Re: [PATCH v2] i2c: sh_mobile: implement atomic transfers

[Wolfram Sang <wsa@the-dreams.de>]

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On Thu, Jun 25, 2020 at 05:16:58PM +0200, Wolfram Sang wrote:
> Hi Geert,
> 
> I spend some more thoughts on this.
> 
> > > > In general, pm_runtime_get_sync() is not safe to call from atomic
> > > > context.
> > > > For Renesas SoCs, I think both the power and clock domains are safe, as
> > > > the respective drivers don't sleep.  The PM core might, though.
> > >
> > > Still, that sounds to me like we should protect these calls as in V1?
> 
> I still think we should guard these calls just because it is not safe to
> call them from atomic contexts.
> 
> > And talk to the i2c controller while it is disabled?
> 
> Is there maybe some "always-on" property which we could add to the
> respective IIC clock?

Ping to this question...

> 
> > That does seem to work on R-Car Gen2 (similar to SMP bringup accessing
> > registers of a disabled WDT?), though.
> 
> Yes. Uli's patch will not cause a regression because we are already
> calling i2c_transfer very late. And we do call the runtime_pm functions
> currently. So, it will improve the situation there.
> 
> > Needs testing on R-Mobile A1....
> 
> That's armadillo, right? I don't have that, sadly.
> 
> Thanks,
> 
>    Wolfram
> 



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