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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11590C7EE2E for ; Mon, 12 Jun 2023 10:54:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235900AbjFLKyW (ORCPT ); Mon, 12 Jun 2023 06:54:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235749AbjFLKyI (ORCPT ); Mon, 12 Jun 2023 06:54:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2AD17659C for ; Mon, 12 Jun 2023 03:39:33 -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 BBD77623F9 for ; Mon, 12 Jun 2023 10:39:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D11C7C433EF; Mon, 12 Jun 2023 10:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1686566372; bh=HQR/13KzU5RffhfRFOf5jmVv9AYoWURiRUMrvT0K3HE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zL7rgUsvUWEbGBh2H7G4/WMvGteX9eyBa658maV0W7CCTo82p5G31jVZFb+F50INF SndPAWcRI2yFRXIeaGw02iNAh4nGJ/SIP2iu/tNZEr08y/s8UEUNJyLolOT3ip7dQi MynDz15wC4or4iOPjG00ltrKjFW92ggkAhte2uXQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Marek=20Beh=C3=BAn?= , Wolfram Sang , Sasha Levin Subject: [PATCH 5.15 79/91] i2c: mv64xxx: Fix reading invalid status value in atomic mode Date: Mon, 12 Jun 2023 12:27:08 +0200 Message-ID: <20230612101705.378514509@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230612101702.085813286@linuxfoundation.org> References: <20230612101702.085813286@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Marek Behún [ Upstream commit 5578d0a79b6430fa1543640dd6f2d397d0886ce7 ] 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 Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- 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 103a05ecc3d6b..9729a71b25672 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); -- 2.39.2