From patchwork Mon Apr 20 12:38:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 227386 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 C7E7BC3A5A0 for ; Mon, 20 Apr 2020 13:00:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7D41206DD for ; Mon, 20 Apr 2020 13:00:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587387605; bh=YMFdLjTiqvREH9qsLeoZ6Ek6B94lsHuwlxz7QT5Acaw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xBjF47Gn7lZfNEkQEwLT7EjTAAGD47fIU05Eoc3+ordb3cYmeCUBqBsjDS74g4Ja9 w4qlp8H1naqMu7RTWdLh6YKlqzP285OA9JbPJV/W8ItBpxwK/iJxcNroQOdQ4fsj78 wEehvJmxWWWFapCc4QFkP0AYlkO7K3WUXgCrx7WI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727863AbgDTMkw (ORCPT ); Mon, 20 Apr 2020 08:40:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:33298 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727857AbgDTMku (ORCPT ); Mon, 20 Apr 2020 08:40:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 38F8E2070B; Mon, 20 Apr 2020 12:40:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386449; bh=YMFdLjTiqvREH9qsLeoZ6Ek6B94lsHuwlxz7QT5Acaw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BnXZEfU/K+noThR4S+kFC5MxGhShg6T2nqGvT7WRVCnkbH5Vr0wujKUt8LcLuYODZ LoyKGLs43zL122YqvP0li1BNonauo4DAsRJjmo5YflR/o1alwFdLj+qpQ3rdswe9vI s2XYAPqBN73ESJGwmDqr/EbRDQCcg63hw7U3Umx0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, YueHaibing , Mika Westerberg , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , Sven Van Asbroeck , Clemens Gruber , Thierry Reding Subject: [PATCH 5.5 27/65] pwm: pca9685: Fix PWM/GPIO inter-operation Date: Mon, 20 Apr 2020 14:38:31 +0200 Message-Id: <20200420121512.063188836@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200420121505.909671922@linuxfoundation.org> References: <20200420121505.909671922@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Sven Van Asbroeck commit 9cc5f232a4b6a0ef6e9b57876d61b88f61bdd7c2 upstream. This driver allows pwms to be requested as gpios via gpiolib. Obviously, it should not be allowed to request a GPIO when its corresponding PWM is already requested (and vice versa). So it requires some exclusion code. Given that the PWMm and GPIO cores are not synchronized with respect to each other, this exclusion code will also require proper synchronization. Such a mechanism was in place, but was inadvertently removed by Uwe's clean-up in commit e926b12c611c ("pwm: Clear chip_data in pwm_put()"). Upon revisiting the synchronization mechanism, we found that theoretically, it could allow two threads to successfully request conflicting PWMs/GPIOs. Replace with a bitmap which tracks PWMs in-use, plus a mutex. As long as PWM and GPIO's respective request/free functions modify the in-use bitmap while holding the mutex, proper synchronization will be guaranteed. Reported-by: YueHaibing Fixes: e926b12c611c ("pwm: Clear chip_data in pwm_put()") Cc: Mika Westerberg Cc: Uwe Kleine-König Cc: YueHaibing Link: https://lkml.org/lkml/2019/5/31/963 Signed-off-by: Sven Van Asbroeck Reviewed-by: Mika Westerberg [cg: Tested on an i.MX6Q board with two NXP PCA9685 chips] Tested-by: Clemens Gruber Reviewed-by: Sven Van Asbroeck # cg's rebase Link: https://lore.kernel.org/lkml/20200330160238.GD2817345@ulmo/ Signed-off-by: Thierry Reding Signed-off-by: Greg Kroah-Hartman --- drivers/pwm/pwm-pca9685.c | 85 +++++++++++++++++++++++++--------------------- 1 file changed, 48 insertions(+), 37 deletions(-) --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -20,6 +20,7 @@ #include #include #include +#include /* * Because the PCA9685 has only one prescaler