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 09340C4332F for ; Mon, 28 Mar 2022 12:45:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242618AbiC1Mrg (ORCPT ); Mon, 28 Mar 2022 08:47:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237500AbiC1Mre (ORCPT ); Mon, 28 Mar 2022 08:47:34 -0400 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5273E4D638; Mon, 28 Mar 2022 05:45:53 -0700 (PDT) Received: by mail-ed1-x529.google.com with SMTP id u26so16736479eda.12; Mon, 28 Mar 2022 05:45:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5GzAXCiHKn740WB88VYaXEioW9TMP9IG2kbGPT2sCHE=; b=FM8dC5tQYBxg/a9sOblYTVnlbCPwqFdeyQ5ziyOF1PY3H389hZlkzBLbqqy8MwXXAf A+dJ+5NOCrBZejlUxbBgQKMOG76kY43DIhH7GNulNDyEM2BWJCrTyjf/fCrvdVV4zNUA 0xUtrt5k4+5+zra4dHdxU7U0iCMWR13OIruhPGOnrjXswbQFT97Fqp5PP3oZUw7el4Mg Sajnpa+xlRqcHYjW/IFTWvlC0Y1LNc38/xUHs6XEG17/JhozHq+3IF3NrsdcdOvrF8mj mU/J6sIX1KmyXwzXQrdyPTsx+QbZuik7yZiPsB4vGQeO4Wd/DsLQJ/Xp1Aj4bp1m3KYj 4+4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5GzAXCiHKn740WB88VYaXEioW9TMP9IG2kbGPT2sCHE=; b=Rws3CDUSt6cqfSqau94G/bKM2rCWbapsoLdf2yBrhIL4gVPXhat6RUjaOBQBC8uJMf SgBNFJ5FMThUPhFFXo3II/Zf/phGfJ3m8XuPV2DjwSRk/Yrly/2Sa1fM9x480muRl9xQ 4IWWog/r5M+JQLp+LrV7ZCzBHUPzUhNA0x4tg8B7FeIMdWfIrTfjN3As3NCyiwiCBv/x 1Q1fPbMzxCO6e2mVUJn0k+eVXZ6NEgVMXbKr3adjN4g3hMqZbIdOsLoza4Leij7WVxV3 cpDcZYmDFED6BtYwozVkJs+SFrbgGXlSYGgYg6/+jnLGwJqD2t85pQuxKiCvgRgyAznx 9o5g== X-Gm-Message-State: AOAM532NtK8rFw8Cr+ikqrrTO3AzklaYUODPurlc/5oI94qdbfZFUjtu UPB3xg6HY2jdh+vjs8OlfvxMdPOHTnWBPyvVpfs= X-Google-Smtp-Source: ABdhPJz90iB17mVjeopA5CGT2QyLyR4w0yF6S9hmFgwrdk/BNJza7oZqY0QP8HkpjT6efjW64Ha/d+eWXtCw8wKKMHY= X-Received: by 2002:aa7:c64c:0:b0:418:ecf7:afaa with SMTP id z12-20020aa7c64c000000b00418ecf7afaamr16277961edr.38.1648471551479; Mon, 28 Mar 2022 05:45:51 -0700 (PDT) MIME-Version: 1.0 References: <20220327123835.28329-1-aford173@gmail.com> <20220327123835.28329-3-aford173@gmail.com> <74e74ea8-1554-bf08-b0ea-36e77259cb18@pengutronix.de> <5c24c12b-3a12-1e18-9f03-2c54cad30bf9@kernel.org> In-Reply-To: <5c24c12b-3a12-1e18-9f03-2c54cad30bf9@kernel.org> From: Adam Ford Date: Mon, 28 Mar 2022 07:45:40 -0500 Message-ID: Subject: Re: [PATCH 3/5] arm64: dts: imx8mp: Enable HS400-ES To: Krzysztof Kozlowski Cc: Ahmad Fatoum , Krzysztof Kozlowski , linux-mmc , devicetree , Ulf Hansson , Fabio Estevam , Shawn Guo , Sascha Hauer , Adam Ford-BE , Haibo Chen , Linux Kernel Mailing List , Rob Herring , NXP Linux Team , Pengutronix Kernel Team , arm-soc Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 28, 2022 at 6:49 AM Krzysztof Kozlowski wrote: > > On 28/03/2022 13:09, Ahmad Fatoum wrote: > > Hello Adam, > > > > On 28.03.22 12:47, Adam Ford wrote: > >> On Mon, Mar 28, 2022 at 2:20 AM Ahmad Fatoum wrote: > >>> > >>> Hello Adam, > >>> > >>> On 27.03.22 14:38, Adam Ford wrote: > >>>> The SDHC controller in the imx8mp has the same controller > >>>> as the imx8mm which supports HS400-ES. Change the compatible > >>>> fallback to imx8mm to enable it. > >>> > >>> I believe that's a shortcoming of the Linux driver, which should explicitly list > >>> fsl,imx8mp-usdhc in its compatibles and enable HS400-ES for it. > >>> > >>> I find dropping compatibles