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 7D4AFC433E2 for ; Sat, 12 Sep 2020 22:53:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3047921707 for ; Sat, 12 Sep 2020 22:53:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="IIBV5CQW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725914AbgILWxN (ORCPT ); Sat, 12 Sep 2020 18:53:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725907AbgILWxJ (ORCPT ); Sat, 12 Sep 2020 18:53:09 -0400 Received: from mail-oi1-x244.google.com (mail-oi1-x244.google.com [IPv6:2607:f8b0:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26E73C061574 for ; Sat, 12 Sep 2020 15:53:07 -0700 (PDT) Received: by mail-oi1-x244.google.com with SMTP id x19so13496479oix.3 for ; Sat, 12 Sep 2020 15:53:06 -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=cz7l4bGKHxfOKLLWHxTc5xdJem1sy7MolpQaLjxPyvs=; b=IIBV5CQWWCEP4EhPOxuW3YsT6AjNbySc01Z76A7uG2S5Jzq2vxIBtlFKOh3c2PVluN 6Q+8a8JxTNnLL1pAtN5w+bcInwxcSBKcxQ8oj/OLTJuJ33vqYS8ApCil3XyXgRaUx1Fy 3WulOIghHJJWVtNcOFFrv3sc1o+anGkVrFXKMBrWA4mKKpnmItDpFOeY/KRjJ+T2tG5X 8muMim8x7c1YuF8u/MszgIIoKoW7Ln1/A8F2CNBlD9xTHWPpRERb/CT5ipz8pMKoE0Ku 2ORt0iLHrXk0JqyNfcIG9vc2ILu++sS0LkrerBC0v4i5k8QCCzGBV/Jqt1zeuDpaPZi8 CpLw== 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=cz7l4bGKHxfOKLLWHxTc5xdJem1sy7MolpQaLjxPyvs=; b=K/OHHLsttoDu7YPN9aVhIzS2+CDKl0ndK7UTfeT/KRdLz4ZpIOcg0Tk+Cmr28NRwV3 G4i4iVcz+c0d48Bg5E45/Tj0r3mVu2zUW7GjS7VRh2cQUhmOh+SvnlGB80xFXO4t1u4l 5JlLi/c++HXtABTWy9Y7O8b0Wa2OrTn6t/kdRjm/ZWIhtTJPN77upgDa+JSMpS1Wp0OA cgYVzKLLQjB2HeS8vfYlMVMyac0hj68GL1SdSVCDXIn2HNVoM0GCNV6+mFwH+K6XO7HA rOvEHGcLZy/OJyDzXNowje8Bil9vlm8Ays4YIudxOMoJD/f3//CNXMx/+44BBScMpioD TkXg== X-Gm-Message-State: AOAM530kqj8lhi33sCgbdJOt5QGPTYG6xGyniTa7rEZIiEceGZKFxMfM 74PeW3q9Jz9hRJkm5StWVO/N3g== X-Google-Smtp-Source: ABdhPJzz+WfOASs3fCTMejIUiZxcNkVCEBQZAPhC2t4wyDdxudf/q6ZNd/UCcJKeUAn8xAUTMyZuuw== X-Received: by 2002:aca:c5cd:: with SMTP id v196mr5077895oif.63.1599951186236; Sat, 12 Sep 2020 15:53:06 -0700 (PDT) Received: from yoga ([2605:6000:e5cb:c100:8898:14ff:fe6d:34e]) by smtp.gmail.com with ESMTPSA id l5sm1027934otj.40.2020.09.12.15.53.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Sep 2020 15:53:05 -0700 (PDT) Date: Sat, 12 Sep 2020 17:53:02 -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 1/3] spi: spi-geni-qcom: Use the FIFO even more Message-ID: <20200912225302.GA3715@yoga> References: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 12 Sep 16:07 CDT 2020, Douglas Anderson wrote: > In commit 902481a78ee4 ("spi: spi-geni-qcom: Actually use our FIFO") I > explained that the maximum size we could program the FIFO was > "mas->tx_fifo_depth - 3" but that I chose "mas->tx_fifo_depth()" > because I was worried about decreased bandwidth. > > Since that time: > * All the interconnect patches have landed, making things run at the > proper speed. > * I've done more measurements. > > This lets me confirm that there's really no downside of using the FIFO > more. Specifically I did "flashrom -p ec -r /tmp/foo.bin" on a > Chromebook and averaged over several runs. Wouldn't there be a downside in the form of setting the watermark that close to the full FIFO we have less room for being late handling the interrupt? Or is there some mechanism involved that will prevent the FIFO from being overrun? Regards, Bjorn > > Before: It took 6.66 seconds and 59669 interrupts fired. > After: It took 6.66 seconds and 47992 interrupts fired. > > Signed-off-by: Douglas Anderson > --- > > drivers/spi/spi-geni-qcom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c > index 0dc3f4c55b0b..7f0bf0dec466 100644 > --- a/drivers/spi/spi-geni-qcom.c > +++ b/drivers/spi/spi-geni-qcom.c > @@ -308,7 +308,7 @@ static int spi_geni_init(struct spi_geni_master *mas) > * Hardware programming guide suggests to configure > * RX FIFO RFR level to fifo_depth-2. > */ > - geni_se_init(se, mas->tx_fifo_depth / 2, mas->tx_fifo_depth - 2); > + geni_se_init(se, mas->tx_fifo_depth - 3, mas->tx_fifo_depth - 2); > /* Transmit an entire FIFO worth of data per IRQ */ > mas->tx_wm = 1; > ver = geni_se_get_qup_hw_version(se); > -- > 2.28.0.618.gf4bc123cb7-goog >