From: Peter Chen <hzpeterchen@gmail.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <k.kozlowski@samsung.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
linux-mmc <linux-mmc@vger.kernel.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
linux-usb@vger.kernel.org, Sebastian Reichel <sre@kernel.org>,
Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>,
David Woodhouse <dwmw2@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mark Brown <broonie@kernel.org>,
hverkuil@xs4all.nl, tjakobi@math.uni-bielefeld.de,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [RFC v2 00/13] usb/mmc/power: Fix USB/LAN when TFTP booting
Date: Tue, 31 May 2016 08:58:08 +0800 [thread overview]
Message-ID: <20160531005808.GA7913@shlinux2> (raw)
In-Reply-To: <20160528033613.GA3291@shlinux2>
On Sat, May 28, 2016 at 11:36:13AM +0800, Peter Chen wrote:
> On Tue, May 10, 2016 at 01:02:08PM +0200, Ulf Hansson wrote:
> > + Arnd
> >
> > [...]
> >
> > >> >> Solution
> > >> >> ========
> > >> >> This is very similar to the MMC pwrseq behavior so the idea is to:
> > >> >> 1. Move MMC pwrseq drivers to generic place,
> > >> >
> > >> > You can do that, but I'm going to NAK any use of pwrseq bindings outside
> > >> > of MMC. I think it is the wrong way to do things. The DT should describe
> > >>
> > >> Huh, I didn't know that was your view of the mmc pwrseq bindings. Why
> > >> didn't you NAK them before?
> > >
> > > Unfortunately, either I missed it or it was a time I couldn't spend much
> > > time on reviews.
> >
> > Okay, I guess it's common issue among maintainers. The problem with DT
> > is that it gets really hard to be fixed up later. :-)
> >
> > >
> > >> > the devices. If they happen to be "simple" then the core can walk the
> > >> > tree and do any setup. For example, look for "reset-gpios" and toggle
> > >> > that GPIO. There is no need for a special node.
> > >> >
> > >> >> 2. Extend the pwrseq-simple with regulator toggling,
> > >> >> 3. Add support to USB hub and port core for pwrseq,
> > >> >
> > >> > We discussed this for USB already[1] and is why we defined how to add
> > >> > USB child devices. The idea is not to add pwrseq to that.
> > >>
> > >> I am not familiar with the USB discussion.
> > >>
> > >> Still, let me give you some more background to the mmc pwrseq. The
> > >> idea from the mmc pwrseq bindings comes from the power-domain DT
> > >> bindings, as I thought these things were a bit related.
> > >> In both cases they are not directly a property of the device, but more
> > >> describing a HW dependency to allow the device to work.
> > >
> > > I could see this as a board level power domain. However the difference
> > > is we are not generally exposing internal SOC details the same way as
> > > board level components. Perhaps we could extend power domains to board
> > > level, but that is not what was done here.
> > >
> > >> One could probably use a child node instead of a phandle, but that
> > >> wasn't chosen back then. Of course you are the DT expert, but could
> > >> you perhaps tell me why a child node is better for cases like this?
> > >
> > > If there is a control path hierarchy, then we try to model that in DT
> > > with child nodes. In cases of SDIO and USB, there is a clear hierarchy.
> > > Ignoring the discovery ordering problem, we already have defined ways to
> > > describe GPIO connections, regulators, etc. to devices. Describing those
> > > things separately from the device to solve a particular issue that is
> > > really a kernel limitation is what I don't like.
> >
> > Okay, I see.
> >
> > To move forward in trying to make mmc pwrseq a generic pwrseq, could
> > we perhaps allow both cases?
> >
> > In the mmc case, there are already deployed bindings so we need to
> > cope with these by using the phandle option, but for USB etc we could
> > force the child node option.
> > As long as we agree that we keep using a compatible string for the
> > child node as well, both options should be able to co-exist and we
> > should probably be able to managed them both from a common pwrseq
> > driver framework.
> >
> > Although, I do remember from an older conversations around some of
> > mine submission for the mmc pwrseq code, that some people (maybe
> > Arnd?) wasn't keen on adding a new framework for this. Perhaps that
> > has changed?
> >
>
> All, how we move on for this?
>
> 1. Using a generic driver to manage both mmc and USB (and further
> subsystem), USB and further subsystem do not use pwrseq node in dts.
> 2. USB creates the similar driver under drivers/usb for its own use.
>
> Which one do you prefer, thanks.
>
Hi Krzysztof Kozlowski,
I think option 1 may be better according to Rob and Ulf's comment.
Would you like going on your patch set? You can work on generic pwrseq
driver, I will do USB stuffs based on generic pwrseq driver?
