Re: [PATCH v11 10/27] iommu/exynos: use managed device helper functions

[Tomasz Figa]

On 19.03.2014 10:01, Sachin Kamat wrote:
> On 19 March 2014 14:29, Cho KyongHo <pullip.cho@xxxxxxxxxxx> wrote:
> > On Tue, 18 Mar 2014 16:14:53 +0100, Tomasz Figa wrote:
> > > On 18.03.2014 12:09, Cho KyongHo wrote:
> > > > On Fri, 14 Mar 2014 20:52:43 +0530, Sachin Kamat wrote:
> > > > > Hi KyongHo,
> > > > >
> > > > > On 14 March 2014 10:35, Cho KyongHo <pullip.cho@xxxxxxxxxxx> wrote:
> > > > > > This patch uses managed device helper functions in the probe().
> > > > > >
> > > > > > Signed-off-by: Cho KyongHo <pullip.cho@xxxxxxxxxxx>
> > > > > > ---
> > > > > [snip]
> > > > >
> > > > > > +       data->clk = devm_clk_get(dev, "sysmmu");
> > > > > > +       if (IS_ERR(data->clk)) {
> > > > > > +               dev_info(dev, "No gate clock found!\n");
> > > > > > +               data->clk = NULL;
> > > > > > +       }
> > > > >
> > > > > Why aren't you returning from here upon error?
> > > >
> > > > It is for the case of a System MMU which does not need clock gating.
> > >
> > > Are there really such cases?
> >
> > Yes.
> > Especially in the case of initial stage of new SoC development.
> >
> > I have experianced some software workaround for H/W restriction
> > needs prevention of clock gating for some devices.
>
> So aren't these basically some exceptions/hacks rather than the usual way
> of functioning of the device?

This actually raises a good question, whether we really need to support 
such early development SoC versions in mainline.

Another thing is that if you need to assure that a clock is ungated, you 
must acquire it and prepare_enable explicitly, so I don't think this 
kind of handling is correct.

Best regards,
Tomasz
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