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 X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9D2ADC4CEC9 for ; Fri, 20 Sep 2019 12:30:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64F4B2173E for ; Fri, 20 Sep 2019 12:30:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="g6ERzpJL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2409007AbfITMaL (ORCPT ); Fri, 20 Sep 2019 08:30:11 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:36404 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404361AbfITMaL (ORCPT ); Fri, 20 Sep 2019 08:30:11 -0400 Received: from lelv0265.itg.ti.com ([10.180.67.224]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id x8KCU2YC033049; Fri, 20 Sep 2019 07:30:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1568982602; bh=Ol6M1ir1cCrFdmazeVk2q4bf7wGJSKlf95XAGkQx4QI=; h=Subject:To:CC:References:From:Date:In-Reply-To; b=g6ERzpJLElkXyrwSOCdMpa7F1RcjgTNgqoC+4auEB6mhfweL9MVlnHxcYuu4uorgO dEuVOG9IUnsqWNRKO4/gSW/+qnBCev1RV9dpzJs17FOWNY34+cTyDR4HwJd0MT/IOt ADi2t+SMA5Jh6YGisQvtGT3gz+kAI1dnbB7B/1Rs= Received: from DLEE115.ent.ti.com (dlee115.ent.ti.com [157.170.170.26]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id x8KCU2G7130077 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 20 Sep 2019 07:30:02 -0500 Received: from DLEE111.ent.ti.com (157.170.170.22) by DLEE115.ent.ti.com (157.170.170.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5; Fri, 20 Sep 2019 07:30:02 -0500 Received: from fllv0039.itg.ti.com (10.64.41.19) by DLEE111.ent.ti.com (157.170.170.22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5 via Frontend Transport; Fri, 20 Sep 2019 07:29:58 -0500 Received: from [10.250.98.129] (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0039.itg.ti.com (8.15.2/8.15.2) with ESMTP id x8KCU0tP108372; Fri, 20 Sep 2019 07:30:00 -0500 Subject: Re: [PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core To: Jacek Anaszewski , , , , CC: , , , References: <20190717135948.19340-1-jjhiblot@ti.com> <20190717135948.19340-3-jjhiblot@ti.com> <4bd3b558-ea5b-0d2e-16b2-5b2e8bb484d2@gmail.com> <49152281-059c-6006-4c0f-a6be96a12707@ti.com> <928fd71b-d1d3-cbf3-1aed-ae7fa97f6cf0@gmail.com> From: Jean-Jacques Hiblot Message-ID: Date: Fri, 20 Sep 2019 14:29:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <928fd71b-d1d3-cbf3-1aed-ae7fa97f6cf0@gmail.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jacek, On 18/07/2019 19:49, Jacek Anaszewski wrote: > On 7/18/19 3:31 PM, Jean-Jacques Hiblot wrote: >> On 18/07/2019 14:24, Jacek Anaszewski wrote: >>> Hi Jean, >>> >>> Thank you for the updated patch set. >>> >>> I have some more comments below. >>> >>> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote: >>>>   +static bool __led_need_regulator_update(struct led_classdev >>>> *led_cdev, >>>> +                    int brightness) >>>> +{ >>>> +    bool new_state = (brightness != LED_OFF); >>> How about: >>> >>> bool new_state = !!brightness; >> Throughout the code LED_OFF is used when the LED is turned off. I think >> it would be more consistent to use it there too. > Basically brightness is a scalar and 0 always means off. > We treat enum led_brightness as a legacy type - it is no > longer valid on the whole its span since LED_FULL = 255 > was depreciated with addition of max_brightness property. > > IMHO use of reverse logic here only hinders code analysis. > >>>> + >>>> +    return led_cdev->regulator && led_cdev->regulator_state != >>>> new_state; >>>> +} >>>> +static int __led_handle_regulator(struct led_classdev *led_cdev, >>>> +                int brightness) >>>> +{ >>>> +    int rc; >>>> + >>>> +    if (__led_need_regulator_update(led_cdev, brightness)) { >>>> + >>>> +        if (brightness != LED_OFF) >>>> +            rc = regulator_enable(led_cdev->regulator); >>>> +        else >>>> +            rc = regulator_disable(led_cdev->regulator); >>>> +        if (rc) >>>> +            return rc; >>>> + >>>> +        led_cdev->regulator_state = (brightness != LED_OFF); >>>> +    } >>>> +    return 0; >>>> +} >>> Let's have these function names without leading underscores. >> OK. >>>>   static int __led_set_brightness(struct led_classdev *led_cdev, >>>>                   enum led_brightness value) >>>>   { >>>> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct >>>> work_struct *ws) >>>>       if (ret == -ENOTSUPP) >>>>           ret = __led_set_brightness_blocking(led_cdev, >>>>                       led_cdev->delayed_set_value); >>>> +    __led_handle_regulator(led_cdev, led_cdev->delayed_set_value) >>> If you called it from __led_set_brightness() and >> We cannot call it from __led_set_brightness() because it is supposed not >> to block. > You're right. The problematic part is that with regulator handling > we cannot treat the whole brightness setting operation uniformly > for brightness_set op case, i.e. without mediation of a workqueue. > > Now you have to fire workqueue in led_set_brightness_nopm() > even for brightness_set() op path, if regulator state needs update. > This is ugly and can be misleading. Can be also error prone and > have non-obvious implications for software blink state transitions. Taking your queue I reworked the series to take better care of the concurrency issues. I believe it's in better shape right now. > > I think we would first need to improve locking between the workqueue > and led_timer_function(). I proposed a patch [0] over a year > ago. I tried the patch and get a lot of warning because of triggers on storage devices. Making led_set_brightness() not callable from a IRQ context, is probably not the right approach anymore. JJ > > Only then we could think of adding another asynchronous dependency > to the brightness setting chain. > > [0] https://lkml.org/lkml/2018/1/17/1144 >