[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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