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=-8.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 A8C4AC43613 for ; Thu, 20 Jun 2019 18:28:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 786012082C for ; Thu, 20 Jun 2019 18:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561055294; bh=pc85b4ajV0dySNWzhx4DlBu1LNQUg0RzGU5Vz1B6dXg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=RWrF9XmLA/Gy6qz5AjCKaMlnDbcbC9wFxtTr88g4vumJTEGEULS4dS81NPGhXdZo3 aGh6Bs8RNKy8CiA6TcooCIDoEeQLfY3nnf0qTIFUB9gaE3o7pMMGgKHJ7IJq20e3fN O5SCxF1hwM90XEuPEtna2aqRyZnW0xRI1J5fgp3U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725907AbfFTSEM (ORCPT ); Thu, 20 Jun 2019 14:04:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:56318 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727804AbfFTSEL (ORCPT ); Thu, 20 Jun 2019 14:04:11 -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 22EA721479; Thu, 20 Jun 2019 18:04:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561053850; bh=pc85b4ajV0dySNWzhx4DlBu1LNQUg0RzGU5Vz1B6dXg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P9SdlUoMMBZ7mvz1ch6brphwtuHDiObAtFrLm1IhWyIaK87eG52ta4D5gjud7XVtM UnnVOaUlVWyH7PL0nTGQuSAiGamU636RtxwaV57pclcUSl5wjMFlo5FYrSpgADMlYz 3FcemaFezzSzsZdW/e+tJT0kgHyfoyH6Edtg5nUQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martin Blumenstingl , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Neil Armstrong , Thierry Reding , Sasha Levin Subject: [PATCH 4.9 019/117] pwm: meson: Use the spin-lock only to protect register modifications Date: Thu, 20 Jun 2019 19:55:53 +0200 Message-Id: <20190620174353.144032070@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190620174351.964339809@linuxfoundation.org> References: <20190620174351.964339809@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ 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 9d5bd7d5c610..f58a4867b519 100644 --- a/drivers/pwm/pwm-meson.c +++ b/drivers/pwm/pwm-meson.c @@ -110,6 +110,10 @@ 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; }; @@ -230,6 +234,7 @@ 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: @@ -250,6 +255,8 @@ 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; @@ -262,11 +269,14 @@ 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: @@ -281,9 +291,13 @@ 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, @@ -291,19 +305,16 @@ 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 || @@ -324,7 +335,7 @@ 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; @@ -336,9 +347,7 @@ 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