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=-12.8 required=3.0 tests=BAYES_00,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 339DCC55179 for ; Tue, 27 Oct 2020 17:13:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D977D21D24 for ; Tue, 27 Oct 2020 17:13:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603818812; bh=DCzZ0UrLBx/7/+U1su7kKKXrchCNd0OY2Vrfii5s00Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=GGb9Lb3qPxUGoYSPJoWLupfBp35OGus1EP6qLxJDfBwrSphtzU46a52FdiuNP15LQ HH9ypl4bNnyjLgxMdb5joBhJumxfYb7e4YMVblKQYVrry1dQBJFXISciOiepXC+ebW BierFejz35ZBozAXKPg+O/7vKJCDizgbvzgya+jM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1817126AbgJ0RNb (ORCPT ); Tue, 27 Oct 2020 13:13:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:60948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1784613AbgJ0O7T (ORCPT ); Tue, 27 Oct 2020 10:59:19 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 5947D20714; Tue, 27 Oct 2020 14:59:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810758; bh=DCzZ0UrLBx/7/+U1su7kKKXrchCNd0OY2Vrfii5s00Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kJyT+26m1xZg/Bf5cxFut8X48StcoATJP9Yg4cb7AGqXQWQZd4xqNtO/N7xd0IA3E FWrRAvOeUMC6ixLLJZeAaIVrA9y/Yt86BG8uJgMz3K87vpjhiuoYNVxnNcjB2azxVH DxoKiYj2hJY0OIvO5X4z8djceU0rcCy5y9625m0M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Aswath Govindraju , Mark Brown , Sasha Levin Subject: [PATCH 5.8 254/633] spi: omap2-mcspi: Improve performance waiting for CHSTAT Date: Tue, 27 Oct 2020 14:49:57 +0100 Message-Id: <20201027135534.578929259@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135522.655719020@linuxfoundation.org> References: <20201027135522.655719020@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Aswath Govindraju [ Upstream commit 7b1d96813317358312440d0d07abbfbeb0ef8d22 ] This reverts commit 13d515c796 (spi: omap2-mcspi: Switch to readl_poll_timeout()). The amount of time spent polling for the MCSPI_CHSTAT bits to be set on AM335x-icev2 platform is less than 1us (about 0.6us) in most cases, with or without using DMA. So, in most cases the function need not sleep. Also, setting the sleep_usecs to zero would not be optimal here because ktime_add_us() used in readl_poll_timeout() is slower compared to the direct addition used after the revert. So, it is sub-optimal to use readl_poll_timeout in this case. When DMA is not enabled, this revert results in an increase of about 27% in throughput and decrease of about 20% in CPU usage. However, the CPU usage and throughput are almost the same when used with DMA. Therefore, fix this by reverting the commit which switched to using readl_poll_timeout(). Fixes: 13d515c796ad ("spi: omap2-mcspi: Switch to readl_poll_timeout()") Signed-off-by: Aswath Govindraju Link: https://lore.kernel.org/r/20200910122624.8769-1-a-govindraju@ti.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi-omap2-mcspi.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c index e9e256718ef4a..10d8a722b0833 100644 --- a/drivers/spi/spi-omap2-mcspi.c +++ b/drivers/spi/spi-omap2-mcspi.c @@ -24,7 +24,6 @@ #include #include #include -#include #include #include @@ -349,9 +348,19 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi, static int mcspi_wait_for_reg_bit(void __iomem *reg, unsigned long bit) { - u32 val; - - return readl_poll_timeout(reg, val, val & bit, 1, MSEC_PER_SEC); + unsigned long timeout; + + timeout = jiffies + msecs_to_jiffies(1000); + while (!(readl_relaxed(reg) & bit)) { + if (time_after(jiffies, timeout)) { + if (!(readl_relaxed(reg) & bit)) + return -ETIMEDOUT; + else + return 0; + } + cpu_relax(); + } + return 0; } static int mcspi_wait_for_completion(struct omap2_mcspi *mcspi, -- 2.25.1