From patchwork Mon Apr 20 08:04:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Marek_Beh=C3=BAn?= X-Patchwork-Id: 11498363 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 76B106CA for ; Mon, 20 Apr 2020 08:05:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E30321927 for ; Mon, 20 Apr 2020 08:05:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=nic.cz header.i=@nic.cz header.b="LvdTCkb1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726465AbgDTIE4 (ORCPT ); Mon, 20 Apr 2020 04:04:56 -0400 Received: from mail.nic.cz ([217.31.204.67]:42802 "EHLO mail.nic.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726423AbgDTIEt (ORCPT ); Mon, 20 Apr 2020 04:04:49 -0400 Received: from dellmb.labs.office.nic.cz (unknown [IPv6:2001:1488:fffe:6:cac7:3539:7f1f:463]) by mail.nic.cz (Postfix) with ESMTP id DEB03140E7B; Mon, 20 Apr 2020 10:04:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=nic.cz; s=default; t=1587369885; bh=C+nd6WwPejsTEe2nk+2tSDaddFim/E6HKFWM7ee3e94=; h=From:To:Date; b=LvdTCkb1ktVrq0v/JoSwwKasnh2DmXJ3cRvpWidxLqTN/E6XLcOdUOLo8Z6Bv72aG Kqdyyji8xR3Rn7iK09Eyisz+CJ+jv/+J+wxDr/AA64DbqfnWznrXikSwc8YVZDBpis HAlGbU9tOoRT1rUhDqR73EKA6VxN7mpZIAS4jt1I= From: =?utf-8?q?Marek_Beh=C3=BAn?= To: linux-mmc@vger.kernel.org Cc: =?utf-8?q?Marek_Beh=C3=BAn?= , Zhoujie Wu , Ulf Hansson , Gregory CLEMENT , Vladimir Oltean , Konstantin Porotchkin , Tomasz Maciej Nowak , Miquel Raynal Subject: [PATCH v2] mmc: sdhci-xenon: fix annoying 1.8V regulator warning Date: Mon, 20 Apr 2020 10:04:44 +0200 Message-Id: <20200420080444.25242-1-marek.behun@nic.cz> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on mail.nic.cz X-Spam-Status: No, score=0.00 X-Spamd-Bar: / X-Virus-Scanned: clamav-milter 0.101.4 at mail X-Virus-Status: Clean Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org For some reason the Host Control2 register of the Xenon SDHCI controller sometimes reports the bit representing 1.8V signaling as 0 when read after it was written as 1. Subsequent read reports 1. This causes the sdhci_start_signal_voltage_switch function to report 1.8V regulator output did not become stable When CONFIG_PM is enabled, the host is suspended and resumend many times, and in each resume the switch to 1.8V is called, and so the kernel log reports this message annoyingly often. Do an empty read of the Host Control2 register in Xenon's .voltage_switch method to circumvent this. This patch fixes this particular problem on Turris MOX. Signed-off-by: Marek Behún Fixes: 8d876bf472db ("mmc: sdhci-xenon: wait 5ms after set 1.8V...") Cc: Zhoujie Wu Cc: Ulf Hansson Cc: Gregory CLEMENT Cc: Vladimir Oltean Cc: Konstantin Porotchkin Cc: Tomasz Maciej Nowak Cc: Miquel Raynal --- drivers/mmc/host/sdhci-xenon.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c index 1dea1ba66f7b..4703cd540c7f 100644 --- a/drivers/mmc/host/sdhci-xenon.c +++ b/drivers/mmc/host/sdhci-xenon.c @@ -235,6 +235,16 @@ static void xenon_voltage_switch(struct sdhci_host *host) { /* Wait for 5ms after set 1.8V signal enable bit */ usleep_range(5000, 5500); + + /* + * For some reason the controller's Host Control2 register reports + * the bit representing 1.8V signaling as 0 when read after it was + * written as 1. Subsequent read reports 1. + * + * Since this may cause some issues, do an empty read of the Host + * Control2 register here to circumvent this. + */ + sdhci_readw(host, SDHCI_HOST_CONTROL2); } static const struct sdhci_ops sdhci_xenon_ops = {