mt7915: enabling DPD does not adjust tx power

[hyunhi2]

Hi, I'm trying to use dynamic tx power adjustment with my E8450 router.

I saw the comment "firmware dynamically adjusts PD threshold so skip manual control",
so I expected the router to dynamically adjust tx power if I call mt7915_mcu_enable_obss_spr with SPR_ENABLE_DPD and SPR_ENABLE_SD in mcu.c to enable DPD.
I tested with my two E8450 routers, but tx power remained nearly constant in the presence of about -70 dBm co-channel interference.

Is there a way to make the E8450 dynamically adjust tx power?
If not, does BPI-R4 eqipped with mt7988A support this feature?