lockup with nrf_serial_flush while wait_for_flash_ready in nrf_nvmc_page_erase

[eleven-x_devteam]

Hi,

In my project, there is a lockup issue like the title. (SDK 15.3.0_59ac345)

When I try to erase flash, some data (uart command for the device)comes up through the uart and the device try to prints log for it and it hangs.

When I add some the other command not related to flash stuff, the issue disappears and it seems because it changes the timing.

But I don't understand why this problem happens and is there any way to avoid this?

I don't think I can share the code but I captured the call stack of the issue.

Thank you.

[eleven-x_devteam]

I am using the code below for prining debug log

ret = nrf_serial_write(&serial_uart, buffer, strlen(buffer), NULL, NRF_SERIAL_MAX_TIMEOUT);
APP_ERROR_CHECK(ret);

(void)nrf_serial_flush(&serial_uart, NRF_SERIAL_MAX_TIMEOUT);

and it looks like the device is hanging at the do while code in nrf_serial_flush()

do
{
empty = nrf_queue_is_empty(p_serial->p_ctx->p_config->p_queues->p_txq)
&& !nrf_drv_uart_tx_in_progress(&p_serial->instance);
if (empty)
{
break;
}

sleep_handler(p_serial);
} while (!tout_ctx.expired);

[eleven-x_devteam]

This is not lockup but serial driver error and the uart doesn't work anymore.

So it looks like this solution (https://devzone.nordicsemi.com/f/nordic-q-a/39902/how-to-recover-from-nrf_serial-driver-errors) can fix this issue but still, I don't know why the serial driver error happened.

Can flash stuff cause it?

[haakonsh]

It's probably an interrupt that was not serviced in time. From Erasing a page in flash: 

"When erase is enabled, the flash memory can be erased page by page using the ERASEPAGE.

After erasing a flash page, all bits in the page are set to 1. The time it takes to erase a page is specified by t_ERASEPAGE. The CPU is halted if the CPU executes code from the flash while the NVMC is writing to the flash.

See Partial erase of a page in flash for information on dividing the page erase time into shorter chunks."

Also, from Electrical specification: 

tERASEPAGE

Time to erase one page

851

ms

[eleven-x_devteam]

Thank you for your support.

Ok then maybe I can try to use the partial erase stuff.

But My device is using softdevice for BLE and nvmc is restricted when softdevice is enabled.

Is it possible to use the partial erase in this case and any example code?

[haakonsh]

yes, but you'll have to use the TimeSlot API to get a TimeSlot where have complete control of the system for the given time-period. 

Or you can sync your flash operations with your uart operations.

I'm going on vacation for a week, but I'll assign your case to another Tech Supporter.

BR,

Håkon HoldhusI