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

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Date:	Thu, 4 Sep 2014 08:03:59 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Pankaj Dubey <pankaj.dubey@...sung.com>
Cc:	'Arnd Bergmann' <arnd@...db.de>, 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 Pankaj

On Thu, 04 Sep 2014 10:15:27 +0530
Pankaj Dubey <pankaj.dubey@...sung.com> wrote:

> 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. 

Great!

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

Yep, that's the idea.
Let me some time to rework the PMC drivers (drivers/clk/at91/pmc.c) and
test it, and I'll add my Tested-by ;-).

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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