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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 2E9E6C433DF for ; Thu, 28 May 2020 13:11:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04EAC207F5 for ; Thu, 28 May 2020 13:11:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="d0Z/2UNj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390228AbgE1NLr (ORCPT ); Thu, 28 May 2020 09:11:47 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:38661 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390171AbgE1NLq (ORCPT ); Thu, 28 May 2020 09:11:46 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1590671505; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=5KCsj0GEfP6+olt7t0wTZsy18p2KiqTY5awAccURH8k=; b=d0Z/2UNjKRXpT75UfaxtYInVXR+GuKhx/K0xtBtR7Kn09Gz/LMoIp0NRDQRdV1s/E/HRaSM9 zj4l0fMxRRPcQTcMOnnhSjsapt5bMniIuQYqIGRDhNmLBc+I26TC26U/qNxkB/qdsVYObKgm 1G9LG94mhzi8i2SuCk3adGQI2+Q= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI0ZDgwZiIsICJsaW51eC1ncGlvQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n03.prod.us-west-2.postgun.com with SMTP id 5ecfb885c6d4683243305c55 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 28 May 2020 13:11:33 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 06B27C433C6; Thu, 28 May 2020 13:11:32 +0000 (UTC) Received: from [192.168.43.129] (unknown [106.222.4.139]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: mkshah) by smtp.codeaurora.org (Postfix) with ESMTPSA id CBE80C433C9; Thu, 28 May 2020 13:11:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org CBE80C433C9 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=mkshah@codeaurora.org Subject: Re: [PATCH v2 1/4] gpio: gpiolib: Allow GPIO IRQs to lazy disable To: Stephen Boyd , bjorn.andersson@linaro.org, evgreen@chromium.org, linus.walleij@linaro.org, maz@kernel.org, mka@chromium.org Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-gpio@vger.kernel.org, agross@kernel.org, tglx@linutronix.de, jason@lakedaemon.net, dianders@chromium.org, rnayak@codeaurora.org, ilina@codeaurora.org, lsrao@codeaurora.org References: <1590253873-11556-1-git-send-email-mkshah@codeaurora.org> <1590253873-11556-2-git-send-email-mkshah@codeaurora.org> <159057264232.88029.4708934729701385486@swboyd.mtv.corp.google.com> <4e070cda-8c22-c554-610e-172320045840@codeaurora.org> <159062812628.69627.2153485337510882984@swboyd.mtv.corp.google.com> From: Maulik Shah Message-ID: <948defc1-5ea0-adbb-185b-5f5a81f2e28a@codeaurora.org> Date: Thu, 28 May 2020 18:41:23 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <159062812628.69627.2153485337510882984@swboyd.mtv.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org Hi, On 5/28/2020 6:38 AM, Stephen Boyd wrote: > Quoting Maulik Shah (2020-05-27 04:26:14) >> On 5/27/2020 3:14 PM, Stephen Boyd wrote: >>> Quoting Maulik Shah (2020-05-23 10:11:10) >>>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c >>>> index eaa0e20..3810cd0 100644 >>>> --- a/drivers/gpio/gpiolib.c >>>> +++ b/drivers/gpio/gpiolib.c >>>> @@ -2465,32 +2465,37 @@ static void gpiochip_irq_relres(struct irq_data *d) >>>> gpiochip_relres_irq(gc, d->hwirq); >>>> } >>>> >>>> +static void gpiochip_irq_mask(struct irq_data *d) >>>> +{ >>>> + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); >>>> + >>>> + if (gc->irq.irq_mask) >>>> + gc->irq.irq_mask(d); >>>> + gpiochip_disable_irq(gc, d->hwirq); >>> How does this work in the lazy case when I want to drive the GPIO? Say I >>> have a GPIO that is also an interrupt. The code would look like >>> >>> struct gpio_desc *gpio = gpiod_get(...) >>> unsigned int girq = gpiod_to_irq(gpio) >>> >>> request_irq(girq, ...); >>> >>> disable_irq(girq); >>> gpiod_direction_output(gpio, 1); >>> >>> In the lazy case genirq wouldn't call the mask function until the first >>> interrupt arrived on the GPIO line. If that never happened then wouldn't >>> we be blocked in gpiod_direction_output() when the test_bit() sees >>> FLAG_USED_AS_IRQ? Or do we need irqs to be released before driving >>> gpios? >> The client driver can decide to unlazy disable IRQ with below API... >> >>  irq_set_status_flags(girq, IRQ_DISABLE_UNLAZY); >> >> This will immediatly invoke mask function (unlazy disable) from genirq, >> even though irq_disable is not implemented. >> > Sure a consumer can disable the lazy feature, but that shouldn't be > required to make this work. The flag was introduced in commit > e9849777d0e2 ("genirq: Add flag to force mask in > disable_irq[_nosync]()") specifically to help devices that can't disable > the interrupt in their own device avoid a double interrupt. i don't think this will be a problem. Case 1) Client driver have locked gpio to be used as IRQ using gpiochip_lock_as_irq() In this case, When client driver want to change the direction for a gpio, they will invoke gpiod_direction_output(). I see it checks for two flags (pasted below), if GPIO is used as IRQ and whether its enabled IRQ or not.        /* GPIOs used for enabled IRQs shall not be set as output */         if (test_bit(FLAG_USED_AS_IRQ, &desc->flags) &&             test_bit(FLAG_IRQ_IS_ENABLED, &desc->flags)) { The first one (FLAG_USED_AS_IRQ) is set only if client driver in past have locked gpio to use as IRQ with a call to gpiochip_lock_as_irq() then it never gets unlocked until clients invoke gpiochip_unlock_as_irq(). So i presume the client driver which in past locked gpio to be used as IRQ, now wants to change direction then it will a. first unlock to use as IRQ b. then change the direction. Once it unlocks in step (a), both these flags will be cleared and there won't be any error in changing direction in step (b). Case 2) Client driver did not lock gpio to be used as IRQ. In this case, it will be straight forward to change the direction, as FLAG_USED_AS_IRQ is never set. Thanks, Maulik -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation