RE: [PATCH rtw-next] wifi: rtw88: 8821c: disable deep LPS on PCIe devices

[Ping-Ke Shih]

Paolo Lazzaroni <eexto@xxxxxxx> wrote:
> Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx> wrote:
> > Disabling LPS_PG doesn't mean disabling LCLK, I think.
> 
> Ping-Ke Shih <pkshih@xxxxxxxxxxx> wrote:
> > Indeed. bLPS_PG_En should be LPS_DEEP_MODE_PG which 8821c's
> > .lps_deep_mode_supported doesn't declare this.
> 
> Ah, got it. Sorry, my mistake.
> 
> > First line of block comment should be empty.
> 
> Will fix this style in the next revision.
> 
> > I'll consult internally to see if we disable deep PS entirely
> > for this chip.
> >
> > My question is that are you 100% sure this can resolve the problem
> > you encountered?
> 
> To be transparent: on my HP 15-da0xxx (subsystem 103c:831a), I was originally
> using module parameters (disable_lps_deep=y and disable_aspm=y) while debugging
> the antenna issue.
> 
> After your question, I tested my laptop with upstream default settings
> (disable_lps_deep=n, disable_aspm=n, power_save=on). Using ftrace on
> rtw_power_mode_change over a 1-hour test, the card entered and left 32kHz
> LCLK deep sleep hundreds of times without any freeze or firmware error. So
> on my specific HP laptop, deep LPS actually works fine.

That is the case in our side. I don't see the error. But laptop is different
from yours though. 

> 
> I proposed this patch and added the reporters in Cc (Gabriel, Rahul, Mihail,
> Ata) because multiple platforms (HP, ASUS TUF, Lenovo, Dell) keep hitting
> hard freezes with 8821CE PCIe, and adding DMI quirks one by one is hard
> to maintain.

I knew DMI quirks is little hard to maintain, so an alternative way is
to use module parameters (disable_lps_deep=y and disable_aspm=y).

By our measurement, the power consumption without deep PS increases about
16mA (3.3V) for RTL8821CE. The value is not very large, but if platforms
can enter the mode, it is still good.

> 
> So I can't be 100% sure for their hardware without their confirmation.
> We hope someone in Cc can join the discussion and test this patch to see
> if it definitively fixes their freeze, which would also help anyone who might
> encounter this problem in the future.
> 
> Thank you for consulting internally at Realtek. I will hold off on v2
> until your internal feedback.

The affected power consumption is listed above. 

Ping-Ke