From patchwork Wed May 6 10:42:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Young X-Patchwork-Id: 209924 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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 9B452C38A2A for ; Wed, 6 May 2020 10:42:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8625520663 for ; Wed, 6 May 2020 10:42:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729174AbgEFKmZ (ORCPT ); Wed, 6 May 2020 06:42:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1725824AbgEFKmZ (ORCPT ); Wed, 6 May 2020 06:42:25 -0400 Received: from gofer.mess.org (gofer.mess.org [IPv6:2a02:8011:d000:212::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2BC4C061A0F for ; Wed, 6 May 2020 03:42:24 -0700 (PDT) Received: by gofer.mess.org (Postfix, from userid 1000) id 931E7C6372; Wed, 6 May 2020 11:42:22 +0100 (BST) From: Sean Young To: linux-media@vger.kernel.org Subject: [PATCH 1/2] media: rc: improve precision of transmitted signal due to scheduling Date: Wed, 6 May 2020 11:42:21 +0100 Message-Id: <20200506104222.16188-1-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 usleep_range() may take longer than the max argument due to scheduling, especially under load. This is causing random errors in the transmitted IR. Remove the usleep_range() in favour of busy-looping with ndelay(). Signed-off-by: Sean Young --- drivers/media/rc/gpio-ir-tx.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/drivers/media/rc/gpio-ir-tx.c b/drivers/media/rc/gpio-ir-tx.c index 18ca12d78314c..66703989ae185 100644 --- a/drivers/media/rc/gpio-ir-tx.c +++ b/drivers/media/rc/gpio-ir-tx.c @@ -79,13 +79,8 @@ static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf, // space edge = ktime_add_us(edge, txbuf[i]); delta = ktime_us_delta(edge, ktime_get()); - if (delta > 10) { - spin_unlock_irqrestore(&gpio_ir->lock, flags); - usleep_range(delta, delta + 10); - spin_lock_irqsave(&gpio_ir->lock, flags); - } else if (delta > 0) { + if (delta > 0) udelay(delta); - } } else { // pulse ktime_t last = ktime_add_us(edge, txbuf[i]);