On Thu, 20 Mar 2014 11:44:50 +0100, Tomasz Figa wrote: > On 20.03.2014 11:03, Cho KyongHo wrote: > > On Wed, 19 Mar 2014 13:08:42 +0100, Tomasz Figa wrote: > >> 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. > >> > > On early development step of a new SoC, clock related stuffs and > > some device drivers like display controller are usually developed in parallel. > > > > In that case, -ENOENT from clk_get() must not treated as an error. > > "[PATCH v11 20/17] iommu/exynos: allow having multiple System MMUs for a master H/W" > > patch distinguishes -ENOENT from other error values returned by devm_clk_get(). > > I still don't think upstream is right place for such development hacks > and such assumption will mask potential errors caused by clocks > unspecified in DT. > > If such thing is needed for development, an extra patch might be kept in > development tree, until clock driver is implemented or a dummy > fixed-rate clock might be specified in DT. > Ok. Now I understand. Error from clk_get() will be failure of probe in the next patch series. Thanks. KyongHo -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html