From: Arnd Bergmann <arnd@arndb.de>
To: Felipe Balbi <balbi@kernel.org>
Cc: Peter Chen <hzpeterchen@gmail.com>, Leo Li <pku.leo@gmail.com>,
Grygorii Strashko <grygorii.strashko@ti.com>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
Sekhar Nori <nsekhar@ti.com>, lkml <linux-kernel@vger.kernel.org>,
Stuart Yoder <stuart.yoder@nxp.com>,
Scott Wood <oss@buserror.net>,
David Fisher <david.fisher1@synopsys.com>,
"Thang Q. Nguyen" <tqnguyen@apm.com>,
Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev
Date: Thu, 08 Sep 2016 14:46:51 +0200 [thread overview]
Message-ID: <7818609.ZAbFcr85D0@wuerfel> (raw)
In-Reply-To: <87r38uhalt.fsf@linux.intel.com>
On Thursday, September 8, 2016 2:52:46 PM CEST Felipe Balbi wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
> >> If we make dwc3.ko a library which glue calls directly then all these
> >> problems are solved but we break all current DTs and fall into the trap
> >> of having another MUSB.
> >
> > I don't see how we'd break the current DTs, I'm fairly sure we could turn dwc3
>
> well, at a minimum dwc3-{pci,exynos,st,omap,of-simple}.c would have to
> look at possible children for their own quirks and properties.
>
> > into a library without changing the DT representation. However the parts
> > that I think would change are
> >
> > - The sysfs representation for dwc3-pci, as we would no longer have
> > a parent-child relationship there.
>
> that's a no-brainer, I think
>
> > - The power management handling might need a rework, since you currently
> > rely on the hierarchy between dwc3-pci, dwc3 and xhci for turning
> > power on and off
>
> simple enough to do as well.
>
> > - turning dwc3 into a library probably implies also turning xhci into
> > a library, in part for consistency.
>
> yeah, I considered that too. We could still do it in parts, though.
>
> > - if we don't do the whole usb_bus->sysdev thing, we need to not just
> > do this for dwc3 but also chipidea and maybe a couple of others.
>
> MUSB comes to mind
Right.
> > There should not be any show-stoppers here, but it's a lot of work.
>
> I think the biggest work will making sure people don't abuse functions
> just because they're now part of a single binary. Having them as
> separate modules helped a lot reducing the maintenance overhead. There
> was only one occasion where someone sent a glue layer which iterated
> over its children to find struct dwc3 * from child's drvdata.
This is where it get a bit philosophical ;-)
I understand that you like the strict separation that the current model
provides, and I agree that can be an advantage.
Changing the abstraction model to a set of library modules the way that
other drivers (e.g. ehci, sdhci, or libata) work to me means changing
this separation model into a different model and once we do that I would
not consider it a mistake for the platform specific driver to take
advantage of that. You still get a bit of separation since the drivers
would be in separate modules that can only access exported symbols,
and the library can still hide its data structures (to some degree).
I still think that turning xhci (and dwc3) into a library would be
an overall win, but if we solve the problems of DMA settings and
usb_device DT properties without it, I'd prefer not to fight over
that with you again ;-)
> >> If we try to pass DMA bits from parent to child, then we have the fact
> >> that DT ends up, in practice, always having a parent device.
> >
> > I don't understand what you mean here, but I agree that the various ways
>
> well, we can't simply use what I pointed out a few emails back:
>
> if (dwc->dev->parent)
> dwc->sysdev = dwc->dev->parent
> else
> dwc->sysdev = dwc->dev
Ok, I see.
> > we discussed for copying the DMA flags from one 'struct device' to another
> > all turned out to be flawed in at least one way.
> >
> > Do you see any problems with the patch I posted other than the ugliness
> > of the dwc3 and xhci drivers finding out which pointer to use for
> > usb_bus->sysdev? If we can solve this, we shouldn't need any new
> > of_dma_configure/acpi_dma_configure calls and we won't have to
> > turn the drivers into a library, so maybe let's try to come up with
> > better ideas for that sub-problem.
>
> No big problems with that, no. Just the ifdef looking for a PCI bus in
> the parent. How about passing a flag via device_properties? I don't
> wanna change dwc3 core's device name with a platform_device_id because
> there probably already are scripts relying on the names to enable
> pm_runtime for example.
Sounds ok to me. Grygorii's solution might a be a bit more elegant,
but also a bit more error-prone:
If we get a platform that mistakenly sets the dma_mask pointer of
the child device, or a platform that does not set the dma_mask
pointer of the parent, things break.
