[Letux-kernel] Fwd: mmc PM regression

Andreas Kemnade andreas at kemnade.info
Mon Feb 8 20:27:11 CET 2016


On Mon, 8 Feb 2016 11:18:23 +0100
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
> > Am 07.02.2016 um 22:22 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > Hi Nikolaus,
> > 
> > On Sun, 7 Feb 2016 10:53:38 +0100
> > "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> > 
> >> 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.
> >> 
> > BT seems to have quite good power saving.
> > I have booted 4.5rc2 with init=/bin/bash
> > loading modules, ifconfig wlan0 up (no connection), 
> > hciattach, hciconfig hci0 up
> > and running l2ping gives 90mA total consumption, around 80mA without l2ping.
> 
> Well, Bluetooth in total has not a big consumption. I think <50mA.
> 
> But 10mA is a lot...
> 
I would guess that 10mA without l2ping running is like 40% wifi, 40% bt and
the rest soc/glue.

> > 
> >>> Are there any other reason besides saving a few mA (which is of course
> >>> important)?
> >> 
> >> Very important, and more important than everything else...
> >> 
> > That does not answer my question. 
> 
> Maybe I can't answer it because I have not written that code...
> 
I think we have misunderstood each other. 

I did understand your "Vaux4 *must* be turned off if bt+wifi is not used"
like "you cannot expect that the system runs stable under that condition"

I do not see a reason for that so I ask you as a board designer for reasons.

And you probably have talked about your expression what a good kernel should
do: perfect powersaving.

Regards,
Andreas
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