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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED,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 48579C28CC1 for ; Sat, 1 Jun 2019 13:39:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 223F627606 for ; Sat, 1 Jun 2019 13:39:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559396369; bh=Abv9GsTyntkTHWoXQ9xFksd//sO3na6syWyCUco9TYM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=dj1YRFfBtT/Lh2ogEFDZC4KO4irO7dJGy1gdFg/e/Q/5d9rJLaudc7Oa8f515SpH0 S/mrXQwbg/1pWIHcBHR+qghTOzC3tkVAWIFu39n254w+C0SndMUHiZAaXylrRse1cE WJqplyR4R63L5Y4AldB7nlhSTN7zS6jxgakCbHVE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728799AbfFANj2 (ORCPT ); Sat, 1 Jun 2019 09:39:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:48522 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728423AbfFANVO (ORCPT ); Sat, 1 Jun 2019 09:21:14 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5D7CC27305; Sat, 1 Jun 2019 13:21:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395273; bh=Abv9GsTyntkTHWoXQ9xFksd//sO3na6syWyCUco9TYM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nLvN1nvhgifCYbcQSqBNxQUeZBs87/Z9erxQTK3Zuv654thsvp2E7GM/hodHdqpDq 4AJOmzayPTjLadEyaygpTg4iqHiyqhG/uK5McCSGLfzT8QDMp3apSxg7dVQlcJVAtO f5n2J0JcP/8M2vGjmd4xwR4DgAW9Tyb4ynQw35wU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Martin Blumenstingl , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Neil Armstrong , Thierry Reding , Sasha Levin , linux-pwm@vger.kernel.org, linux-amlogic@lists.infradead.org Subject: [PATCH AUTOSEL 5.0 037/173] pwm: meson: Use the spin-lock only to protect register modifications Date: Sat, 1 Jun 2019 09:17:09 -0400 Message-Id: <20190601131934.25053-37-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601131934.25053-1-sashal@kernel.org> References: <20190601131934.25053-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Martin Blumenstingl [ Upstream commit f173747fffdf037c791405ab4f1ec0eb392fc48e ] Holding the spin-lock for all of the code in meson_pwm_apply() can result in a "BUG: scheduling while atomic". This can happen because clk_get_rate() (which is called from meson_pwm_calc()) may sleep. Only hold the spin-lock when modifying registers to solve this. The reason why we need a spin-lock in the driver is because the REG_MISC_AB register is shared between the two channels provided by one PWM controller. The only functions where REG_MISC_AB is modified are meson_pwm_enable() and meson_pwm_disable() so the register reads/writes in there need to be protected by the spin-lock. The original code also used the spin-lock to protect the values in struct meson_pwm_channel. This could be necessary if two consumers can use the same PWM channel. However, PWM core doesn't allow this so we don't need to protect the values in struct meson_pwm_channel with a lock. Fixes: 211ed630753d2f ("pwm: Add support for Meson PWM Controller") Signed-off-by: Martin Blumenstingl Reviewed-by: Uwe Kleine-König Reviewed-by: Neil Armstrong Signed-off-by: Thierry Reding Signed-off-by: Sasha Levin --- drivers/pwm/pwm-meson.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c index c1ed641b3e266..f6e738ad7bd92 100644 --- a/drivers/pwm/pwm-meson.c +++ b/drivers/pwm/pwm-meson.c @@ -111,6 +111,10 @@ struct meson_pwm { const struct meson_pwm_data *data; void __iomem *base; u8 inverter_mask; + /* + * Protects register (write) access to the REG_MISC_AB register + * that is shared between the two PWMs. + */ spinlock_t lock; }; @@ -235,6 +239,7 @@ static void meson_pwm_enable(struct meson_pwm *meson, { u32 value, clk_shift, clk_enable, enable; unsigned int offset; + unsigned long flags; switch (id) { case 0: @@ -255,6 +260,8 @@ static void meson_pwm_enable(struct meson_pwm *meson, return; } + spin_lock_irqsave(&meson->lock, flags); + value = readl(meson->base + REG_MISC_AB); value &= ~(MISC_CLK_DIV_MASK << clk_shift); value |= channel->pre_div << clk_shift; @@ -267,11 +274,14 @@ static void meson_pwm_enable(struct meson_pwm *meson, value = readl(meson->base + REG_MISC_AB); value |= enable; writel(value, meson->base + REG_MISC_AB); + + spin_unlock_irqrestore(&meson->lock, flags); } static void meson_pwm_disable(struct meson_pwm *meson, unsigned int id) { u32 value, enable; + unsigned long flags; switch (id) { case 0: @@ -286,9 +296,13 @@ static void meson_pwm_disable(struct meson_pwm *meson, unsigned int id) return; } + spin_lock_irqsave(&meson->lock, flags); + value = readl(meson->base + REG_MISC_AB); value &= ~enable; writel(value, meson->base + REG_MISC_AB); + + spin_unlock_irqrestore(&meson->lock, flags); } static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, @@ -296,19 +310,16 @@ static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, { struct meson_pwm_channel *channel = pwm_get_chip_data(pwm); struct meson_pwm *meson = to_meson_pwm(chip); - unsigned long flags; int err = 0; if (!state) return -EINVAL; - spin_lock_irqsave(&meson->lock, flags); - if (!state->enabled) { meson_pwm_disable(meson, pwm->hwpwm); channel->state.enabled = false; - goto unlock; + return 0; } if (state->period != channel->state.period || @@ -329,7 +340,7 @@ static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, err = meson_pwm_calc(meson, channel, pwm->hwpwm, state->duty_cycle, state->period); if (err < 0) - goto unlock; + return err; channel->state.polarity = state->polarity; channel->state.period = state->period; @@ -341,9 +352,7 @@ static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, channel->state.enabled = true; } -unlock: - spin_unlock_irqrestore(&meson->lock, flags); - return err; + return 0; } static void meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, -- 2.20.1