problematic, because like Linux matching > >>> fsl,imx8mm-usdhc, but not fsl,imx8mp-usdhc, other software may match > >>> fsl,imx7d-usdhc, but not fsl,imx8[mp]-usdhc. > >>> > >>> I'd prefer that either the kernel driver gains extra compatibles or that > >>> the DTS lists extra compatibles and we refrain from dropping existing > >>> (correct) ones. > >>> > >> > >> I would argue that imx7d is not correct since the IP blocks between > >> imx7d and imx8mm have different flags/quirks. One of which includes > >> HS400-ES, but there are other differences as well. > > > > The DTS currently says that an fsl,imx7d-usdhc is a subset of an > > fsl,imx8mm-usdhc. So a driver could treat both HW the exact same > > by focusing on the i.MX7D parts. Linux apparently did exactly > > that so far. Is this not accurate? > > > > > >>> What do you think? > >> > >> From my understanding of the fallback compatibility strings is to > >> avoid having to add more and more compatible strings to the drivers > >> when they do not serve a functional purpose. Based On a conversation > >> with Krzysztof [1], he suggested we update the YAML file based on the > >> fallback, but he wanted NXP to give their feedback as to what the > >> right fallback strings should be. Haibo from NXP sent me a hierarchy > >> [1] which is what I used to update the YAML file. Based on the YAML > >> file, the fallback in each DTSI file was updated to ensure the use of > >> the proper IP block. > > > > Myself I am in favor of moving to three compatibles instead of dropping one. > > For some theoretical fsl,imx8mf-usdhc that's supposed to be exactly the same > > as a fsl,imx8mm-usdhc, I don't mind omitting the fsl,imx7d-usdhc compatible, > > but for existing device trees, this may introduce needless potential breakage > > for other software that also uses Linux device trees. > > > > Affecting existing users is indeed a concern with this approach, because > in-kernel DTS might be used in other projects as well. > > I still cannot find here the answer whether fsl,imx8mm-usdhc is actually > compatible with fsl,imx7d-usdhc. It's not about driver, but about > hardware and programming model. imx8mm can support additional features > and still be compatible with imx7d. However if any flags of imx7d are > actually not valid for imx8mm, then it's different case. The imx7d flags are: ESDHC_FLAG_USDHC ESDHC_FLAG_STD_TUNING ESDHC_FLAG_HAVE_CAP1 ESDHC_FLAG_HS200 ESDHC_FLAG_HS400 ESDHC_FLAG_STATE_LOST_IN_LPMODE ESDHC_FLAG_BROKEN_AUTO_CMD23, The imx8mm flags are: ESDHC_FLAG_USDHC ESDHC_FLAG_STD_TUNING ESDHC_FLAG_HAVE_CAP1 ESDHC_FLAG_HS200 ESDHC_FLAG_HS400 ESDHC_FLAG_HS400_ES ESDHC_FLAG_STATE_LOST_IN_LPMODE It does not have the ESDHC_FLAG_BROKEN_AUTO_CMD23 that is present in the imx7d. Maybe Haibo can comment on whether or not that would be an issue for the 8m[mnp] I will defer to Krzysztof and Haibo as to the proper method that we should add HS400-ES. I don't have an issue adding the imx8mn or imx8mp compatible flags to the esdhc driver if that's the decision. If that is the decision, my follow-up question would be how the YAML should look, and if it needs to change at all. adam > > > Best regards, > Krzysztof