Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751690AbdF1M3e (ORCPT ); Wed, 28 Jun 2017 08:29:34 -0400 Received: from mx07-00178001.pphosted.com ([62.209.51.94]:36046 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751509AbdF1M33 (ORCPT ); Wed, 28 Jun 2017 08:29:29 -0400 From: Hugues FRUCHET To: "H. Nikolaus Schaller" , Sylwester Nawrocki CC: Guennadi Liakhovetski , Rob Herring , Mark Rutland , Maxime Coquelin , Alexandre TORGUE , Mauro Carvalho Chehab , Hans Verkuil , devicetree , linux-arm-kernel , LKML , "linux-media@vger.kernel.org" , Benjamin Gaignard , Yannick FERTRE , Discussions about the Letux Kernel Subject: Re: [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module Thread-Topic: [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module Thread-Index: AQHS7AsrZmrpjOmQsEi0MtyfQJVBP6I6ANiAgAAZpYA= Date: Wed, 28 Jun 2017 12:28:31 +0000 Message-ID: <2d916065-fd81-6f52-5d32-a46331e0c5ed@st.com> References: <1498143942-12682-1-git-send-email-hugues.fruchet@st.com> <1498143942-12682-2-git-send-email-hugues.fruchet@st.com> <64e3005d-31df-71f2-762b-2c1b1152fc2d@st.com> <5cd25a47-f3be-8c40-3940-29f26a245076@kernel.org> <39501C78-7B81-4803-94C1-25DFA06EA526@goldelico.com> <6F68CD33-70E6-47C1-9E89-5E2AA776879F@goldelico.com> <5bcc7ec0-4ae5-3703-3cee-ed644eef710a@samsung.com> <9D51AC4C-6CB7-46A5-B363-2AD6DA6C497F@goldelico.com> In-Reply-To: <9D51AC4C-6CB7-46A5-B363-2AD6DA6C497F@goldelico.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.75.127.48] Content-Type: text/plain; charset="utf-8" Content-ID: <29AEB76E89C20F42BE1AF53C84C02888@st.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-28_07:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id v5SCThAO008998 Content-Length: 4410 Lines: 100 On 06/28/2017 01:24 PM, H. Nikolaus Schaller wrote: > >> Am 28.06.2017 um 12:50 schrieb Sylwester Nawrocki : >> >> On 06/28/2017 11:12 AM, H. Nikolaus Schaller wrote: >>>> Am 28.06.2017 um 00:57 schrieb Sylwester Nawrocki : >>>> On 06/27/2017 07:48 AM, H. Nikolaus Schaller wrote: >>>>>> Am 26.06.2017 um 22:04 schrieb Sylwester Nawrocki : >>>>>> On 06/26/2017 12:35 PM, Hugues FRUCHET wrote: >>>>>>>> What I am missing to support the GTA04 camera is the control of the optional "vana-supply". >>>>>>>> So the driver does not power up the camera module when needed and therefore probing fails. >>>>>>>> >>>>>>>> - vana-supply: a regulator to power up the camera module. >>>>>>>> >>>>>>>> Driver code is not complex to add: >>>>>> >>>>>>> Yes, I saw it in your code, but as I don't have any programmable power >>>>>>> supply on my setup, I have not pushed this commit. >>>>>> >>>>>> Since you are about to add voltage supplies to the DT binding I'd suggest >>>>>> to include all three voltage supplies of the sensor chip. Looking at the OV9650 >>>>>> and the OV9655 datasheet there are following names used for the voltage supply >>>>>> pins: >>>>>> >>>>>> AVDD - Analog power supply, >>>>>> DVDD - Power supply for digital core logic, >>>>>> DOVDD - Digital power supply for I/O. >>>>> >>>>> The latter two are usually not independently switchable from the SoC power >>>>> the module is connected to. >>>>> >>>>> And sometimes DVDD and DOVDD are connected together. >>>>> >>>>> So the driver can't make much use of knowing or requesting them because the >>>>> 1.8V supply is always active, even during suspend. >>>>> >>>>>> >>>>>> I doubt the sensor can work without any of these voltage supplies, thus >>>>>> regulator_get_optional() should not be used. I would just use the regulator >>>>>> bulk API to handle all three power supplies. >>>>> >>>>> The digital part works with AVDD turned off. So the LDO supplying AVDD should >>>>> be switchable to save power (&vaux3 on the GTA04 device).> >>>>> But not all designs can switch it off. Hence the idea to define it as an >>>>> /optional/ regulator. If it is not defined by DT, the driver simply assumes >>>>> it is always powered on. >>>> >>>> I didn't say we can't define regulator supply properties as optional in the DT >>>> binding. If we define them as such and any of these *-supply properties is >>>> missing in DT with regulator_get() the regulator core will use dummy regulator >>>> for that particular voltage supply. While with regulator_get_optional() >>>> -ENODEV is returned when the regulator cannot be found. >>> >>> Ah, ok. I see. >>> >>> I had thought that it is the right thing to do like devm_gpiod_get_optional(). >>> >>> That one it is described as: >>> >>> "* This is equivalent to gpiod_get(), except that when no GPIO was assigned to >>> * the requested function it will return NULL. This is convenient for drivers >>> * that need to handle optional GPIOs." >>> >>> Seems to be inconsistent definition of what "optional" means. >> >> Indeed, this commit explains it further: >> >> commit de1dd9fd2156874b45803299b3b27e65d5defdd9 >> regulator: core: Provide hints to the core about optional supplies >> >>> So we indeed should use devm_regulator_get() in this case. Thanks for > pointing out! >> >>>>> So in summary we only need AVDD switched for the GTA04 - but it does not >>>>> matter if the others are optional properties. We would not use them. >>>>> >>>>> It does matter if they are mandatory because it adds DT complexity (size >>>>> and processing) without added function. >>>> >>>> We should not be defining DT binding only with selected use cases/board >>>> designs in mind. IMO all three voltage supplies should be listed in the >>>> binding, presumably all can be made optional, with an assumption that when >>>> the property is missing selected pin is hooked up to a fixed regulator. >>> >>> Ok, then it should just be defined in the bindings but not used by >>> the driver? >> >> Yes, I think so. So we have a possibly complete binding right from the >> beginning. I someone needs handling other supplies than AVDD they could >> update the driver in future. > > Fine! I have sent some patches to Hughues so that he can integrate it in > his next version of the patch series. > > BR and thanks, > Nikolaus > OK got it, I'll push in v2.