RTL8188ETV chip, r8188eu module and power management

RTL8188ETV chip, r8188eu module and power management

[Anton Sviridenko]

Hello

we are using FN-8112MET PCB module having RTL8188ETV chip on it.
Device is running customized Linux version based on Linux 4.19 release.
Driver module "r8188eu" is not modified, taken from vanilla sources as
is.
Wi-Fi connection is used occasionally, and rest of the time it is
preferable to have minimal power consumption. 

Such situation is observed:

1) Linux kernel is started, driver module is not loaded
2) module "r8188eu" is loaded manually with parameters "rtw_power_mgnt=2
rtw_enusbss=1"
3) device starts consuming more current (+20mA)
3) after the module is unloaded, current consumption remains at the same
level

We still have to double-check this, but looks like driver module does
not leave the device in the same state on module unload.

Few questions:
1) Is "r8188eu" driver from the mainline kernel the best possible option
available for this chip?

2) Where can I look for some documentation about kernel module
parameters related to power management and their meanings? 
Source code is not very descriptive, and I was not able to google
anything better, looks like this chip specifications are not available in
public.

3) Is there some option to completely poweroff this chip using software
and then bring it back when needed?

Anton

Re: RTL8188ETV chip, r8188eu module and power management

[Larry Finger]

On 7/17/19 1:06 AM, Anton Sviridenko wrote:
> 
> Hello
> 
> we are using FN-8112MET PCB module having RTL8188ETV chip on it.
> Device is running customized Linux version based on Linux 4.19 release.
> Driver module "r8188eu" is not modified, taken from vanilla sources as
> is.
> Wi-Fi connection is used occasionally, and rest of the time it is
> preferable to have minimal power consumption.
> 
> Such situation is observed:
> 
> 1) Linux kernel is started, driver module is not loaded
> 2) module "r8188eu" is loaded manually with parameters "rtw_power_mgnt=2
> rtw_enusbss=1"
> 3) device starts consuming more current (+20mA)
> 3) after the module is unloaded, current consumption remains at the same
> level
> 
> We still have to double-check this, but looks like driver module does
> not leave the device in the same state on module unload.
> 
> Few questions:
> 1) Is "r8188eu" driver from the mainline kernel the best possible option
> available for this chip?
> 
> 2) Where can I look for some documentation about kernel module
> parameters related to power management and their meanings?
> Source code is not very descriptive, and I was not able to google
> anything better, looks like this chip specifications are not available in
> public.
> 
> 3) Is there some option to completely poweroff this chip using software
> and then bring it back when needed?

1. No. There is a newer driver for the RTL8188EU chips at 
http://github.com/lwfinger/rtl8188eu.git. The v5.2.2.4 branch has what I think 
is the best.

2. The source code is the only documentation available.

3. The page at 
https://unix.stackexchange.com/questions/165447/turning-off-power-to-usb-port-or-turn-off-power-to-entire-usb-subsystem 
has some info on disabling USB hubs that support per-port power switching.

Larry