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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 29639C43461 for ; Sat, 12 Sep 2020 22:54:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7797214F1 for ; Sat, 12 Sep 2020 22:54:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="BXnhs5Cg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725924AbgILWyt (ORCPT ); Sat, 12 Sep 2020 18:54:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725907AbgILWyq (ORCPT ); Sat, 12 Sep 2020 18:54:46 -0400 Received: from mail-ot1-x342.google.com (mail-ot1-x342.google.com [IPv6:2607:f8b0:4864:20::342]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A50A1C061757 for ; Sat, 12 Sep 2020 15:54:45 -0700 (PDT) Received: by mail-ot1-x342.google.com with SMTP id e23so11535813otk.7 for ; Sat, 12 Sep 2020 15:54:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=OMKklbN2lN6kWblqLp/KhqeIKTNslngE7aod6/EqkYU=; b=BXnhs5CgD7Qi0bV003nPQQzi2g0RSJU+U1mYiNoXq1BisWvFct3wAMcEHNd7RbyErm jdXkCPRMft+mhPfXMCRkzwF+yWYzRo4SYFh7Jz9jt+c82ek0sheOziLgDKz35okSoyyu zNZkMRdmmMUTl6OKS0XqDhrEz42U0Wg/SkX/TKIZD4voxNTrQoW9mjhilyZBWfvf6j3i q7xTIbDrrtvIbmtRKk/+N9R8tfVqq+7tToYSbt7eBvt3kLHzdvYRz1xg3KJmycIWRPeB PIeor2yVS4ZR8OJRgP1tIs+yhotJ5SJcA57eKcRdzqbnKE1nKigebdpkxAczI44p+730 O1HQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=OMKklbN2lN6kWblqLp/KhqeIKTNslngE7aod6/EqkYU=; b=gLHUlEPzKxjkDCAKcniVWAFT6BVF2lAZzDKnhdTl2aXsZ/DNr1ezjfQB1C94RpK6Je 0aPr+ihWjJmSY3o42LZADwDktZP3Inw29VPLuCb9U78VkpBiYSc+KLT1W16topwOqxZe HC4Lx22psjkyyhqpC5YlX2AwAmJRSEzVDc51STrh3HZCYvmb/jipIJ+RuwXX6jNER6kU BX594DSsGm1pnco4fXbIfE3fSBwdx2yoUjgkpbNWZrHAY02FZ4+p2Qtz4IuLlxuDVgXZ cz/8imAqffeaENELRSPlwzHmBZevsy5cJWSnXCFeUmR8nZOJZC/8F6NPj+cPMnUiVX97 Jyqw== X-Gm-Message-State: AOAM530kurrYDu5Rdq8+/2/LpITbm81s9jFhkwv/V6AfIed1sVU8YQM1 xM38fJ+xv4SPzeYaPhl0yvKi9g== X-Google-Smtp-Source: ABdhPJzzH8/SJznN9BD+Ma54S3fyH71aziEkswAQB/2ch5l2Blw054vnEiqnttpfgI8XjDgypypaSA== X-Received: by 2002:a9d:66d4:: with SMTP id t20mr4850145otm.133.1599951283767; Sat, 12 Sep 2020 15:54:43 -0700 (PDT) Received: from yoga ([2605:6000:e5cb:c100:8898:14ff:fe6d:34e]) by smtp.gmail.com with ESMTPSA id d26sm1025568otl.10.2020.09.12.15.54.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Sep 2020 15:54:43 -0700 (PDT) Date: Sat, 12 Sep 2020 17:54:40 -0500 From: Bjorn Andersson To: Douglas Anderson Cc: Mark Brown , Akash Asthana , swboyd@chromium.org, Andy Gross , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH 3/3] spi: spi-geni-qcom: Slightly optimize setup of bidirectional xfters Message-ID: <20200912225440.GB3715@yoga> References: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid> <20200912140730.3.Ided778fb4cd078e36c6b240d1b279cd7a534a313@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200912140730.3.Ided778fb4cd078e36c6b240d1b279cd7a534a313@changeid> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 12 Sep 16:08 CDT 2020, Douglas Anderson wrote: > When setting up a bidirectional transfer we need to program both the > TX and RX lengths. We don't need a memory barrier between those two > writes. Factor out the __iowmb() and use writel_relaxed(). This > saves a fraction of a microsecond of setup overhead on bidirectional > transfers. > > Signed-off-by: Douglas Anderson > --- > > drivers/spi/spi-geni-qcom.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c > index 92d88bf85a90..6c7e12b68bf0 100644 > --- a/drivers/spi/spi-geni-qcom.c > +++ b/drivers/spi/spi-geni-qcom.c > @@ -376,15 +376,22 @@ static void setup_fifo_xfer(struct spi_transfer *xfer, > len &= TRANS_LEN_MSK; > > mas->cur_xfer = xfer; > + > + /* > + * Factor out the __iowmb() so that we can use writel_relaxed() for > + * both writes below and thus only incur the overhead once even if > + * we execute both of them. > + */ How many passes through this function do we have to take before saving the amount of time it took me to read this comment? Reviewed-by: Bjorn Andersson Regards, Bjorn > + __iowmb(); > + > if (xfer->tx_buf) { > m_cmd |= SPI_TX_ONLY; > mas->tx_rem_bytes = xfer->len; > - writel(len, se->base + SE_SPI_TX_TRANS_LEN); > + writel_relaxed(len, se->base + SE_SPI_TX_TRANS_LEN); > } > - > if (xfer->rx_buf) { > m_cmd |= SPI_RX_ONLY; > - writel(len, se->base + SE_SPI_RX_TRANS_LEN); > + writel_relaxed(len, se->base + SE_SPI_RX_TRANS_LEN); > mas->rx_rem_bytes = xfer->len; > } > > -- > 2.28.0.618.gf4bc123cb7-goog >