From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH V2] regulator: gpio: Reword the binding document References: <20190304194023.10926-1-marek.vasut@gmail.com> <834f8576-73a4-be0f-e322-91601bed5388@gmail.com> From: Marek Vasut Message-ID: <4d1cd905-c322-78e5-cb9c-dadba01b0324@gmail.com> Date: Tue, 5 Mar 2019 20:01:41 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit To: Harald Geyer Cc: devicetree@vger.kernel.org, Marek Vasut , Kuninori Morimoto , Linus Walleij , Mark Brown , Rob Herring , linux-renesas-soc@vger.kernel.org List-ID: On 3/5/19 5:10 PM, Harald Geyer wrote: > Marek Vasut writes: >> On 3/5/19 11:07 AM, Harald Geyer wrote: >>> marek.vasut@gmail.com writes: >>>> From: Marek Vasut >>>> >>>> Reword the binding document to make it clear how the propeties work >>>> and which properties affect which other properties. >>>> >>>> Signed-off-by: Marek Vasut >>>> Cc: Harald Geyer >>>> Cc: Kuninori Morimoto >>>> Cc: Linus Walleij >>>> Cc: Mark Brown >>>> Cc: Rob Herring >>>> Cc: linux-renesas-soc@vger.kernel.org >>>> To: devicetree@vger.kernel.org >>>> --- >>>> V2: - Make "gpios" a mandatory property >>>> - Reword "gpio-states" property description >>>> - Change "enable-gpio" to "enable-gpios" to match modern DT rules >>>> Note: The recent gpio-regulator rework caused breakage. While the >>>> changes in the gpio-regulator code were according to the DT >>>> binding document, they stopped working with older DTs. Make >>>> the binding document clearer to prevent such breakage in the >>>> future. >>> >>> Thanks for the update. I think it addresses all my concerns except for >>> one: >>> >>>> +- gpios-states : State of GPIO pins in "gpios" array that is set until >>>> + changed by the first consumer. 0: LOW, 1: HIGH. >>>> + Default is LOW if nothing else is specified. >>> >>> I still believe this not true: There is no guarantee that the regulator >>> core won't change the state of GPIO pins before the first consumer comes >>> up. >> >> Why would it do that ? > > Because the regulator core doesn't know about this driver specific > property at all. And without any constraints placed by consumers, the > core is free to choose any state whatsoever at any point in time. But git grep seems to disagree, see drivers/regulator/gpio-regulator.c: ret = of_property_read_u32_index(np, "gpios-states", i, The core sets the pins to such a value until the consumer takes over. >> That would completely invalidate any remaining >> useful-ness of this property. > > Yes, I believe this property is mostly useless. That's what I want to > get across with my wording proposal. The remaining usecase, that I can see, > is when the GPIOs have been setup by the bootloader and we don't want > to reset them to low during probing (which some OSes might be capable > of, but linux currently doesn't). Also a state of all GPIOs low might > be invalid (not in the "states" property), so we shouldn't set all GPIOs > to low during probing in that case. I presume the bootloader might even add this property to DT based on the state in which it leaves the GPIOs in. > HTH, > Harald > >>> I still think my proposal describes the property more acurately: >>> gpios-states : On operating systems, that don't support reading back gpio >>> values in output mode (most notably linux), this array >>> provides the state of GPIO pins set when requesting them >>> from the gpio controller. Systems, that are capable of >>> preserving state when requesting the lines, are free to >>> ignore this property. 0: LOW, 1: HIGH. Default is LOW if >>> nothing else is specified. >>> >>> Since we had this discussion already in the V1 thread and you clearly don't >>> agree with me, the maintainers will need to decide. You can add >>> Reviewed-by: Harald Geyer >>> once Rob and/or Mark have addressed this issue. >> >> I think we're just looking at this from two different perspectives and >> for whatever reason can't reconcile them. >> >>> Thanks for your work! >>> Harald >>> >> >> >> -- >> Best regards, >> Marek Vasut > -- Best regards, Marek Vasut