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

[Ping-Ke Shih]

Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx> wrote:
> On 19/09/2026 02:28, Paolo Lazzaroni wrote:
> > On RTL8821CE PCIe adapters, entering 32kHz low-power clock deep sleep
> > (LPS_DEEP_MODE_LCLK) causes recurrent PCIe completion timeouts,
> > "firmware failed to leave lps state", "failed to send h2c command",
> > and hard system freezes when transitioning out of low power states with
> > PCIe ASPM enabled.
> >
> > To work around this, a DMI quirk list (rtw_pci_quirks[]) was introduced
> > and has grown across HP, ASUS, Dell, and Lenovo machines. However, DMI
> > matching is unsustainable: minor sub-model variances (such as ASUS
> > FA506II vs FA506IH) or unlisted models (such as ASUS VivoBook X515JA,
> > Bmax Y14, or modern Alder Lake-N mini PCs) leave users experiencing bus
> > lockups or firmware drops unless they manually turn off power saving via
> > iw.
> >
> > Examination of official OEM Windows driver INF files for RTL8821CE
> > (HP and ASUS netrtwlane.inf) reveals that vendor drivers explicitly
> > disable deep power saving (WoWLANPSMode = 0, bLPS_PG_En = 0) and enable
> 
> Disabling LPS_PG doesn't mean disabling LCLK, I think.

Indeed. bLPS_PG_En should be LPS_DEEP_MODE_PG which 8821c's
.lps_deep_mode_supported doesn't declare this. 

> 
> > firmware PCIe recovery, while keeping standard PCIe ASPM enabled.
> > Furthermore, other chips in rtw88 (RTL8723DE, RTL8812AE, RTL8821AE)
> > already set lps_deep_mode_supported = 0 by default.
> 
> What those other chips are doing is not relevant. RTL8812AE and
> RTL8821AE are not officially supported in rtw88. (Not yet?)
> lps_deep_mode_supported is zero in rtw8812a.c and rtw8821a.c because
> rtw88_usb doesn't implement deep PS and I didn't research which
> modes they could support if deep PS was implemented for USB.
> 
> >
> > Conservatively disable LPS_DEEP_MODE_LCLK specifically for RTL8821C on
> > PCIe interfaces in rtw_update_lps_deep_mode(). Standard 802.11 LPS
> > power saving and PCIe ASPM remain functional, preventing system lockups
> > and firmware failures without affecting SDIO or USB variants.
> >
> > Signed-off-by: Paolo Lazzaroni <eexto@xxxxxxx>
> > ---
> >  drivers/net/wireless/realtek/rtw88/main.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw88/main.c b/drivers/net/wireless/realtek/rtw88/main.c
> > index 0f23498b5..5bd854223 100644
> > --- a/drivers/net/wireless/realtek/rtw88/main.c
> > +++ b/drivers/net/wireless/realtek/rtw88/main.c
> > @@ -1360,6 +1360,14 @@ static enum rtw_lps_deep_mode rtw_update_lps_deep_mode(struct rtw_dev *rtwdev,
> >           !fw->feature)
> >               return LPS_DEEP_MODE_NONE;
> >
> > +     /* RTL8821CE PCIe devices fail to wake up from 32kHz LCLK deep sleep

First line of block comment should be empty.

> > +      * in time for PCIe completion deadlines, leading to PCIe bus freeze
> 
> Completion timeout is already disabled for this chip.
> 
> > +      * and communication timeouts.
> > +      */
> > +     if (rtw_hci_type(rtwdev) == RTW_HCI_TYPE_PCIE &&
> > +         chip->id == RTW_CHIP_TYPE_8821C)
> > +             return LPS_DEEP_MODE_NONE;
> > +
> >       if ((chip->lps_deep_mode_supported & BIT(LPS_DEEP_MODE_PG)) &&
> >           rtw_fw_feature_check(fw, FW_FEATURE_PG))
> >               return LPS_DEEP_MODE_PG;
> 
> However, I'm not saying it's necessarily wrong to disable deep PS for
> this chip completely. I'm just objecting to your LLM's conclusions.

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? 

Ping-Ke