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[188.217.56.12]) by smtp.gmail.com with ESMTPSA id i67-20020a1c3b46000000b003b492753826sm12485057wma.43.2022.09.19.00.11.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Sep 2022 00:11:12 -0700 (PDT) Date: Mon, 19 Sep 2022 09:11:10 +0200 From: Tommaso Merciai To: Sakari Ailus Cc: Mikhail Rudenko , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Hans Verkuil , Jacopo Mondi , Shawn Tu , Randy Dunlap , Daniel Scally , Christian Hemp , Laurent Pinchart , Marek Vasut , linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] media: i2c: add support for ov4689 Message-ID: <20220919071110.GB3958@tom-ThinkPad-T14s-Gen-2i> References: <20220911200147.375198-1-mike.rudenko@gmail.com> <20220911200147.375198-3-mike.rudenko@gmail.com> <20220914155122.GA9874@tom-ThinkPad-T14s-Gen-2i> <87k064pa2v.fsf@gmail.com> <20220916133401.GB2701@tom-ThinkPad-T14s-Gen-2i> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sakari, On Mon, Sep 19, 2022 at 06:33:12AM +0000, Sakari Ailus wrote: > Hi Tommaso, > > On Fri, Sep 16, 2022 at 03:34:01PM +0200, Tommaso Merciai wrote: > > > >> + ret = clk_set_rate(ov4689->xvclk, OV4689_XVCLK_FREQ); > > > >> + if (ret < 0) { > > > >> + dev_err(dev, "Failed to set xvclk rate (24MHz)\n"); > > > >> + return ret; > > > >> + } > > > >> + if (clk_get_rate(ov4689->xvclk) != OV4689_XVCLK_FREQ) > > > >> + dev_warn(dev, "xvclk mismatched, modes are based on 24MHz\n"); > > > > > > > > > > > > What do you think about? > > > > Thanks. > > > > > > Unfortunately, I have no experience with ACPI-based devices. :( > > > > > > Do you mean that in the case of an ACPI device and devm_clk_get_optional > > > returning NULL we should assume that the clock is already enabled and > > > will stay enabled during sensor operation? How should we distinguish it > > > from the case of an OF-based system and clock just missing from device > > > tree? > > > > Not exaclty :) > > > > I copy comment from [1] > > > > if you use ov5693->xvclk to identify the ACPI vs OF use case shouldn't > > you use the get_optionl() version ? Otherwise in the ACPI case you will have > > -ENOENT if there's not 'xvclk' property and bail out. > > > > Unless my understanding is wrong on ACPI we have "clock-frequency" and > > on OF "xvclk" with an "assigned-clock-rates", > > Generally yes. It's also possible to have a clock in ACPI based system > although those clocks do not come from ACPI. See e.g. > drivers/platform/x86/intel/int3472/clk_and_regulator.c . I save this :) Thanks for sharing. Regards, Tommaso > > -- > Sakari Ailus -- Tommaso Merciai Embedded Linux Engineer tommaso.merciai@amarulasolutions.com __________________________________ Amarula Solutions SRL Via Le Canevare 30, 31100 Treviso, Veneto, IT T. +39 042 243 5310 info@amarulasolutions.com www.amarulasolutions.com