lkml.org 
[lkml]   [2016]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 0/8] power: add power sequence library
On Wed, Aug 24, 2016 at 04:53:35PM +0800, Peter Chen wrote:
> On Tue, Aug 23, 2016 at 04:02:48PM +0530, Vaibhav Hiremath wrote:
> >
> >
> > On Monday 15 August 2016 02:43 PM, Peter Chen wrote:
> > >Hi all,
> > >
> > >This is a follow-up for my last power sequence framework patch set [1].
> > >According to Rob Herring and Ulf Hansson's comments[2], I use a generic
> > >power sequence library for parsing the power sequence elements on DT,
> > >and implement generic power sequence on library. The host driver
> > >can allocate power sequence instance, and calls pwrseq APIs accordingly.
> > >
> > >In future, if there are special power sequence requirements, the special
> > >power sequence library can be created.
> > >
> > >This patch set is tested on i.mx6 sabresx evk using a dts change, I use
> > >two hot-plug devices to simulate this use case, the related binding
> > >change is updated at patch [1/6], The udoo board changes were tested
> > >using my last power sequence patch set.[3]
> > >
> > >Except for hard-wired MMC and USB devices, I find the USB ULPI PHY also
> > >need to power on itself before it can be found by ULPI bus.
> > >
> > >[1] http://www.spinics.net/lists/linux-usb/msg142755.html
> > >[2] http://www.spinics.net/lists/linux-usb/msg143106.html
> > >[3] http://www.spinics.net/lists/linux-usb/msg142815.html
> > (Please ignore my response on V2)
> >
> > Sorry being so late in the discussion...
> >
> > If I am not missing anything, then I am afraid to say that the
> > generic library
> > implementation in this patch series is not going to solve many of
> > the custom
> > requirement of power on, off, etc...
> > I know you mentioned about adding another library when we come
> > across such platforms, but should we not keep provision (or easy
> > hooks/path)
> > to enable that ?
> >
> > Let me bring in the use case I am dealing with,
> >
> >
> > Host
> > |
> > V
> > USB port
> > ------------------------------------------------------------
> > |
> > V
> > USB HUB device (May need custom on/off seq)
> > |
> > V
> > =============================
> > | |
> > V V
> > Device-1 Device-2
> > (Needs special power (Needs special power
> > on/off sequence. on/off sequence.
> > Also may need custom Also, may need custom
> > sequence for sequence for
> > suspend/resume) suspend/resume)
> >
> >
> > Note: Both Devices are connected to HUB via HSIC and may differ
> > in terms of functionality, features they support.
> >
> > In the above case, both Device-1 and Device-2, need separate
> > power on/off sequence. So generic library currently we have in this
> > patch series is not going to satisfy the need here.
> >
> > I looked at all 6 revisions of this patch-series, went through the
> > review comments, and looked at MMC power sequence code;
> > what I can say here is, we need something similar to
> > MMC power sequence here, where every device can have its own
> > power sequence (if needed).
> >
> > I know Rob is not in favor of creating platform device for
> > this, and I understand his comment.
> > If not platform device, but atleast we need mechanism to
> > connect each device back to its of_node and its respective
> > driver/library fns. For example, the Devices may support different
> > boot modes, and platform driver needs to make sure that
> > the right sequence is followed for booting.
> >
> > Peter, My apologies for taking you back again on this series.
> > I am OK, if you wish to address this in incremental addition,
> > but my point is, we know that the current generic way is not
> > enough for us, so I think we should try to fix it in initial phase only.
> >
>
> Rob, it seems generic power sequence can't cover all cases.
> Without information from DT, we can't know which power sequence
> for which device.
>

Vaibhav, do you agree that I create pwrseq library list using postcore_initcall
for each library, and choose pwrseq library according to compatible
string first, if there is no compatible string for this library, just
use generic pwrseq library.

--

Best Regards,
Peter Chen

\
 
 \ /
  Last update: 2016-09-17 09:58    [W:0.095 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site