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

[Pankaj Dubey]

Hi Boris,

On Wednesday, September 03, 2014 Boris BREZILLON wrote,
> To: Arnd Bergmann
> Cc: Pankaj Dubey; kgene.kim@xxxxxxxxxxx; linux@xxxxxxxxxxxxxxxx; Alexander
> Shiyan; naushad@xxxxxxxxxxx; Tomasz Figa; linux-kernel@xxxxxxxxxxxxxxx;
> joshi@xxxxxxxxxxx; linux-samsung-soc@xxxxxxxxxxxxxxx;
thomas.ab@xxxxxxxxxxx;
> tomasz.figa@xxxxxxxxx; vikas.sajjan@xxxxxxxxxxx; chow.kim@xxxxxxxxxxx;
> lee.jones@xxxxxxxxxx; Michal Simek; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
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@xxxxxxxx> 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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