From patchwork Wed Jul 7 16:27:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 1501847 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4GKlH22WRQz9sWq for ; Thu, 8 Jul 2021 02:28:46 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230262AbhGGQbZ (ORCPT ); Wed, 7 Jul 2021 12:31:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230195AbhGGQbY (ORCPT ); Wed, 7 Jul 2021 12:31:24 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EFA5C061574 for ; Wed, 7 Jul 2021 09:28:43 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1m1APh-0003qC-QG; Wed, 07 Jul 2021 18:28:41 +0200 Received: from [2a0a:edc0:0:900:1d::77] (helo=ptz.office.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1m1APh-0002aq-0f; Wed, 07 Jul 2021 18:28:41 +0200 Received: from ukl by ptz.office.stw.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1m1APg-0006HE-WB; Wed, 07 Jul 2021 18:28:40 +0200 From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Thierry Reding , Lee Jones Cc: linux-pwm@vger.kernel.org, kernel@pengutronix.de, Sascha Hauer , Shawn Guo Subject: [PATCH 02/47] pwm: mxs: Don't modify HW state in .probe() after the PWM chip was registered Date: Wed, 7 Jul 2021 18:27:50 +0200 Message-Id: <20210707162835.1772882-3-u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210707162835.1772882-1-u.kleine-koenig@pengutronix.de> References: <20210707162835.1772882-1-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-pwm@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org This fixes a race condition: After pwmchip_add() is called there might already be a consumer and then modifying the hardware behind the consumer's back is bad. So reset before calling pwmchip_add(). Note that reseting the hardware isn't the right thing to do if the PWM is already running as it might e.g. disable (or even enable) a backlight that is supposed to be on (or off). Fixes: 4dce82c1e840 ("pwm: add pwm-mxs support") Cc: Sascha Hauer Cc: Shawn Guo Signed-off-by: Uwe Kleine-König --- drivers/pwm/pwm-mxs.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index a22180803bd7..558dc1de8f5d 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c @@ -145,6 +145,11 @@ static int mxs_pwm_probe(struct platform_device *pdev) return ret; } + /* FIXME: Only do this if the PWM isn't already running */ + ret = stmp_reset_block(mxs->base); + if (ret) + return dev_err_probe(&pdev->dev, ret, "failed to reset PWM\n"); + ret = pwmchip_add(&mxs->chip); if (ret < 0) { dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret); @@ -153,15 +158,7 @@ static int mxs_pwm_probe(struct platform_device *pdev) platform_set_drvdata(pdev, mxs); - ret = stmp_reset_block(mxs->base); - if (ret) - goto pwm_remove; - return 0; - -pwm_remove: - pwmchip_remove(&mxs->chip); - return ret; } static int mxs_pwm_remove(struct platform_device *pdev)