[Letux-kernel] Fwd: mmc PM regression

H. Nikolaus Schaller hns at goldelico.com
Sun Feb 7 10:53:38 CET 2016


Hi Andreas,

> Am 07.02.2016 um 10:06 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> Hi Nikolaus,
> 
> On Fri, 5 Feb 2016 19:30:27 +0100
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>>> &mmc2 {
>>>       vmmc-supply = <&vaux4>;
>>>       bus-width = <4>;
>>>       ti,non-removable;
>>>       cap-power-off-card;     /* remove! */ <----
>>> };
>>> What about the "remove!" here? What are the plans/ideas/problems here?  
>> 
>> I don't know.
>> 
> If I understand that correctly, then that is about what to do with vaux4.
> Thats why I asked my question below.
> 
>>> Was it once enabled and caused problems?
>>> 277acf4b545327104c9b779eec7c440285d11a39
>>> looks like that.  
>> 
>> That is heritage from Neil nobody else was able to understand so far...
>> 
>>> 
>>> Is the idea to never switch off vaux4? At least everything
>>> regarding sdio suspend/remove/resume should be tested in both ways  
>> 
>> No, vaux4 must be turned off if we neither need WLAN nor BT.
>> 
> It should. But *must* it be turned off?

Yes. It is also shared with the Bluetooth side... So if you keep the WLAN
running we will also have ~50mA for bluetooth.

> Are there any other reason besides saving a few mA (which is of course
> important)?

Very important, and more important than everything else...

> If no then it is better to test any sdio-related patches
> with and without removal so nothing breaks on other boards where
> the 'card" does not have its own regulator.

Well, all WLAN cards I know have some enable/regulator.
For example the wl183x we have for the Pyra or GTA04A5.

In our case we have it twice: vaux4 for "enable" and the tca6507 GPIO
for "reset".

The difference between reset and enable is more philosophical... But there
may be a timing difference. If both are present, the reset should be asserted
for a while after powering on the device.

BR,
Nikolaus



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