linux-kernel - RE: [PATCH v2] mfd: syscon: Decouple syscon interface from platform devices

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Date:	Thu, 04 Sep 2014 10:15:27 +0530
From:	Pankaj Dubey <pankaj.dubey@...sung.com>
To:	'Boris BREZILLON' <boris.brezillon@...e-electrons.com>,
	'Arnd Bergmann' <arnd@...db.de>
Cc:	kgene.kim@...sung.com, linux@....linux.org.uk,
	'Alexander Shiyan' <shc_work@...l.ru>, naushad@...sung.com,
	'Tomasz Figa' <t.figa@...sung.com>,
	linux-kernel@...r.kernel.org, joshi@...sung.com,
	linux-samsung-soc@...r.kernel.org, thomas.ab@...sung.com,
	tomasz.figa@...il.com, vikas.sajjan@...sung.com,
	chow.kim@...sung.com, lee.jones@...aro.org,
	'Michal Simek' <michal.simek@...inx.com>,
	linux-arm-kernel@...ts.infradead.org,
	'Mark Brown' <broonie@...nel.org>
Subject: RE: [PATCH v2] mfd: syscon: Decouple syscon interface from platform
 devices

Hi Boris,

On Wednesday, September 03, 2014 Boris BREZILLON wrote,
> To: Arnd Bergmann
> Cc: Pankaj Dubey; kgene.kim@...sung.com; linux@....linux.org.uk; Alexander
> Shiyan; naushad@...sung.com; Tomasz Figa; linux-kernel@...r.kernel.org;
> joshi@...sung.com; linux-samsung-soc@...r.kernel.org;
thomas.ab@...sung.com;
> tomasz.figa@...il.com; vikas.sajjan@...sung.com; chow.kim@...sung.com;
> lee.jones@...aro.org; Michal Simek; linux-arm-kernel@...ts.infradead.org;
Mark
> Brown
> Subject: Re: [PATCH v2] mfd: syscon: Decouple syscon interface from
platform
> devices
> 
> On Wed, 03 Sep 2014 15:49:04 +0200
> Arnd Bergmann <arnd@...db.de> wrote:
> 
> > On Wednesday 03 September 2014 15:16:11 Boris BREZILLON wrote:
> > > I checked that part, and it appears most of the code is already
> > > there (see usage of regmap_attach_dev function here [1]).
> > >
> > > The only problem I see is that errors are still printed with
> > > dev_err, which, AFAIK, will trigger a kernel panic if dev is NULL.
> >
> > Actually not:
> >
> > static int __dev_printk(const char *level, const struct device *dev,
> >                         struct va_format *vaf) {
> >         if (!dev)
> >                 return printk("%s(NULL device *): %pV", level, vaf);
> >
> >         return dev_printk_emit(level[1] - '0', dev,
> >                                "%s %s: %pV",
> >                                dev_driver_string(dev), dev_name(dev),
> > vaf); }
> >
> 
> My bad then (I don't know where I looked at to think NULL dev was not
gracefully
> handled :-)). Thanks for pointing this out.
> Given that, I think it should work fine even with a NULL dev.
> I'll give it a try on at91 ;-).
> 

We have tested this patch, on Exynos board and found working well.
In our use case DT based drivers such as USB Phy, SATA Phy, Watchdog are
calling 
syscon_regmap_lookup_by APIs to get regmap handle to Exynos PMU and it
worked 
well for these drivers. 

It would be great if after testing you share result here or give a
Tested-By.

Thanks,
Pankaj Dubey 
> Best Regards,
> 
> Boris
> 
> --
> Boris Brezillon, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

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