Arnd
next prev parent reply other threads:[~2016-09-08 12:47 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-25 19:21 [PATCH] usb: dwc3: host: inherit dma configuration from parent dev Grygorii Strashko
2016-04-26 6:17 ` Felipe Balbi
2016-04-26 8:14 ` Grygorii Strashko
2016-04-27 5:41 ` Felipe Balbi
2016-04-27 11:55 ` Grygorii Strashko
2016-04-27 13:59 ` Catalin Marinas
2016-04-27 14:11 ` Arnd Bergmann
2016-04-27 15:50 ` Catalin Marinas
2016-04-27 16:04 ` Arnd Bergmann
2016-04-27 16:53 ` Felipe Balbi
2016-04-27 17:42 ` Arnd Bergmann
2016-04-27 17:59 ` Alan Stern
2016-04-27 18:08 ` Arnd Bergmann
2016-04-27 20:05 ` Felipe Balbi
2016-04-27 21:05 ` Arnd Bergmann
2016-04-28 6:37 ` Felipe Balbi
2016-04-28 14:16 ` Russell King - ARM Linux
2016-04-28 14:23 ` Arnd Bergmann
2016-04-28 14:27 ` Felipe Balbi
2016-09-01 22:14 ` Leo Li
2016-09-02 10:43 ` Arnd Bergmann
2016-09-02 10:47 ` Russell King - ARM Linux
2016-09-02 11:08 ` Felipe Balbi
2016-09-02 14:11 ` Felipe Balbi
2016-09-02 14:21 ` Alan Stern
2016-09-02 15:51 ` Arnd Bergmann
2016-09-07 7:17 ` Roger Quadros
2016-09-07 8:29 ` Arnd Bergmann
2016-09-07 13:04 ` Roger Quadros
2016-09-07 14:38 ` Arnd Bergmann
2016-09-02 16:23 ` Grygorii Strashko
2016-09-02 10:53 ` Felipe Balbi
2016-09-02 11:55 ` Robin Murphy
2016-09-02 12:56 ` Felipe Balbi
2016-09-02 13:10 ` Arnd Bergmann
2016-09-02 22:16 ` Leo Li
2016-09-05 15:39 ` Arnd Bergmann
2016-09-06 6:35 ` Peter Chen
2016-09-06 6:40 ` Felipe Balbi
2016-09-06 10:46 ` Arnd Bergmann
2016-09-06 10:50 ` Felipe Balbi
2016-09-06 13:27 ` Arnd Bergmann
2016-09-07 6:51 ` Felipe Balbi
2016-09-07 7:44 ` Peter Chen
2016-09-07 8:52 ` Arnd Bergmann
2016-09-07 9:29 ` Peter Chen
2016-09-07 9:35 ` Russell King - ARM Linux
2016-09-07 10:18 ` Felipe Balbi
2016-09-06 10:38 ` Arnd Bergmann
2016-09-07 6:33 ` Peter Chen
2016-09-07 8:48 ` Arnd Bergmann
2016-09-07 9:55 ` Peter Chen
2016-09-07 10:33 ` Robin Murphy
2016-09-07 10:47 ` Felipe Balbi
2016-09-14 16:31 ` Lorenzo Pieralisi
2016-09-14 21:50 ` Arnd Bergmann
2016-09-07 10:24 ` Felipe Balbi
2016-09-07 15:24 ` Arnd Bergmann
2016-09-07 16:08 ` Alan Stern
2016-09-07 19:45 ` Arnd Bergmann
2016-09-08 1:15 ` Peter Chen
2016-09-08 8:02 ` Arnd Bergmann
2016-09-08 8:03 ` Felipe Balbi
2016-09-08 8:26 ` Arnd Bergmann
2016-09-08 8:29 ` Felipe Balbi
2016-09-08 8:45 ` Arnd Bergmann
2016-09-08 9:43 ` Felipe Balbi
2016-09-08 10:17 ` Arnd Bergmann
2016-09-08 11:00 ` Felipe Balbi
2016-09-08 11:11 ` Arnd Bergmann
2016-09-08 11:20 ` Felipe Balbi
2016-09-08 11:39 ` Arnd Bergmann
2016-09-08 11:52 ` Felipe Balbi
2016-09-08 12:46 ` Arnd Bergmann [this message]
2016-09-08 12:02 ` Grygorii Strashko
2016-09-08 12:14 ` Arnd Bergmann
2016-09-08 12:28 ` Peter Chen
2016-09-08 12:52 ` Arnd Bergmann
2016-09-09 1:37 ` Peter Chen
2016-09-08 12:59 ` Grygorii Strashko
2016-09-09 1:52 ` Peter Chen
2016-09-21 11:06 ` Sriram Dash
2016-09-21 11:31 ` Arnd Bergmann
2016-09-21 11:43 ` Sriram Dash
2016-09-21 12:48 ` Arnd Bergmann
2016-09-22 5:02 ` Sriram Dash
2016-10-07 22:46 ` Leo Li
2016-09-21 17:14 ` [PATCH] usb: xhci: Fix the patch inherit dma configuration from kbuild test robot
2016-04-27 20:57 ` [PATCH] usb: dwc3: host: inherit dma configuration from parent dev Felipe Balbi
2016-04-27 14:14 ` Grygorii Strashko
2016-05-05 17:07 ` Brian Norris
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7818609.ZAbFcr85D0@wuerfel \
--to=arnd@arndb.de \
--cc=balbi@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=david.fisher1@synopsys.com \
--cc=gregkh@linuxfoundation.org \
--cc=grygorii.strashko@ti.com \
--cc=hzpeterchen@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=linux@arm.linux.org.uk \
--cc=nsekhar@ti.com \
--cc=oss@buserror.net \
--cc=pku.leo@gmail.com \
--cc=stern@rowland.harvard.edu \
--cc=stuart.yoder@nxp.com \
--cc=tqnguyen@apm.com \
--cc=yoshihiro.shimoda.uh@renesas.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).