From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756886AbaCTKDi (ORCPT ); Thu, 20 Mar 2014 06:03:38 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:21618 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756126AbaCTKDf (ORCPT ); Thu, 20 Mar 2014 06:03:35 -0400 X-AuditID: cbfee68e-b7f566d000002344-ea-532abcf541c2 Date: Thu, 20 Mar 2014 19:03:33 +0900 From: Cho KyongHo 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 Subject: Re: [PATCH v11 10/27] iommu/exynos: use managed device helper functions Message-id: <20140320190333.9c3555b097e97d593faddbdd@samsung.com> In-reply-to: <532988CA.4000008@samsung.com> References: <20140314140542.f4ded6c50dbd8a1d937bf354@samsung.com> <20140318200915.7dd833ce0fddbbd6ecd8dac9@samsung.com> <532862ED.8040809@samsung.com> <20140319175927.a3feadcacbffe80eca1d3421@samsung.com> <532988CA.4000008@samsung.com> X-Mailer: Sylpheed 3.3.0 (GTK+ 2.10.14; i686-pc-mingw32) MIME-version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrJIsWRmVeSWpSXmKPExsVy+t8zY92ve7SCDbYftrG4c/ccq8X8I0Di 1ZEfTBYL9ltbdM7ewG7Ru+Aqm8Wmx9dYLS7vmsNmMeP8PiaLCys2sltMWXSY1eLwm3ZWi5N/ ehkt1s94zWIx89YaFgd+jycH5zF5zG64yOLx73A/k8eda3vYPDYvqfeYfGM5o0ffllWMHp83 yXlcOXqGKYAzissmJTUnsyy1SN8ugSuja9l21oJXAhWTdn5la2Ds4e1i5OSQEDCRODJnBiuE LSZx4d56ti5GLg4hgWWMEpd2r2SEKep7NYUFIrGIUeLuz4+MEM5kJombL6eAtbMIqEq8/t0C ZrMJaEmsnnscrFtEQEXi8qnpYA3MAo2sEr9nnGEHSQgLBEi8ONnAAmLzCjhKbN70hA3E5hTQ lng+ZQ2YLSTQyCzRtjgX4gwLiQtNHewQ9YISPybfA+tlBlq2eVsTK4QtL7F5zVtmiPqFHBL3 HulAHCcg8W3yIaB6DqC4rMSmA1AlkhIHV9xgmcAoNgvJ1FlIps5CMnUBI/MqRtHUguSC4qT0 IiO94sTc4tK8dL3k/NxNjJBo79vBePOA9SHGZKCVE5mlRJPzgckiryTe0NjMyMLUxNTYyNzS jDRhJXHeRQ+TgoQE0hNLUrNTUwtSi+KLSnNSiw8xMnFwSjUwavxUPvSoeEpbA9eR6R6OvzWX vXntU87h5bs04WRa6d0pCZ+azy0J/P3bzqu8+tV/SSWtrUusXBW0z+8Ru2C2ZHfBfF4PK63z v91Nk8/Plfevzvuok/N7w6M7n/bcvzMt4cPJLz+dotofreXbLh+7p81A2OV5UG3f08Nvjt3O yp5qzOnNk3JttRJLcUaioRZzUXEiAIvPIj4MAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrOKsWRmVeSWpSXmKPExsVy+t9jAd2ve7SCDXZtMrO4c/ccq8X8I0Di 1ZEfTBYL9ltbdM7ewG7Ru+Aqm8Wmx9dYLS7vmsNmMeP8PiaLCys2sltMWXSY1eLwm3ZWi5N/ ehkt1s94zWIx89YaFgd+jycH5zF5zG64yOLx73A/k8eda3vYPDYvqfeYfGM5o0ffllWMHp83 yXlcOXqGKYAzqoHRJiM1MSW1SCE1Lzk/JTMv3VbJOzjeOd7UzMBQ19DSwlxJIS8xN9VWycUn QNctMwfoAyWFssScUqBQQGJxsZK+HaYJoSFuuhYwjRG6viFBcD1GBmggYR1jRtey7awFrwQq Ju38ytbA2MPbxcjJISFgItH3agoLhC0mceHeerYuRi4OIYFFjBJ3f35khHAmM0ncfDmFFaSK RUBV4vXvFjCbTUBLYvXc44wgtoiAisTlU9PBGpgFGlklfs84ww6SEBYIkHhxsgFsBa+Ao8Tm TU/YQGxOAW2J51PWgNlCAo3MEm2LcyHOsJC40NTBDlEvKPFj8j2wXmagZZu3NbFC2PISm9e8 ZZ7AKDALSdksJGWzkJQtYGRexSiaWpBcUJyUnmukV5yYW1yal66XnJ+7iRGcTJ5J72Bc1WBx iFGAg1GJh3fFHs1gIdbEsuLK3EOMEhzMSiK81u5awUK8KYmVValF+fFFpTmpxYcYk4HBMZFZ SjQ5H5jo8kriDY1NzIwsjcwsjEzMzUkTVhLnPdhqHSgkkJ5YkpqdmlqQWgSzhYmDU6qBMeHb vL+zdF784jt1vu7cvQKJjQwGir1H/SdH+t3tvPXdYVHZiv+h+kEVkU8X1EVpxB6JuJAX8kJW NCb85dMtO0tzP77NEfhf6aibfvfN+/ZO1bNCvP8uOKqqLp7m8URxnu2qOylvGuZp+i+3Ld0b +aFTomuibszXg/OUyrZs7jy0d7eSMa9EuBJLcUaioRZzUXEiAKJZn05qAwAA DLP-Filter: Pass X-MTR: 20000000000000000@CPGS X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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