linux-kernel - Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux subsystem

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Date:	Thu, 15 Dec 2011 17:34:31 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	Dong Aisheng-B29396 <B29396@...escale.com>,
	Guo Shawn-R65073 <r65073@...escale.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux subsystem

On Thu, Dec 15, 2011 at 10:00:25PM +0800, Shawn Guo wrote:
> On Thu, Dec 15, 2011 at 02:23:36PM +0100, Sascha Hauer wrote:
> > On Thu, Dec 15, 2011 at 08:17:54PM +0800, Shawn Guo wrote:
> > > On Thu, Dec 15, 2011 at 12:54:28PM +0100, Sascha Hauer wrote:
> > > > On Thu, Dec 15, 2011 at 07:53:05PM +0800, Shawn Guo wrote:
> > > > > On Thu, Dec 15, 2011 at 07:28:18PM +0800, Dong Aisheng-B29396 wrote:
> > > > > > > -----Original Message-----
> > > > > > > 
> > > > > > My understanding is that pinmux_get will return an error if no proper pinmux
> > > > > > Found without dummy pinmux. That's a real error.
> > > > > > But with dummy pinmux, if no proper pinmux found, the pinctrl core may check
> > > > > > If dummy pinmux is supported, if supported, it will fakely success with returning
> > > > > > a dummy pinmux. Then real error is hiden.
> > > > > > This is due to for supporting one single image, the dummy pinmux may also be enabled
> > > > > > For platforms like mx6q with real pinmux.
> > > > > > 
> > > > > Got your point.  So your concern is about the fake success when dummy
> > > > > pinmux comes to play rather than 'fake error'.  I'm not concerned about
> > > > > that case much, since we will know the failure with a simple debug/info
> > > > > message in the pinmux core, saying 'I do not find any available pinmux,
> > > > > and I'm falling into the dummy pinmux'.  When you see this message
> > > > > imx6q, you know something goes wrong.
> > > > 
> > > > So i.MX3/5 people must know that it's safe to ignore this message
> > > > whereas i.MX6 people must know there's something wrong Adding messages
> > > > saying "there might or might not be something wrong" is not good.
> > > > People will frequently ask on the mailing list about these messages.
> > > > 
> > > Usually, people checking the serial output and asking question on list
> > > are developers not users.  It's not too hard for developers to figure
> > > out such message.  Or we can making it a debug message, and when some
> > > driver is not working, turn on debug option, you know where it goes
> > > wrong.
> > 
> > So we as developers have to figure out ourselves what can go wrong and
> > the users, well who cares about users?
> > 
> It's really the type of problem that can be discovered and fixed in
> the development phase, isn't it?
> 
> BTW, I did not mean to leave imx3 and imx5 there forever, but mean,
> with the dummy pinmux support, we do not have to strictly migrate imx3,
> imx5 and imx6 all at the same time.

I'm afraid your plans for i.MX3/5 clash with Freescale's i.MX7
release...

Sascha


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