From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cho KyongHo Subject: Re: [PATCH v11 10/27] iommu/exynos: use managed device helper functions Date: Thu, 20 Mar 2014 19:03:33 +0900 Message-ID: <20140320190333.9c3555b097e97d593faddbdd@samsung.com> References: <20140314140542.f4ded6c50dbd8a1d937bf354@samsung.com> <20140318200915.7dd833ce0fddbbd6ecd8dac9@samsung.com> <532862ED.8040809@samsung.com> <20140319175927.a3feadcacbffe80eca1d3421@samsung.com> <532988CA.4000008@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <532988CA.4000008-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Tomasz Figa Cc: Sachin Kamat , Linux ARM Kernel , Linux DeviceTree , Linux IOMMU , Linux Kernel , Linux Samsung SOC , Antonios Motakis , Grant Grundler , Joerg Roedel , Kukjin Kim , Prathyush , Rahul Sharma , Sylwester Nawrocki , Varun Sethi List-Id: linux-samsung-soc@vger.kernel.org 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 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 wrote: > >>>>>> This patch uses managed device helper functions in the probe(). > >>>>>> > >>>>>> Signed-off-by: Cho KyongHo > >>>>>> --- > >>>>> [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(). Regards, KyongHo -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html