From patchwork Thu Aug 13 10:18:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Young X-Patchwork-Id: 11712383 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8B0FE618 for ; Thu, 13 Aug 2020 10:18:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79DBF2080C for ; Thu, 13 Aug 2020 10:18:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726542AbgHMKSn (ORCPT ); Thu, 13 Aug 2020 06:18:43 -0400 Received: from gofer.mess.org ([88.97.38.141]:51487 "EHLO gofer.mess.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726053AbgHMKSn (ORCPT ); Thu, 13 Aug 2020 06:18:43 -0400 Received: by gofer.mess.org (Postfix, from userid 1000) id 4985FC63D7; Thu, 13 Aug 2020 11:18:41 +0100 (BST) From: Sean Young To: linux-media@vger.kernel.org Subject: [PATCH] media: gpio-ir-tx: spinlock is not needed to disable interrupts Date: Thu, 13 Aug 2020 11:18:41 +0100 Message-Id: <20200813101841.5526-1-sean@mess.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org During bit-banging the IR on a gpio pin, we cannot be scheduled or have anything interrupt us, else the generated signal will be incorrect. Therefore, we need to disable interrupts on the local cpu. This also disables preemption. local_irq_disable() does exactly what we need and does not require a spinlock. Signed-off-by: Sean Young Reported-by: kernel test robot --- drivers/media/rc/gpio-ir-tx.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) diff --git a/drivers/media/rc/gpio-ir-tx.c b/drivers/media/rc/gpio-ir-tx.c index f33b443bfa47..70d0d2baa3ae 100644 --- a/drivers/media/rc/gpio-ir-tx.c +++ b/drivers/media/rc/gpio-ir-tx.c @@ -19,8 +19,6 @@ struct gpio_ir { struct gpio_desc *gpio; unsigned int carrier; unsigned int duty_cycle; - /* we need a spinlock to hold the cpu while transmitting */ - spinlock_t lock; }; static const struct of_device_id gpio_ir_tx_of_match[] = { @@ -53,12 +51,11 @@ static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier) static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf, uint count) { - unsigned long flags; ktime_t edge; s32 delta; int i; - spin_lock_irqsave(&gpio_ir->lock, flags); + local_irq_disable(); edge = ktime_get(); @@ -72,14 +69,11 @@ static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf, } gpiod_set_value(gpio_ir->gpio, 0); - - spin_unlock_irqrestore(&gpio_ir->lock, flags); } static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf, uint count) { - unsigned long flags; ktime_t edge; /* * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on @@ -95,7 +89,7 @@ static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf, space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) * (NSEC_PER_SEC / 100), gpio_ir->carrier); - spin_lock_irqsave(&gpio_ir->lock, flags); + local_irq_disable(); edge = ktime_get(); @@ -128,19 +122,20 @@ static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf, edge = last; } } - - spin_unlock_irqrestore(&gpio_ir->lock, flags); } static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf, unsigned int count) { struct gpio_ir *gpio_ir = dev->priv; + unsigned long flags; + local_irq_save(flags); if (gpio_ir->carrier) gpio_ir_tx_modulated(gpio_ir, txbuf, count); else gpio_ir_tx_unmodulated(gpio_ir, txbuf, count); + local_irq_restore(flags); return count; }