Re: [BUG] wifi: rtw88: Hard system freeze on RTL8821CE when power_save is enabled (LPS/ASPM conflict)

[LB F <goainwo@gmail.com>]

Ping-Ke Shih <pkshih@realtek.com> wrote:
> I'd adopt your suggestion (dynamic LPS_DEEP_MODE_NONE) if the test
> is positive.

Hi Ping-Ke,

Following your suggestion, I performed an additional experiment to
validate the dynamic LPS_DEEP_MODE_NONE idea. Please treat this
purely as a field test report -- I am not a kernel developer, and the
implementation below is certainly not upstream-quality. I am sharing
it only in the hope that it helps you design a proper solution.

What I did:

I extended your DMI quirk in pci.c with an additional capability flag
for LPS Deep mode. The only file touched was pci.c (your patch) --
main.c was left completely unmodified.

The changes to your patch are as follows:

  /* 1. Extended the capabilities enum */
  enum rtw88_quirk_dis_pci_caps {
          QUIRK_DIS_PCI_CAP_ASPM,
          QUIRK_DIS_PCI_CAP_LPS_DEEP,  /* test addition */
  };

  /* 2. Extended disable_pci_caps() callback */
  static int disable_pci_caps(const struct dmi_system_id *dmi)
  {
          uintptr_t dis_caps = (uintptr_t)dmi->driver_data;

          if (dis_caps & BIT(QUIRK_DIS_PCI_CAP_ASPM))
                  rtw_pci_disable_aspm = true;

          if (dis_caps & BIT(QUIRK_DIS_PCI_CAP_LPS_DEEP))
                  rtw_disable_lps_deep_mode = true;

          return 1;
  }

  /* 3. Both flags set for the HP P3S95EA#ACB entry */
  .driver_data = (void *)(BIT(QUIRK_DIS_PCI_CAP_ASPM) |
                          BIT(QUIRK_DIS_PCI_CAP_LPS_DEEP)),

I am aware that setting rtw_disable_lps_deep_mode from pci.c is
architecturally impure -- it is a global flag that would affect all
rtw88 devices in a hypothetical multi-adapter system. A proper
per-device solution (e.g. a flag inside struct rtw_dev set during
probe) would be cleaner. I simply used the existing global as the
most straightforward way to validate the concept.

Verification:

Confirmed no rtw88-related entries exist in /etc/modprobe.d/,
/lib/modprobe.d/, or /run/modprobe.d/, ruling out any external
parameter injection.

After loading the patched modules, the following was confirmed via
sysfs:

  /sys/module/rtw88_core/parameters/disable_lps_deep_mode = Y
  /sys/module/rtw88_pci/parameters/disable_aspm = Y

This confirms the DMI quirk is the sole source of both values.

Results (10-minute idle observation, battery power, wifi.powersave=3):

  With your ASPM patch alone (LPS Deep still active):
    - periodic "failed to send h2c command" bursts observed
    - occasional WiFi throughput drops and Bluetooth audio stuttering

  With ASPM patch + LPS Deep disabled via the quirk:
    - h2c=0, lps=0 across the entire observation window
    - WiFi throughput stable, Bluetooth audio uninterrupted

The result confirms that disabling LPS Deep Mode in addition to ASPM
completely eliminates the remaining firmware timeout loop on this
platform.

I hope this experiment is useful as a data point. Please feel free to
discard the implementation and design a proper solution -- I am ready
to test any updated patch you send.

Best regards,
Oleksandr Havrylov