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 phobos.denx.de (phobos.denx.de [85.214.62.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A2E16C25B76 for ; Mon, 3 Jun 2024 12:27:49 +0000 (UTC) Received: from h2850616.stratoserver.net (localhost [IPv6:::1]) by phobos.denx.de (Postfix) with ESMTP id 2469B882AC; Mon, 3 Jun 2024 14:27:48 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=u-boot-bounces@lists.denx.de Received: by phobos.denx.de (Postfix, from userid 109) id 3AF0087FF0; Mon, 3 Jun 2024 10:18:45 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by phobos.denx.de (Postfix) with ESMTP id 202CC874D4 for ; Mon, 3 Jun 2024 10:18:43 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=christian.loehle@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A87741042; Mon, 3 Jun 2024 01:19:06 -0700 (PDT) Received: from [10.57.83.47] (unknown [10.57.83.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EAD0E3F792; Mon, 3 Jun 2024 01:18:40 -0700 (PDT) Message-ID: Date: Mon, 3 Jun 2024 09:18:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: obscure microsd detection issue between U-Boot and kernel To: Tim Harvey , u-boot , Peng Fan , Jaehoon Chung , Linux MMC List , Ulf Hansson References: Content-Language: en-US From: Christian Loehle In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Mon, 03 Jun 2024 14:27:46 +0200 X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.8 at phobos.denx.de X-Virus-Status: Clean On 5/31/24 21:47, Tim Harvey wrote: > Greetings, > > I'm seeing an issue on an imx8mm board (imx8mm-venice-gw73xx) where > for a specific set of microsd cards if I have accessed the microsd in > U-Boot with UHS/1.8V the kernel will not recognize that microsd when > scanning. > > The issue does not occur with all microsd cards but seems to appear > with a large sample size of a specific card/model (Kingston SDC32 32GB > SDR104 card). I do not see a signal integrity issue on the scope. > > Instrumenting the kernel the issue is that the host reports a CRC > error as soon as the first mmc_send_if_cond call which occurs in > mmc_rescan_try_freq. > > I can avoid the issue by either not accessing the microsd in U-Boot or > by disabling UHS/1.8V mode in U-Boot therefore what I think is > happening is that U-Boot leaves the card in UHS/1.8V signalling mode > and when the kernel scans it sets the voltage back to 3.3V > standard/default and default timings then issues its clock cycles to > 'reset' the card and the card does not recognize the reset. I'm > wondering if this is because the reset is done via clock cycles after > the kernel has set the I/O voltage back to 3.3V when perhaps the card > is still in 1.8V mode (although I don't see how that would cause an > issue)? It will cause an issue for many cards and might break some cards. > > Is there some sort of MMC 'reset' I can/should do in U-Boot before > booting the kernel? Has anyone encountered anything like this before? There is no 'switching back' to 3.3V signalling from UHS 1.8V. The only way this can be done is therefore a full power-off. Is that done correctly for your system? AFAIR spec dictates 500ms of <0.5V on VCC. Note that driving CLK/signal lines can also sustain the card somewhat, as leakage is only limited within operating voltage.