RE: Unable to access EGU registers on NRF9160

Nick Ewalt — Wed, 07 Jun 2023 17:34:33 GMT

Ah, excellent. We are still using SPM from NCS v1.7.1. I'll backport 010d7ea0 to switch the other EGUs to NS. It's reassuring to know that TF-M does the same.

RE: Unable to access EGU registers on NRF9160

Håkon Alseth — Wed, 07 Jun 2023 08:02:43 GMT

Hi,

Which NCS version are you using? Since you mention SPM directly, I assume you're using NCS v2.1 or older.

Here's the code that sets the permission(s) for the EGU instances:

https://github.com/nrfconnect/sdk-nrf/blob/v2.1.4/subsys/spm/spm.c#L368-L385

These are by default set to non-secure in ncs v2.1.x:

*** Booting Zephyr OS build v3.1.99-ncs1-3  ***
Flash regions           Domain          Permissions
00 01 0x00000 0x10000   Secure          rwxl
02 31 0x10000 0x100000  Non-Secure      rwxl

Non-secure callable region 0 placed in flash region 1 with size 32.

SRAM region             Domain          Permissions
00 03 0x00000 0x08000   Secure          rwxl
04 31 0x08000 0x40000   Non-Secure      rwxl

Peripheral              Domain          Status
00 NRF_P0               Non-Secure      OK
01 NRF_CLOCK            Non-Secure      OK
02 NRF_RTC0             Non-Secure      OK
03 NRF_RTC1             Non-Secure      OK
04 NRF_NVMC             Non-Secure      OK
05 NRF_UARTE1           Non-Secure      OK
06 NRF_UARTE2           Non-Secure      OK
07 NRF_TWIM2            Non-Secure      OK
08 NRF_SPIM3            Non-Secure      OK
09 NRF_TIMER0           Non-Secure      OK
10 NRF_TIMER1           Non-Secure      OK
11 NRF_TIMER2           Non-Secure      OK
12 NRF_SAADC            Non-Secure      OK
13 NRF_PWM0             Non-Secure      OK
14 NRF_PWM1             Non-Secure      OK
15 NRF_PWM2             Non-Secure      OK
16 NRF_PWM3             Non-Secure      OK
17 NRF_WDT              Non-Secure      OK
18 NRF_IPC              Non-Secure      OK
19 NRF_VMC              Non-Secure      OK
20 NRF_FPU              Non-Secure      OK
21 NRF_EGU0             Non-Secure      OK
22 NRF_EGU1             Non-Secure      OK
23 NRF_EGU2             Non-Secure      OK
24 NRF_EGU3             Non-Secure      OK
25 NRF_EGU4             Non-Secure      OK
26 NRF_EGU5             Non-Secure      OK
27 NRF_DPPIC            Non-Secure      OK
28 NRF_REGULATORS       Non-Secure      OK
29 NRF_PDM              Non-Secure      OK
30 NRF_I2S              Non-Secure      OK
31 NRF_GPIOTE1          Non-Secure      OK

Are you using TF-M? If yes, the zephyr/samples/subsys/shell/devmem_load sample is able read the address successfully in ncs v2.3.0:

*** Booting Zephyr OS build v3.2.99-ncs2 ***
uart:~$ devmem 4001b300 32
Using data width 32
Read value 0x0

Kind regards,

Håkon

RE: Unable to access EGU registers on NRF9160

Nick Ewalt — Tue, 06 Jun 2023 23:42:37 GMT

It turns out that I actually can access EGU1 and EGU2, but none of the others. The underlying cause was that SPM only configures EGU1 and EGU2 to be non-secure in the SPU, leaving the rest as secure by default. It seems like the modem lib uses those two instances for application and tracing IRQs respectively.

It's unclear why SPM doesn't configure the others to be accessible to the NS application, does anyone know the reason? I assume it will be fine if I modify SPM to do so.