>\top_project\sw\mailbox_bootloader\app\mailbox_bootloader.c. 

The max attempts shown below are 1000, and each attempt is delayed by 10 milliseconds.

attribute_((noreturn)) int main(int argc, char **argv){

intel_mailbox_client* mbox_client = mailbox_client_open(MBOX_NAME);

int record_address_ptr = PAYLOAD_OFFSET;

// Obtain exclusive flash access 

int attempt = 0;

int MAX_ATTEMPTS = 1000;

while((mailbox_client_flash_open(mbox_client)!=0) &&(++attempt < MAX_ATTEMPTS)){ usleep(10000);

if (attempt == MAX_ATTEMPTS) error();

......