--
Best Regards,
Peter Chen
next prev parent reply other threads:[~2016-05-31 0:58 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 12:34 [RFC v2 00/13] usb/mmc/power: Fix USB/LAN when TFTP booting Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 01/13] usb: misc: usb3503: Clean up on driver unbind Krzysztof Kozlowski
2016-05-05 18:32 ` Javier Martinez Canillas
2016-05-06 6:13 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 02/13] power/mmc: Move pwrseq drivers to power/pwrseq Krzysztof Kozlowski
2016-05-05 18:44 ` Javier Martinez Canillas
2016-05-06 6:15 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 03/13] MAINTAINERS: Retain Ulf Hansson as the same maintainer of pwrseq Krzysztof Kozlowski
2016-05-05 18:46 ` Javier Martinez Canillas
2016-05-05 12:34 ` [RFC v2 06/13] power: pwrseq: Generalize mmc_pwrseq operations by removing mmc prefix Krzysztof Kozlowski
[not found] ` <1462451666-17945-7-git-send-email-k.kozlowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-05 19:14 ` Javier Martinez Canillas
2016-05-05 12:34 ` [RFC v2 07/13] power: pwrseq: simple: Add support for toggling regulator Krzysztof Kozlowski
2016-05-05 19:31 ` Javier Martinez Canillas
2016-05-06 6:24 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 08/13] usb: hub: Handle deferred probe Krzysztof Kozlowski
2016-05-05 19:33 ` Javier Martinez Canillas
2016-05-05 12:34 ` [RFC v2 09/13] power: pwrseq: Add support for USB hubs with external power Krzysztof Kozlowski
[not found] ` <1462451666-17945-10-git-send-email-k.kozlowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-05 19:52 ` Javier Martinez Canillas
2016-05-06 6:26 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 10/13] usb: hub: Power sequence the ports on activation Krzysztof Kozlowski
[not found] ` <1462451666-17945-11-git-send-email-k.kozlowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-05 14:09 ` Alan Stern
2016-05-05 17:37 ` Krzysztof Kozlowski
2016-05-05 19:56 ` Javier Martinez Canillas
[not found] ` <1462451666-17945-1-git-send-email-k.kozlowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-05 12:34 ` [RFC v2 04/13] power: pwrseq: Enable COMPILE_TEST for drivers Krzysztof Kozlowski
[not found] ` <1462451666-17945-5-git-send-email-k.kozlowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-05 18:57 ` Javier Martinez Canillas
2016-05-05 12:34 ` [RFC v2 05/13] power: pwrseq: Remove mmc prefix from mmc_pwrseq Krzysztof Kozlowski
2016-05-05 19:09 ` Javier Martinez Canillas
2016-05-06 6:20 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 11/13] usb: port: Parse pwrseq phandle from Device Tree Krzysztof Kozlowski
2016-05-05 20:10 ` Javier Martinez Canillas
2016-05-06 6:27 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 12/13] ARM: dts: exynos: Switch the buck8 to GPIO mode on Odroid U3 Krzysztof Kozlowski
2016-05-05 20:11 ` Javier Martinez Canillas
2016-05-05 22:42 ` [RFC v2 00/13] usb/mmc/power: Fix USB/LAN when TFTP booting Rob Herring
2016-05-06 5:44 ` Peter Chen
2016-05-06 6:12 ` Krzysztof Kozlowski
[not found] ` <572C35C8.9080709-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
2016-05-06 7:15 ` Peter Chen
2016-05-06 6:10 ` Krzysztof Kozlowski
2016-05-06 13:01 ` Rob Herring
2016-05-09 7:46 ` Ulf Hansson
2016-05-09 18:18 ` Rob Herring
2016-05-10 11:02 ` Ulf Hansson
[not found] ` <CAPDyKFq2=mqujFjvJSYxg2nVmK=OrBKLtFfb-ErNJO3Zr_LMVw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-05-28 3:36 ` Peter Chen
2016-05-31 0:58 ` Peter Chen [this message]
2016-05-31 11:54 ` Krzysztof Kozlowski
2016-05-05 12:34 ` [RFC v2 13/13] ARM: dts: exynos: Fix LAN and HUB after bootloader initialization on Odroid U3 Krzysztof Kozlowski
2016-05-05 20:16 ` Javier Martinez Canillas
2016-05-06 6:28 ` Krzysztof Kozlowski
2016-12-13 12:20 ` [RFC v2 00/13] usb/mmc/power: Fix USB/LAN when TFTP booting Hans Verkuil
2016-12-13 12:34 ` Hans Verkuil
2016-12-13 13:53 ` Krzysztof Kozlowski
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