From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EA33A21B199; Mon, 18 Aug 2025 13:05:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755522305; cv=none; b=CxDDR3nuXFksq6W3JXPiSfP5lxLkN6iNpHhseUVXVxEVM2Q5RfAk8q19edl1jSr9CeBdgG6uOtyEPdII01e5aqA0btwhbp59S0p1w5QkCNAIALfM6HAcrwO6Y0Uu7QQWZIF7zicFy/CTu5qB4SxZVG3Q62/3f5zRCKod9OCJywU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755522305; c=relaxed/simple; bh=F7P4ATjyhRLkOeywqHJ2ZmS1Fap35vx4MA5uu8cSf0Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HwUv/uwiwtf2tyoavorZp8WFl4QVWuiKtJsGBlMt9onMv/AnfW3UVWJWuszDinBmEmzJu9H/DOKqzmWPq3irtEynAAcNjRNFx7mug6+BdpbB+eRvlh1j0uTWwJWicX51xDekguFOnfvLi7Is5H35+TPyoGfyLgNbTPK/zaf8qOE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1FnHYHSl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1FnHYHSl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF1DFC4CEEB; Mon, 18 Aug 2025 13:05:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755522304; bh=F7P4ATjyhRLkOeywqHJ2ZmS1Fap35vx4MA5uu8cSf0Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1FnHYHSlJGBwQ9aBuCT9zGyzIoSHH6yAeVHjHnE+Csbhzcjl2/3IXKGYsdjoDSWo9 /waXKDIrPnfLCBYUtZRbjQbsPM0Iz0Ny8if39qe5BUg5+kbTra71cfqNU4NirszJqO AACeP81vHPJhY+9gMINg0zXHq1qlqyjTihoFRpAE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Aaron Plattner , Timur Tabi , Guenter Roeck , Wim Van Sebroeck , Sasha Levin Subject: [PATCH 6.12 276/444] watchdog: sbsa: Adjust keepalive timeout to avoid MediaTek WS0 race condition Date: Mon, 18 Aug 2025 14:45:02 +0200 Message-ID: <20250818124459.320563589@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124448.879659024@linuxfoundation.org> References: <20250818124448.879659024@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aaron Plattner [ Upstream commit 48defdf6b083f74a44e1f742db284960d3444aec ] The MediaTek implementation of the sbsa_gwdt watchdog has a race condition where a write to SBSA_GWDT_WRR is ignored if it occurs while the hardware is processing a timeout refresh that asserts WS0. Detect this based on the hardware implementer and adjust wdd->min_hw_heartbeat_ms to avoid the race by forcing the keepalive ping to be one second later. Signed-off-by: Aaron Plattner Acked-by: Timur Tabi Reviewed-by: Guenter Roeck Link: https://lore.kernel.org/r/20250721230640.2244915-1-aplattner@nvidia.com Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck Signed-off-by: Sasha Levin --- drivers/watchdog/sbsa_gwdt.c | 50 +++++++++++++++++++++++++++++++++--- 1 file changed, 47 insertions(+), 3 deletions(-) diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c index 5f23913ce3b4..6ce1bfb39064 100644 --- a/drivers/watchdog/sbsa_gwdt.c +++ b/drivers/watchdog/sbsa_gwdt.c @@ -75,11 +75,17 @@ #define SBSA_GWDT_VERSION_MASK 0xF #define SBSA_GWDT_VERSION_SHIFT 16 +#define SBSA_GWDT_IMPL_MASK 0x7FF +#define SBSA_GWDT_IMPL_SHIFT 0 +#define SBSA_GWDT_IMPL_MEDIATEK 0x426 + /** * struct sbsa_gwdt - Internal representation of the SBSA GWDT * @wdd: kernel watchdog_device structure * @clk: store the System Counter clock frequency, in Hz. * @version: store the architecture version + * @need_ws0_race_workaround: + * indicate whether to adjust wdd->timeout to avoid a race with WS0 * @refresh_base: Virtual address of the watchdog refresh frame * @control_base: Virtual address of the watchdog control frame */ @@ -87,6 +93,7 @@ struct sbsa_gwdt { struct watchdog_device wdd; u32 clk; int version; + bool need_ws0_race_workaround; void __iomem *refresh_base; void __iomem *control_base; }; @@ -161,6 +168,31 @@ static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd, */ sbsa_gwdt_reg_write(((u64)gwdt->clk / 2) * timeout, gwdt); + /* + * Some watchdog hardware has a race condition where it will ignore + * sbsa_gwdt_keepalive() if it is called at the exact moment that a + * timeout occurs and WS0 is being asserted. Unfortunately, the default + * behavior of the watchdog core is very likely to trigger this race + * when action=0 because it programs WOR to be half of the desired + * timeout, and watchdog_next_keepalive() chooses the exact same time to + * send keepalive pings. + * + * This triggers a race where sbsa_gwdt_keepalive() can be called right + * as WS0 is being asserted, and affected hardware will ignore that + * write and continue to assert WS0. After another (timeout / 2) + * seconds, the same race happens again. If the driver wins then the + * explicit refresh will reset WS0 to false but if the hardware wins, + * then WS1 is asserted and the system resets. + * + * Avoid the problem by scheduling keepalive heartbeats one second later + * than the WOR timeout. + * + * This workaround might not be needed in a future revision of the + * hardware. + */ + if (gwdt->need_ws0_race_workaround) + wdd->min_hw_heartbeat_ms = timeout * 500 + 1000; + return 0; } @@ -202,12 +234,15 @@ static int sbsa_gwdt_keepalive(struct watchdog_device *wdd) static void sbsa_gwdt_get_version(struct watchdog_device *wdd) { struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd); - int ver; + int iidr, ver, impl; - ver = readl(gwdt->control_base + SBSA_GWDT_W_IIDR); - ver = (ver >> SBSA_GWDT_VERSION_SHIFT) & SBSA_GWDT_VERSION_MASK; + iidr = readl(gwdt->control_base + SBSA_GWDT_W_IIDR); + ver = (iidr >> SBSA_GWDT_VERSION_SHIFT) & SBSA_GWDT_VERSION_MASK; + impl = (iidr >> SBSA_GWDT_IMPL_SHIFT) & SBSA_GWDT_IMPL_MASK; gwdt->version = ver; + gwdt->need_ws0_race_workaround = + !action && (impl == SBSA_GWDT_IMPL_MEDIATEK); } static int sbsa_gwdt_start(struct watchdog_device *wdd) @@ -299,6 +334,15 @@ static int sbsa_gwdt_probe(struct platform_device *pdev) else wdd->max_hw_heartbeat_ms = GENMASK_ULL(47, 0) / gwdt->clk * 1000; + if (gwdt->need_ws0_race_workaround) { + /* + * A timeout of 3 seconds means that WOR will be set to 1.5 + * seconds and the heartbeat will be scheduled every 2.5 + * seconds. + */ + wdd->min_timeout = 3; + } + status = readl(cf_base + SBSA_GWDT_WCS); if (status & SBSA_GWDT_WCS_WS1) { dev_warn(dev, "System reset by WDT.\n"); -- 2.39.5