From patchwork Sun May 21 12:19:40 2023 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: 684806 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 60631C7EE23 for ; Sun, 21 May 2023 12:19:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230037AbjEUMTy (ORCPT ); Sun, 21 May 2023 08:19:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbjEUMTx (ORCPT ); Sun, 21 May 2023 08:19:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 250C5AA for ; Sun, 21 May 2023 05:19:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AF1A360C25 for ; Sun, 21 May 2023 12:19:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33F57C433EF; Sun, 21 May 2023 12:19:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684671591; bh=tfRnbBUuVALsCjtyyYhE9Q63qD8wS1OT5P92jV/IUEY=; h=From:To:Cc:Subject:Date:From; b=e6N9x002lnf92jodcMxqj2c9nZsu4AcYiDEF/hJ9W9h8zlxWKv4FIvISFggb+OkOt qcliML2+xoHwKTYhoF4ER+eJpms8/p6PcWtat7LEkA96VrExdXwUjZTABTtuAWxh2h NfzcE/y3+0oKLSC1fQYQlnR9mxzGU0m3+L2hfi5cgH7xi2kAVHe+j8jkrIMqDvolIM 5HIckRnbH01WR/hat4PSV/5hK2H15fJvuj62nrNwJL58iOQ1feJh9t4aQ6RAzilQIK fEdb9JP8e8MN3+nvkfAfEiwOdRLR/udKaARoLlY9w/B3tE2QCvILeN+WuYs4Dm1c+V CZyQ/48bZkhwA== From: =?utf-8?q?Marek_Beh=C3=BAn?= To: linux-i2c@vger.kernel.org, Wolfram Sang , Gregory CLEMENT Cc: Samuel Holland , Chris Morgan , Russell King , =?utf-8?q?Marek_Beh=C3=BAn?= Subject: [PATCH] i2c: mv64xxx: Fix reading invalid status value in atomic mode Date: Sun, 21 May 2023 14:19:40 +0200 Message-Id: <20230521121940.27057-1-kabel@kernel.org> X-Mailer: git-send-email 2.39.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org There seems to be a bug within the mv64xxx I2C controller, wherein the status register may not necessarily contain valid value immediately after the IFLG flag is set in the control register. My theory is that the controller: - first sets the IFLG in control register - then updates the status register - then raises an interrupt This may sometime cause weird bugs when in atomic mode, since in this mode we do not wait for an interrupt, but instead we poll the control register for IFLG and read status register immediately after. I encountered -ENXIO from mv64xxx_i2c_fsm() due to this issue when using this driver in atomic mode. Note that I've only seen this issue on Armada 385, I don't know whether other SOCs with this controller are also affected. Also note that this fix has been in U-Boot for over 4 years [1] without anybody complaining, so it should not cause regressions. [1] https://source.denx.de/u-boot/u-boot/-/commit/d50e29662f78 Fixes: 544a8d75f3d6 ("i2c: mv64xxx: Add atomic_xfer method to driver") Signed-off-by: Marek Behún --- drivers/i2c/busses/i2c-mv64xxx.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c index 047dfef7a657..878c076ebdc6 100644 --- a/drivers/i2c/busses/i2c-mv64xxx.c +++ b/drivers/i2c/busses/i2c-mv64xxx.c @@ -520,6 +520,17 @@ mv64xxx_i2c_intr(int irq, void *dev_id) while (readl(drv_data->reg_base + drv_data->reg_offsets.control) & MV64XXX_I2C_REG_CONTROL_IFLG) { + /* + * It seems that sometime the controller updates the status + * register only after it asserts IFLG in control register. + * This may result in weird bugs when in atomic mode. A delay + * of 100 ns before reading the status register solves this + * issue. This bug does not seem to appear when using + * interrupts. + */ + if (drv_data->atomic) + ndelay(100); + status = readl(drv_data->reg_base + drv_data->reg_offsets.status); mv64xxx_i2c_fsm(drv_data, status); mv64xxx_i2c_do_action(drv_data);