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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 7A322C55181 for ; Tue, 21 Apr 2020 09:26:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56D5F20857 for ; Tue, 21 Apr 2020 09:26:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="i44fOYZU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728495AbgDUJ0M (ORCPT ); Tue, 21 Apr 2020 05:26:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728123AbgDUJ0K (ORCPT ); Tue, 21 Apr 2020 05:26:10 -0400 Received: from mail-vk1-xa41.google.com (mail-vk1-xa41.google.com [IPv6:2607:f8b0:4864:20::a41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B6588C061A10 for ; Tue, 21 Apr 2020 02:26:10 -0700 (PDT) Received: by mail-vk1-xa41.google.com with SMTP id p123so3419890vkg.1 for ; Tue, 21 Apr 2020 02:26:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sutV1Oamoy4pwRt+VwqP9AtJQW6IanilRtSt3lz61TU=; b=i44fOYZUDMFqxzO+bLxz7mYEXUJOrpBd6UGd2O+okyMUpCDdFKYIA826sUc7iPf6we js7pHNoTwz0e4R+VDEEez61/nomAfRCsuE94AcZJ9S5rehCXy1mKu/shAWtzpt5XfI+r l2r9o/esXgf9BSBCXfnnvw6hbSFBgzLYaI5HilgMBU9YGUTsg5p6E8mn0f/ULpHUceV+ grZbBZ4lBL1a3TWwDjxTT1wtbs2ryIpbqkXG4MOXWlfVjB0C5532Ob0xNjO+leG/B2jP C7PZF9bGVE3w+BOpv+3h7rP7Iv2Zp5h7xvJNVCEBTX3s7LvKyKbqlZBsoksAMNcbHIKb 3+cg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sutV1Oamoy4pwRt+VwqP9AtJQW6IanilRtSt3lz61TU=; b=SDNmXjeqqIyyDcNXmK8CSpQ5V9gCABayTJS3omU34RyB1Y7f5/Vkq6IXI8mPOz0Rvf z/Knsau8OlIfzMcsuNg0+e5L0Tjmzs/CQ95V84eTliG1TBiSw3B4VF2J5weKLMCpFsFt vL+AwIFB7cqQ5ixnaMV1WdAMtCsUYjPriZbvPsY60tsLQ+8fPydiRJ/NcOG6il3NYp5b Jip+bSyFs3JFALQU2j9ms50KZhANZfsuK+IwG+P4Brfj74hQCrnARX0basgGuJOrEo9O 1sdFODPOmxlP2CygDkvsYk+nILPXiMpdY7cLssCRZK52yoYXROpJ7UpWMgq3aW0XDOSx LllA== X-Gm-Message-State: AGi0PuZvk98Y4+JmzT+cv6Uyg0lzlbCDYfSmsrh8Bvql8GcGqCfB/n8x g6SOuoHNUHsDfnDH1zQVSPg/S8LkE9jZiiYJx0nscQ== X-Google-Smtp-Source: APiQypKgJ3XD4p50nn/CNLH8KAToU17AAWt5xtoXI0IXMljJSdFyItYyZUEcdUyWP2PTkh+mgDLx1kzXR3Z25Pm/P1U= X-Received: by 2002:a1f:a60b:: with SMTP id p11mr8434277vke.43.1587461169800; Tue, 21 Apr 2020 02:26:09 -0700 (PDT) MIME-Version: 1.0 References: <20200420161831.5043-1-ludovic.barre@st.com> In-Reply-To: <20200420161831.5043-1-ludovic.barre@st.com> From: Ulf Hansson Date: Tue, 21 Apr 2020 11:25:33 +0200 Message-ID: Subject: Re: [PATCH] mmc: mmci_sdmmc: fix power on issue due to pwr_reg initialization To: Ludovic Barre Cc: Rob Herring , Srini Kandagatla , Maxime Coquelin , Alexandre Torgue , Linux ARM , Linux Kernel Mailing List , DTML , "linux-mmc@vger.kernel.org" , linux-stm32@st-md-mailman.stormreply.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 20 Apr 2020 at 18:18, Ludovic Barre wrote: > > This patch fix a power-on issue, and avoid to retry the power sequence. > > In power off sequence: sdmmc must set pwr_reg in "power-cycle" state > (value 0x2), to prevent the card from being supplied through the signal > lines (all the lines are driven low). > > In power on sequence: when the power is stable, sdmmc must set pwr_reg > in "power-off" state (value 0x0) to drive all signal to high before to > set "power-on". Just a question to gain further understanding. Let's assume that the controller is a power-on state, because it's been initialized by the boot loader. When the mmc core then starts the power-on sequence (not doing a power-off first), would $subject patch then cause the MMCIPOWER to remain as is, or is it going to be overwritten? I am a little worried that we may start to rely on boot loader conditions, which isn't really what we want either... > > To avoid writing the same value to the power register several times, this > register is cached by the pwr_reg variable. At probe pwr_reg is initialized > to 0 by kzalloc of mmc_alloc_host. > > Like pwr_reg value is 0 at probing, the power on sequence fail because > the "power-off" state is not writes (value 0x0) and the lines > remain drive to low. > > This patch initializes "pwr_reg" variable with power register value. > This it done in sdmmc variant init to not disturb default mmci behavior. > > Signed-off-by: Ludovic Barre Besides the comment, the code and the approach seems reasonable to me. Kind regards Uffe > --- > > This patch is the proposal from: > https://patchwork.kernel.org/patch/11457987/ > > --- > drivers/mmc/host/mmci_stm32_sdmmc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c > index d33e62bd6153..14f99d8aa3f0 100644 > --- a/drivers/mmc/host/mmci_stm32_sdmmc.c > +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c > @@ -519,6 +519,7 @@ void sdmmc_variant_init(struct mmci_host *host) > struct sdmmc_dlyb *dlyb; > > host->ops = &sdmmc_variant_ops; > + host->pwr_reg = readl_relaxed(host->base + MMCIPOWER); > > base_dlyb = devm_of_iomap(mmc_dev(host->mmc), np, 1, NULL); > if (IS_ERR(base_dlyb)) > -- > 2.17.1 >