Power draw increases after setting CONFIG_PM_DEVICE_RUNTIME=y

[simonhwm]

I was using an SPI serial nor flash device with NCS 2.8.0. I tried to get the flash into deep power down mode, but it doesn't seem to work well with NCS 2.8.0. So I upgraded to 3.1.0

In itself this gives the same current consumption within the margin of error.

I now set CONFIG_PM_DEVICE_RUNTIME=y and in my flash device initialisation I call pm_device_runtime_enable() on the flash device and the DPD commands appear on the SPI bus as expected.

However, with CONFIG_PM_DEVICE_RUNTIME and DPD enabled, the overall current draw is now slightly higher than before, and if I don't call pm_device_runtime_enable for the flash device then it is higher again. I was expecting this to reduce overall consumption, not increase it.

2.8.0, no CONFIG_PM_DEVICE_RUNTIME = 51uA

3.1.0, no CONFIG_PM_DEVICE_RUNTIME = 52uA

3.1.0, CONFIG_PM_DEVICE_RUNTIME=y, no DPD = 63uA

3.1.0, CONFIG_PM_DEVICE_RUNTIME=y, DPD enabled = 55uA

How has enabling CONFIG_PM_DEVICE_RUNTIME made it worse?

Simon

[Menon]

Hello,

Can you check if this is causing leakage and resulting in higher current? Leave SCK/MOSI/MISO floating during sleep.

Kind Regards,

Abhijith

[simonhwm]

That is the same regardless of whether CONFIG_PM_DEVICE_RUNTIME=y is set.

The reason the output pins are set high is that the serial flash device is still powered on and floating those lines makes the flash chip consume more power.

Simon