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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 389BEC433E2 for ; Sun, 13 Sep 2020 03:13:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6B3920732 for ; Sun, 13 Sep 2020 03:13:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="lGSRcGwd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725925AbgIMDNJ (ORCPT ); Sat, 12 Sep 2020 23:13:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725908AbgIMDNA (ORCPT ); Sat, 12 Sep 2020 23:13:00 -0400 Received: from mail-oi1-x242.google.com (mail-oi1-x242.google.com [IPv6:2607:f8b0:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 86A6DC061573 for ; Sat, 12 Sep 2020 20:12:59 -0700 (PDT) Received: by mail-oi1-x242.google.com with SMTP id a3so13894802oib.4 for ; Sat, 12 Sep 2020 20:12:59 -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=+YxXUaWaUQYtZQa9Fpn0ZMzcxX/ZLEWMpqwg81RPTCA=; b=lGSRcGwdtrbBLQnfCW7ysJIYPg2WZH6Pwjc1/LIU8UVTGr9R3I2PKlzh88HCbokZaA J4rN5qjfVYZx4zypjp+BEQ/YGAgNHJdE8iPWwo807otrovEN1nv8EG7qvxBhVUdBKqLA Da94BT2Rss8Q3xnVsuAY5+ShPJ3Z3eEO3fDea4T022E+BMifXa2SP6aBtrU/b2WyVV2O H/ulCqOqDRZ1C/XfA008feYXhW9zf9DGruKZbY4auAS2IXjth8rOxr49F1hoFT0Ho1Ve e25VeCwsLQwAPRRwKsEMm6wWokkLpA+i+h5NxC/g1/3u9oJ8yo+xRoYWNolGsUoW3/GN MbnQ== 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=+YxXUaWaUQYtZQa9Fpn0ZMzcxX/ZLEWMpqwg81RPTCA=; b=muHgjAKfwx4M9kNnPAg9jWlN4SMaAQXUEEbXDep9DeTUPobzmckIgLGwc9GiETR6dr UdMnhvub0gPUK5et8UEZWOMHksGAIi02q5zj41joDHQu/3hpOfaej4vGxeje4cfGZWvF rEoRz+awbXi8Nl9cBlCkxiNgpOKCknSe9eB78DB+X9GuhDGOtzfFRZzyGOwZlb97wdgB 2QItRLdabonZNVgehWOa0Kv0ih8s9w1vhlQ8S5OWWEo7HS2Y5R09XGixtrRlpYL1O2Bp yRPKXWMHaveUfW9ROb/KkI30wki6ITIKr0kceQ6zJUk6oa4zbe5WHvSATXHIE326BHOr 71GQ== X-Gm-Message-State: AOAM530YTlOmDr8eqZSbplJSgClLOgAfWWs+aH8fTi1GL0cRle87jB4A BNRxqRCMm2a3VKkADvos0tEGTw== X-Google-Smtp-Source: ABdhPJy9lkysaX6uIzX9aRvWTgjJ2W3zscEaTyTh7ZhN2JIKeZatk5xdX1wXoAakfOvJhMe4iSWPqw== X-Received: by 2002:a05:6808:6c8:: with SMTP id m8mr5476943oih.142.1599966778559; Sat, 12 Sep 2020 20:12:58 -0700 (PDT) Received: from yoga ([2605:6000:e5cb:c100:8898:14ff:fe6d:34e]) by smtp.gmail.com with ESMTPSA id r132sm1194576oif.24.2020.09.12.20.12.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Sep 2020 20:12:57 -0700 (PDT) Date: Sat, 12 Sep 2020 22:12:55 -0500 From: Bjorn Andersson To: Doug Anderson Cc: Mark Brown , Akash Asthana , Stephen Boyd , Andy Gross , linux-arm-msm , LKML , linux-spi Subject: Re: [PATCH 1/3] spi: spi-geni-qcom: Use the FIFO even more Message-ID: <20200913031255.GR3715@yoga> References: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid> <20200912225302.GA3715@yoga> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 12 Sep 20:11 CDT 2020, Doug Anderson wrote: > Hi, > > On Sat, Sep 12, 2020 at 3:53 PM Bjorn Andersson > wrote: > > > > 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? > > Yeah, I had that worry too, but, as described in 902481a78ee4 ("spi: > spi-geni-qcom: Actually use our FIFO"), it doesn't seem to be a > problem. From that commit: "We are the SPI master, so it makes sense > that there would be no problems with overruns, the master should just > stop clocking." > Actually read the message of the linked commit now. I share your view that this indicates that the controller does something wrt the clocking to handle this case. Change itself looks good, so: Reviewed-by: Bjorn Andersson Regards, Bjorn