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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C0C6C61DB3 for ; Mon, 9 Jan 2023 20:44:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235131AbjAIUoU (ORCPT ); Mon, 9 Jan 2023 15:44:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235473AbjAIUn4 (ORCPT ); Mon, 9 Jan 2023 15:43:56 -0500 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA0974ECB8 for ; Mon, 9 Jan 2023 12:43:55 -0800 (PST) Received: by mail-pl1-x632.google.com with SMTP id s8so2561825plk.5 for ; Mon, 09 Jan 2023 12:43:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=in-reply-to:mime-version:user-agent:date:message-id:from:references :cc:to:subject:from:to:cc:subject:date:message-id:reply-to; bh=EgIp64wR5rCqasADNvQH+AVw8h1xGfwjU6s44y76QJM=; b=UhaZZZ3nFggV2QuaA/bx2AQwDz3tF1zsmJt1+d3wqjlcrUTlnAj0glsHDa04RAYVJM raZAwYhThHhCKWW1c5Dx7FJB2D/SwL0rg6AuWeZeb+C51KzWYdJw/R3OxyLf+74Lk5lM /2FJOocqVibc2f7khaeMQqkEF1+MhCr3U4KA4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:mime-version:user-agent:date:message-id:from:references :cc:to:subject:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=EgIp64wR5rCqasADNvQH+AVw8h1xGfwjU6s44y76QJM=; b=1GJeOGdsQG1WjRv0lYh3sUmqQxTk4eksQ+86VJR5HQwt7SJ5JxVDxQmTrzfyK2EYm6 iyIwq1X97karunzDf1vQE1NhkKB5yMqXuS2wT+GAjDDX2auZPkOA37M15UDqPY6sAjAk la7uQocJ6VT/vf2NlSKJcVjRcMR4Dg6hAhfRqtSXVCtD8yZlytM3jdTeAKZ0JT+QI+Qg pXNlvftNWqvyfY/0qiB0NuRzx7SgOFoEtO0v9yuXUF+JB4VBcltQazI9Hi56EEYq1o6p F8VwnJ5W0xKvH8bh0IeATzb3SK/lKzJNxFga1lEVFu4wYVzia+mt0Cb9gSlaFqzucctK lLNg== X-Gm-Message-State: AFqh2koWDN3K2p7DJnzh8ZGZSQktmb+Rub4+ir2/VyLn/OjC2ySSsu+c YaH2Yu/JTjuMgnMWKqzG3n3HtsUCVUAUFl+Chp6QEGsoPLfkaAU2BLTckQqcQAeBsqJbKC1avIB k3buXZ+P6x4/El9h0GQ9H3ddjcCqwaHSG0CJscUiGi6JfdDFUXc+VAXmSKbaNMOptrdR1Lt8IoS Dy2Uee5DnjWXo= X-Google-Smtp-Source: AMrXdXvws7J1qmSfAhQIhRJk4KTFCG246r2YS9mc7sz4wfRXUaQS4wjyi4fvwDHKglC9cxwUqXTOpA== X-Received: by 2002:a17:902:f70c:b0:188:6b9c:d17d with SMTP id h12-20020a170902f70c00b001886b9cd17dmr86838478plo.16.1673297035026; Mon, 09 Jan 2023 12:43:55 -0800 (PST) Received: from bcacpedev-irv-3.lvn.broadcom.net ([192.19.161.250]) by smtp.gmail.com with ESMTPSA id e2-20020a170902784200b0017d97d13b18sm6566604pln.65.2023.01.09.12.43.53 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 09 Jan 2023 12:43:54 -0800 (PST) Subject: Re: [PATCH 11/16] spi: bcm63xx-hsspi: Add prepend feature support To: Mark Brown Cc: Linux SPI List , Broadcom Kernel List , anand.gore@broadcom.com, tomer.yacoby@broadcom.com, dan.beygelman@broadcom.com, joel.peshkin@broadcom.com, f.fainelli@gmail.com, jonas.gorski@gmail.com, kursad.oney@broadcom.com, dregan@mail.com, linux-kernel@vger.kernel.org References: <20230106200809.330769-1-william.zhang@broadcom.com> <20230106200809.330769-12-william.zhang@broadcom.com> <88534207-6b1c-75c1-26a1-be88a19eeecb@broadcom.com> From: William Zhang Message-ID: <04b740e0-09d1-8c39-4f0e-8f61a74eeb58@broadcom.com> Date: Mon, 9 Jan 2023 12:43:53 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="00000000000067f12205f1dad346" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --00000000000067f12205f1dad346 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit On 01/09/2023 11:31 AM, Mark Brown wrote: > On Fri, Jan 06, 2023 at 07:52:35PM -0800, William Zhang wrote: >> On 01/06/2023 02:00 PM, Mark Brown wrote: >>> On Fri, Jan 06, 2023 at 12:08:03PM -0800, William Zhang wrote: > >>>> Multiple transfers within a SPI message may be combined into one >>>> transfer to the controller using its prepend feature. A SPI message is >>>> prependable only if the following are all true: >>>> * One or more half duplex write transfer >>>> * Optional full duplex read/write at the end >>>> * No delay and cs_change between transfers > >>> There is nothing driver specific here, this should be implemented in the >>> core - we have existing logic to rewrite messages to match driver >>> constraints, this could be added there possibly with flags to allow >>> drivers to disable or enable the merging if they've got special >>> requirements. > >> My understanding of combining the spi transfer in the core level does not >> quite work out to our controller. For example, for a spi message with three >> transfers, tx, tx and rx. We can possibly combine them in single duplex >> tx/rx transfer in the core. But this will be treated as duplex transaction >> in our controller level which require tx and rx data happens at the same >> time. Obviously this won't work when rx depends on tx happening first. We > > I'm saying that if this logic is useful then implement in the core > rather than in the driver. > >> can not differentiate this combined duplex transfer from the true duplex >> transfer unless there is some flag to indicate that. Also there is limit of >> max tx length as the prepend buffer so maybe another parameter. And another >> reason to be done in the driver level is this prepend mode has dependency on >> dummy cs workaround which is driver level parameter currently. I am not >> sure how practical and useful this is to factor them out to the core level? > > If this relies on software control of the chip select (which is what I > *think* your dummy CS workaround thing is about, the other patch about > that is really hard to understand) then I'm confused about what the > advantage is? Dummy CS workaround is implemented by Jonas when he first upstream the driver. It does not work on all the board designs so prepend mode is introduced. I have some detail explanation on this in [PATCH 10/16] spi: bcm63xx-hsspi: Make dummy cs workaround as an option. The controller only work in one mode and that's why driver code has some dependency between these two modes. The advantage of the premode is it works on all hw design however it does not support all types mem_ops operation. That is why you see the patch 14 to disable the dual io mem op. But dummy cs workaround can support this and in case there is such pattern from non mem op spi transaction, dummy cs workaround can be used as long as it does not have the board design limitation. So neither one is perfect but hopefully with both options available, we can cover all the cases. You mentioned there is some existing logic to rewrite messages to match driver constraints in the core driver. I didn't see it when I did a quick search on spi.c. I will take a deep look into the file. But if you can point me where this logic is so I can be sure that I am looking at the right place and will double check if this can be done or not in the core level. Thanks! > --00000000000067f12205f1dad346 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIQcAYJKoZIhvcNAQcCoIIQYTCCEF0CAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg gg3HMIIFDTCCA/WgAwIBAgIQeEqpED+lv77edQixNJMdADANBgkqhkiG9w0BAQsFADBMMSAwHgYD VQQLExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UE AxMKR2xvYmFsU2lnbjAeFw0yMDA5MTYwMDAwMDBaFw0yODA5MTYwMDAwMDBaMFsxCzAJBgNVBAYT AkJFMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMTEwLwYDVQQDEyhHbG9iYWxTaWduIEdDQyBS MyBQZXJzb25hbFNpZ24gMiBDQSAyMDIwMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA vbCmXCcsbZ/a0fRIQMBxp4gJnnyeneFYpEtNydrZZ+GeKSMdHiDgXD1UnRSIudKo+moQ6YlCOu4t rVWO/EiXfYnK7zeop26ry1RpKtogB7/O115zultAz64ydQYLe+a1e/czkALg3sgTcOOcFZTXk38e aqsXsipoX1vsNurqPtnC27TWsA7pk4uKXscFjkeUE8JZu9BDKaswZygxBOPBQBwrA5+20Wxlk6k1 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