From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5B5FC4332F for ; Tue, 26 Apr 2022 06:42:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245695AbiDZGqB (ORCPT ); Tue, 26 Apr 2022 02:46:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245658AbiDZGp6 (ORCPT ); Tue, 26 Apr 2022 02:45:58 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 276B213E1A; Mon, 25 Apr 2022 23:42:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C630DB81C58; Tue, 26 Apr 2022 06:42:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60CB6C385A0; Tue, 26 Apr 2022 06:42:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650955360; bh=Qj1iBgDmQNO80MoLSfQRprtZnwXJZ3zOv82xv0l0JOk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Nyia3qPWjSPOI+GpHMP1BShry0rDvyRrd+RsE8vQ4OOFPjybgraCtD/fqtcN6yOCV iqV9edZMMR5kNTVGkliDraRWGpYShEGd2G/s1oG6z+Oo3rirv+UjwI2TSwUeVc1xeX 5QIWFlKOad1wTwqb9Dp6X5yvz3LX/Vuv94P0Sb3VwIk/SHovMVa/qRGG3GQlRRwDqO 7i2xC5b4+jWfRwHo3hCC4wPeyxaDRVOp70wRXvbc8kwFeLb0USLzAfXknK03R7WTS0 TtkaGeKOi1FTVQD8AfonZD17tzZVqAtd/hrPDoBgvERjJI5CoaxrgOnd21BBucm6kw 0GGKivNxOCnCA== Message-ID: <89f7d69a-4fc8-33cc-d9ca-5c50dc5381ab@kernel.org> Date: Tue, 26 Apr 2022 09:42:31 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH 1/2] dt-bindings: usb: tps6598x: Make the interrupts property optional Content-Language: en-US To: Aswath Govindraju , "heikki.krogerus@linux.intel.com" Cc: Vignesh Raghavendra , Kishon Vijay Abraham I , Greg Kroah-Hartman , Rob Herring , Krzysztof Kozlowski , Heikki Krogerus , Sven Peter , Alyssa Rosenzweig , Hector Martin , Martin Kepplinger , Bryan O'Donoghue , linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220414083120.22535-1-a-govindraju@ti.com> <20220414083120.22535-2-a-govindraju@ti.com> <56c72151-af5f-366b-b17f-24b9fb6264da@ti.com> From: Roger Quadros In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 22/04/2022 08:07, Aswath Govindraju wrote: > Hi Roger, > > On 21/04/22 00:46, Roger Quadros wrote: >> Hi, >> >> On 18/04/2022 08:19, Aswath Govindraju wrote: >>> Hi Roger, >>> >>> On 14/04/22 23:40, Roger Quadros wrote: >>>> Hi, >>>> >>>> On 14/04/2022 11:31, Aswath Govindraju wrote: >>>>> Support for polling has been added in the driver, which will be used by >>>>> default if interrupts property is not populated. Therefore, remove >>>>> interrupts and interrupt-names from the required properties and add a note >>>>> under interrupts property describing the above support in driver. >>>>> >>>>> Suggested-by: Roger Quadros >>>> >>>> I did not suggest to make interrupts optional by default. >>>> >>>> What I suggested was that if a DT property exists to explicitly >>>> indicate polling mode then interrupts are not required. >>>> >>> >>> ohh okay, got it. However, may I know if adding a dt property to >>> indicate polling for aiding the driver, is the correct approach to model it? >>> >>> In terms of modelling hardware, as interrupts are not connected we are >>> not populating the interrupts property. Shouldn't that be all. If we are >>> adding a property explicitly to indicate polling that can be used by >>> driver, wouldn't that be a software aid being added in the device tree? >> >> The hardware (tps6598x chip) has an interrupt pin and is expected to be used >> in normal case. >> >> Some buggy boards might have forgot to connect it. We are adding polling mode only for these buggy boards. ;) >> So polling mode is an exception. >> > > Yes as you mentioned the interrupt line is expected to connected but > there could be cases where there are not enough pins on the SoC and > polling is used intentionally. In these cases this would be a feature > rather than a bug. I do not agree that this is a feature but a board defect. You can always use a GPIO expander to add more GPIOs than the SoC can provide. Type-C events are asynchronous and polling is a waste of CPU time. What will you do if system suspends and you need to wake up on Type-C status change? So polling mode is just an exception for the defective boards or could be used for debugging. > > Also, I feel like not adding interrupts property in the dt nodes will > indicate polling. My question is why are we adding an extra property > (which is being used only as an aid in the driver) when this feature can > be modeled by making interrupts property optional. Because interrupt property was not originally optional for this driver. I would like to hear what Heikki has to say about this. Any thoughts Heikki? cheers, -roger > > Thanks, > Aswath > >> cheers, >> -roger >> >>> >>> Thanks, >>> Aswath >>> >>>>> Signed-off-by: Aswath Govindraju >>>>> --- >>>>> Documentation/devicetree/bindings/usb/ti,tps6598x.yaml | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml b/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml >>>>> index a4c53b1f1af3..1c4b8c6233e5 100644 >>>>> --- a/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml >>>>> +++ b/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml >>>>> @@ -25,6 +25,8 @@ properties: >>>>> >>>>> interrupts: >>>>> maxItems: 1 >>>>> + description: >>>>> + If interrupts are not populated then by default polling will be used. >>>>> >>>>> interrupt-names: >>>>> items: >>>>> @@ -33,8 +35,6 @@ properties: >>>>> required: >>>>> - compatible >>>>> - reg >>>>> - - interrupts >>>>> - - interrupt-names >>>>> >>>>> additionalProperties: true >>>>> >>>> >>>> cheers, >>>> -roger > >