per chip, changing the period of @@ -74,6 +75,7 @@ struct pca9685 { #if IS_ENABLED(CONFIG_GPIOLIB) struct mutex lock; struct gpio_chip gpio; + DECLARE_BITMAP(pwms_inuse, PCA9685_MAXCHAN + 1); #endif }; @@ -83,51 +85,51 @@ static inline struct pca9685 *to_pca(str } #if IS_ENABLED(CONFIG_GPIOLIB) -static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset) +static bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, int pwm_idx) { - struct pca9685 *pca = gpiochip_get_data(gpio); - struct pwm_device *pwm; + bool is_inuse; mutex_lock(&pca->lock); - - pwm = &pca->chip.pwms[offset]; - - if (pwm->flags & (PWMF_REQUESTED | PWMF_EXPORTED)) { - mutex_unlock(&pca->lock); - return -EBUSY; + if (pwm_idx >= PCA9685_MAXCHAN) { + /* + * "all LEDs" channel: + * pretend already in use if any of the PWMs are requested + */ + if (!bitmap_empty(pca->pwms_inuse, PCA9685_MAXCHAN)) { + is_inuse = true; + goto out; + } + } else { + /* + * regular channel: + * pretend already in use if the "all LEDs" channel is requested + */ + if (test_bit(PCA9685_MAXCHAN, pca->pwms_inuse)) { + is_inuse = true; + goto out; + } } - - pwm_set_chip_data(pwm, (void *)1); - + is_inuse = test_and_set_bit(pwm_idx, pca->pwms_inuse); +out: mutex_unlock(&pca->lock); - pm_runtime_get_sync(pca->chip.dev); - return 0; + return is_inuse; } -static bool pca9685_pwm_is_gpio(struct pca9685 *pca, struct pwm_device *pwm) +static void pca9685_pwm_clear_inuse(struct pca9685 *pca, int pwm_idx) { - bool is_gpio = false; - mutex_lock(&pca->lock); + clear_bit(pwm_idx, pca->pwms_inuse); + mutex_unlock(&pca->lock); +} - if (pwm->hwpwm >= PCA9685_MAXCHAN) { - unsigned int i; - - /* - * Check if any of the GPIOs are requested and in that case - * prevent using the "all LEDs" channel. - */ - for (i = 0; i < pca->gpio.ngpio; i++) - if (gpiochip_is_requested(&pca->gpio, i)) { - is_gpio = true; - break; - } - } else if (pwm_get_chip_data(pwm)) { - is_gpio = true; - } +static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset) +{ + struct pca9685 *pca = gpiochip_get_data(gpio); - mutex_unlock(&pca->lock); - return is_gpio; + if (pca9685_pwm_test_and_set_inuse(pca, offset)) + return -EBUSY; + pm_runtime_get_sync(pca->chip.dev); + return 0; } static int pca9685_pwm_gpio_get(struct gpio_chip *gpio, unsigned int offset) @@ -162,6 +164,7 @@ static void pca9685_pwm_gpio_free(struct pca9685_pwm_gpio_set(gpio, offset, 0); pm_runtime_put(pca->chip.dev); + pca9685_pwm_clear_inuse(pca, offset); } static int pca9685_pwm_gpio_get_direction(struct gpio_chip *chip, @@ -213,12 +216,17 @@ static int pca9685_pwm_gpio_probe(struct return devm_gpiochip_add_data(dev, &pca->gpio, pca); } #else -static inline bool pca9685_pwm_is_gpio(struct pca9685 *pca, - struct pwm_device *pwm) +static inline bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, + int pwm_idx) { return false; } +static inline void +pca9685_pwm_clear_inuse(struct pca9685 *pca, int pwm_idx) +{ +} + static inline int pca9685_pwm_gpio_probe(struct pca9685 *pca) { return 0; @@ -402,7 +410,7 @@ static int pca9685_pwm_request(struct pw { struct pca9685 *pca = to_pca(chip); - if (pca9685_pwm_is_gpio(pca, pwm)) + if (pca9685_pwm_test_and_set_inuse(pca, pwm->hwpwm)) return -EBUSY; pm_runtime_get_sync(chip->dev); @@ -411,8 +419,11 @@ static int pca9685_pwm_request(struct pw static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm) { + struct pca9685 *pca = to_pca(chip); + pca9685_pwm_disable(chip, pwm); pm_runtime_put(chip->dev); + pca9685_pwm_clear_inuse(pca, pwm->hwpwm); } static const struct pwm_ops pca9685_pwm_ops = {