From nobody Fri Dec 19 10:11:32 2025 Received: from TWMBX01.aspeed.com (mail.aspeedtech.com [211.20.114.72]) (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 08EA3270EC1; Tue, 9 Dec 2025 11:15:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=211.20.114.72 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765278942; cv=none; b=ub58rc6uT2GpvNQrAbYiJ7FPmEDMgYH+xkDOg7AgABvKjyYGqD2d5/EGkOKNBfjU1opXa6HV3rSeRIx5WXygO39HwlGTW8etaeRZIHxh4n0aZRsMBVHaQgU0+9+uk+j/M3d8YgUyq3O5YmE9ASOjgKANR4ttIWYl3hkRPiDoWP8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765278942; c=relaxed/simple; bh=Mg8PdAkgzIWHVGruAAz0jujfLeSjM7YjkzAbXqHp61U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-ID:To:CC; b=aOL9mXdqTwhhA4KhGUB+8BGa/8xCMyWfuJpLzGdyhhrYum6XaQZ5VJ+q53J8m1+uQ0oWwzKnbzzPWbIhfgWDnjakKfLnGbZL+s9pcK6iEBmKDpffl6UKTD+ydQPgCWHACbQwjwromiNpNIMYy9pG4pO/bePLIkXxHH430yZyqyU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=aspeedtech.com; spf=pass smtp.mailfrom=aspeedtech.com; arc=none smtp.client-ip=211.20.114.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=aspeedtech.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=aspeedtech.com Received: from TWMBX01.aspeed.com (192.168.0.62) by TWMBX01.aspeed.com (192.168.0.62) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1748.10; Tue, 9 Dec 2025 19:15:32 +0800 Received: from [127.0.1.1] (192.168.10.13) by TWMBX01.aspeed.com (192.168.0.62) with Microsoft SMTP Server id 15.2.1748.10 via Frontend Transport; Tue, 9 Dec 2025 19:15:32 +0800 From: Jacky Chou Date: Tue, 9 Dec 2025 19:15:31 +0800 Subject: [PATCH net v2] net: mdio: aspeed: add dummy read to avoid read-after-write issue Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-ID: <20251209-aspeed_mdio_add_dummy_read-v2-1-5f6061641989@aspeedtech.com> X-B4-Tracking: v=1; b=H4sIANIEOGkC/42NQQqDMBBFryKzbkomoIaueo8iYepMaxYxkqhUx Ls32At0+f7/vL9DluQlw63aIcnqs49jAXOpoB9ofIvyXBiMNjUabRXlSYRdYB8dMTteQthcEmJ V25ae1mprsYUimJK8/OeUP2CUGboSDj7PMW3n4Ypn9Y97RYVKE9oGiQ02eP+NZ+mHax8DdMdxf AG3JDDXzgAAAA== X-Change-ID: 20251208-aspeed_mdio_add_dummy_read-587ab8808817 To: Andrew Lunn , Heiner Kallweit , Russell King , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Joel Stanley , Andrew Jeffery , Potin Lai CC: , , , , Jacky Chou X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1765278932; l=1877; i=jacky_chou@aspeedtech.com; s=20251031; h=from:subject:message-id; bh=Mg8PdAkgzIWHVGruAAz0jujfLeSjM7YjkzAbXqHp61U=; b=cIXKNFH4KlPuUxu8VYrzWB6g8Jw7ZigbsZTBDriQL/xeLWFu/8lzf993F8cPv+2+thMgn7WFZ 5ipiglIvxodDFOOpgnU/meEZJqwxMa6GpKHdo8UkSyqAU4WdN8iAItD X-Developer-Key: i=jacky_chou@aspeedtech.com; a=ed25519; pk=8XBx7KFM1drEsfCXTH9QC2lbMlGU4XwJTA6Jt9Mabdo= The Aspeed MDIO controller may return incorrect data when a read operation follows immediately after a write. Due to a controller bug, the subsequent read can latch stale data, causing the polling logic to terminate earlier than expected. To work around this hardware issue, insert a dummy read after each write operation. This ensures that the next actual read returns the correct data and prevents premature polling exit. This workaround has been verified to stabilize MDIO transactions on affected Aspeed platforms. Fixes: f160e99462c6 ("net: phy: Add mdio-aspeed") Signed-off-by: Jacky Chou --- Changes in v2: - Updated the Fixes: tag - Link to v1: https://lore.kernel.org/r/20251208-aspeed_mdio_add_dummy_read= -v1-1-0a1861ad2161@aspeedtech.com --- drivers/net/mdio/mdio-aspeed.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-aspeed.c index e55be6dc9ae7..7d11add3c05e 100644 --- a/drivers/net/mdio/mdio-aspeed.c +++ b/drivers/net/mdio/mdio-aspeed.c @@ -63,6 +63,13 @@ static int aspeed_mdio_op(struct mii_bus *bus, u8 st, u8= op, u8 phyad, u8 regad, =20 iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL); =20 + /* Workaround for read-after-write issue. + * The controller may return stale data if a read follows immediately + * after a write. A dummy read forces the hardware to update its + * internal state, ensuring that the next real read returns correct data. + */ + (void)ioread32(ctx->base + ASPEED_MDIO_CTRL); + return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl, !(ctrl & ASPEED_MDIO_CTRL_FIRE), ASPEED_MDIO_INTERVAL_US, --- base-commit: 0373d5c387f24de749cc22e694a14b3a7c7eb515 change-id: 20251208-aspeed_mdio_add_dummy_read-587ab8808817 Best regards, --=20 Jacky Chou