From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933917AbaCSMIx (ORCPT ); Wed, 19 Mar 2014 08:08:53 -0400 Received: from mailout1.w1.samsung.com ([210.118.77.11]:20160 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758953AbaCSMIu (ORCPT ); Wed, 19 Mar 2014 08:08:50 -0400 X-AuditID: cbfec7f4-b7f796d000005a13-af-532988cf6aa6 Message-id: <532988CA.4000008@samsung.com> Date: Wed, 19 Mar 2014 13:08:42 +0100 From: Tomasz Figa Organization: Samsung R&D Institute Poland User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-version: 1.0 To: Sachin Kamat , Cho KyongHo Cc: 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 References: <20140314140542.f4ded6c50dbd8a1d937bf354@samsung.com> <20140318200915.7dd833ce0fddbbd6ecd8dac9@samsung.com> <532862ED.8040809@samsung.com> <20140319175927.a3feadcacbffe80eca1d3421@samsung.com> In-reply-to: Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmplkeLIzCtJLcpLzFFi42I5/e/4Nd3zHZrBBs8uClvcuXuO1WL+ESDx 6sgPJosF+60tOmdvYLfoXXCVzWLT42usFpd3zWGzmHF+H5PFhRUb2S3+9R5ktJiy6DCrxeE3 7awWJ//0MlrMvLWGxYHf48nBeUwesxsusnj8O9zP5HHn2h42j81L6j0m31jO6NG3ZRWjx+dN ch5Xjp5hCuCM4rJJSc3JLEst0rdL4MpYs6qDseAqT8XBla9YGxi/c3YxcnJICJhI9K89xgZh i0lcuLceyObiEBJYyijxcvFyFgjnM6PEvMU9zCBVvAJaEp9vPmYCsVkEVCXen7sJ1s0moCbx ueERmM0PVLOm6ToLiC0qECExd+JmNoheQYkfk++BxUUEAiRO/F7CDLKAWeA6i8Sz47vYQRLC QIkXJxugNj9gklg74yTQNg4OToFgiZVPLEBqmAWsJVZO2sYIYctLbF7zlnkCo+AsJDtmISmb haRsASPzKkbR1NLkguKk9FxDveLE3OLSvHS95PzcTYyQqPuyg3HxMatDjAIcjEo8vJKxGsFC rIllxZW5hxglOJiVRHgP1WsGC/GmJFZWpRblxxeV5qQWH2Jk4uCUamA0fJXot6TDzjdAwb7h //EnT1cLX5vy2GPjccWiqOkz4s+pdK9dnxEe3C20b9bPOcL6f/59tWfvm7/29Z5cnwenp2Rw L5+0P9XRIe6RqOrySXwnC+ynvJdtVpt/TazG84gsT5uCWLhgfKaTw3/ZfeV+0mHX+hdd7/qt fUBd49cOb+WQuunphdJKLMUZiYZazEXFiQCp2FmAmAIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Best regards, Tomasz