Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751572AbdF1JNZ (ORCPT ); Wed, 28 Jun 2017 05:13:25 -0400 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.161]:14219 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751491AbdF1JNS (ORCPT ); Wed, 28 Jun 2017 05:13:18 -0400 X-RZG-AUTH: :JGIXVUS7cutRB/49FwqZ7WcecEarQROEYabkiUo6mSAGQ+qKID8zPH8HfA== X-RZG-CLASS-ID: mo00 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH v1 1/6] DT bindings: add bindings for ov965x camera module From: "H. Nikolaus Schaller" In-Reply-To: Date: Wed, 28 Jun 2017 11:12:38 +0200 Cc: Hugues FRUCHET , 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 Message-Id: <6F68CD33-70E6-47C1-9E89-5E2AA776879F@goldelico.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> To: Sylwester Nawrocki X-Mailer: Apple Mail (2.3124) 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 quoted-printable to 8bit by mail.home.local id v5S9DTFZ011446 Content-Length: 3500 Lines: 83 > 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. 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? BR and thanks, Nikolaus