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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AE440C433EF for ; Mon, 28 Mar 2022 13:14:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=SARcX3q6tBsLlWzW1s73rZ5CegrZlIPzhUEvDg7pasw=; b=onnGlzIjoxg2y0 lr5+c0KCo9WGmkAyJkRwkYEm6Qj2On/mkWxNt8Dy8xA5u3nmG3LrUKUQ+5wdEHpeb0jdARVxZNlhi NrrXryjfnxaEdpXfu5ggDOJKVMakjrQv+l+Tnl3zDrbXXk+XKk4Nv89yflxbyMF+rXhl7FmhxBIfR Vokv2euUVbyQKr3zQPOgDOtIjUULKpu7clJKUCjQ5MTYrAJvMH/rsZn3EQFh+3tM18AiX8EjzQl8U pgLHL6K1+IA02uUH+1nlrlD3vWlvJGgBWhH5SfWjlHcJufCiHRMO1HbMrxSb7ni63k4ohvx2g3TBc aMXPte3o5G8giXePAOYg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nYpBQ-008guI-3W; Mon, 28 Mar 2022 13:13:21 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nYpB5-008giY-1b for linux-arm-kernel@lists.infradead.org; Mon, 28 Mar 2022 13:13:01 +0000 Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=[127.0.0.1]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1nYpAj-0001It-C4; Mon, 28 Mar 2022 15:12:37 +0200 Message-ID: <6c11c94e-6a3f-323b-37fe-e1b47da106ac@pengutronix.de> Date: Mon, 28 Mar 2022 15:12:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 3/5] arm64: dts: imx8mp: Enable HS400-ES Content-Language: en-US To: Adam Ford , Krzysztof Kozlowski Cc: 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 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> <5282b39b-85d5-81d6-10d5-a45c66d4d4e9@kernel.org> From: Ahmad Fatoum In-Reply-To: X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: a.fatoum@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220328_061259_275333_A69E4E25 X-CRM114-Status: GOOD ( 39.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Adam, On 28.03.22 15:06, Adam Ford wrote: > On Mon, Mar 28, 2022 at 7:56 AM Krzysztof Kozlowski wrote: >> >> On 28/03/2022 14:45, Adam Ford wrote: >>> 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. >> >> AFAIU, it looks imx8mm is compatible with imx7d, because the broken >> acmd23 only limits the features. If imx8mm binds according to imx7d, it >> will not support acmd23 and HS400-ES. >> >> Having three compatibles is therefore also OK. >> >> You could also add two cases: >> 1. three compatibles, deprecated: True, >> 2. two compatibles, without imx7d. >> >> Existing DTS stays with three compatibles for two years and later gets >> converted to two compatibles. New DTS should use two compatibles. >> >> It's quite a lot of churn, but would make in the long term bindings >> correct and also not break other users/projects. >> >>> >>> 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. >> >> I don't get what's the problem with HS400-ES. In any case (your patch >> here, other ideas) your DTS will bind to imx8mm-usdhc which has HS400-ES. > > I was under the impression Ahmad didn't want me to add the imx8mm > compatible to the DTS, but instead, add the imx8mp compatible into the > driver so it binds directly to an imx8mp. > Based on that, I was assuming this patch series would be rejected and > I sould focus on just the driver file itself My objection is about dropping the compatible. I am fine with either: - adding fsl,imx8mm-usdhc as an additional compatible - extending the Linux driver I am myself unsure, which is the preferred way, but both resolve your issue, while not breaking other so far valid uses. Cheers, Ahmad > From what I am reading from you, I should make the imx8mn and imx8mp > device trees respectively read: > > compatible = "fsl,imx8mn-usdhc", "fsl,imx8mm-usdhc", "fsl,imx7d-usdhc"; > > and > > compatible = "fsl,imx8mp-usdhc", "fsl,imx8mm-usdhc", "fsl,imx7d-usdhc"; > > If that's true, do I need to change the YAML at all? > > adam >> >> Best regards, >> Krzysztof > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel