RE: [PATCH rtw-next v1 06/13] wifi: rtw89: Disable some power saving for USB

[Ping-Ke Shih <pkshih@realtek.com>]

Bitterblue Smith <rtl8821cerfe2@gmail.com> wrote:
> On 13/05/2025 06:27, Ping-Ke Shih wrote:
> > Bitterblue Smith <rtl8821cerfe2@gmail.com> wrote:
> >> Disable rtw89_ps_power_mode_change() and rtw89_mac_send_rpwm() for
> >> USB because they are called in atomic context and accessing hardware
> >> registers results in "scheduling while atomic" errors.
> >
> > I feel rtw89_ps_power_mode_change() should be not in atomic context.
> > Please check this.
> >
> 
> I think you're right, only rtw89_mac_send_rpwm() is called in atomic
> context. rtw89_ps_power_mode_change() is disabled for other reasons:

The rtw89_ps_power_mode_change() is to enter deep power save mode, which
can save more power save but need to leave the mode before you are going
to do IO/TX/RX. That means if you totally disable it, code flow would
be simpler, but power consumption would be higher. Since this is the
first patches to enable USB, I suggest you can disable it totally for
now, and add it later. 

> 
> 1) It calls rtw89_mac_power_mode_change(), which prints errors when
> rtw89_mac_send_rpwm() is disabled.
> 
> 2) With RTL8852CU it calls rtw89_ps_power_mode_change_with_hci()
> which calls napi_schedule(). That results in dereferencing a null
> pointer.

I see. Your implementation doesn't use NAPI for USB devices. 

The rtw89_ps_power_mode_change_with_hci() is to switch IO address for
PCI devices in deep power save mode, and USB devices don't need this.
I think we can run this only if HCI is PCI.