Re: [PATCH] arm_mpam: Warn when firmware leaves PARTIDs disabled

[Ping Li]

Hi Ben,

Thanks for sharing the direction. I asked our hardware team why they
implemented HAS_ENDIS: the motivation is power. Enabling PARTIDs that
are never used does not affect performance, but costs leakage in the
registers and combinational logic behind them - with e.g. 32 PARTIDs
implemented and only a handful ever used, the unused portion is pure
waste. Their expectation was that software would enable only the
PARTIDs it needs at initialization time.

For a general-purpose driver that cannot predict how many PARTIDs
userspace will actually use, that is not something we can do. So what
I plan to do is either enable all the PARTIDs from the driver, or ask
the hardware team to drop the HAS_ENDIS feature.

I am happy to drop this warning patch in favour of your driver-side
enabling patch.

Thanks,
Ping