From nobody Tue Dec 16 17:01:00 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 D06DC28541A; Thu, 11 Dec 2025 06:25:08 +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=1765434312; cv=none; b=MDmouuW3y4IM7zp4zo/kNp5CHTEEN2WxRiX4dwojAcFrKMiEuRcNubXjIRYT48xezDEoruB4nsX7YgwRaRbh1FtY/+g0mTcyOj/l5akMKz2JTR86wd4nhspB44Apo1API208USVHhoZKvrLPwpd5SYI+syC7q5o0xQNgAU5XI3o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765434312; c=relaxed/simple; bh=/F4kIXDvh45WJxiCbdIwAGVfMvFPrac8MDCbVP75p2g=; h=From:Date:Subject:MIME-Version:Content-Type:Message-ID:To:CC; b=FN6VEv7b4MwbsLaFmSN65VNoWm6uvq1g3FPj8wrfvG1vUQBRAu61d0tLdwCt4gcQi0AXejngAfgm595BUI/H7Fp7/VmCcepVfXgjGiWGHsz+Z5LJloFvpM0VWwW8ndlVlK+vDdKN+ArKT4jGMAWm+3zHmCWmNDcvvTSQTh8v9Gk= 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; Thu, 11 Dec 2025 14:25:01 +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; Thu, 11 Dec 2025 14:25:01 +0800 From: Jacky Chou Date: Thu, 11 Dec 2025 14:24:58 +0800 Subject: [PATCH net v3] 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: <20251211-aspeed_mdio_add_dummy_read-v3-1-382868869004@aspeedtech.com> X-B4-Tracking: v=1; b=H4sIALljOmkC/43NQQ7CIBAF0Ks0rMUwaCl15T2MIVimlgWlgUpsm t5dghsTE+Pyz5+8v5KIwWIkp2olAZON1o85HHYV6QY93pFakzPhjNfAmaQ6TohGOWO90sYo83B uUQG1obVs9E1KJiU0JANTwN4+C34hI87kmo+DjbMPSxlMUKp/7AQUKNMgBWjDQcD5/TxjN+w77 4qd+KfX/vR49upeMAHiCK1sv7xt214iS3GuHgEAAA== 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: , , , , "Andrew Jeffery" , Jacky Chou X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1765434301; l=2016; i=jacky_chou@aspeedtech.com; s=20251031; h=from:subject:message-id; bh=/F4kIXDvh45WJxiCbdIwAGVfMvFPrac8MDCbVP75p2g=; b=oJptiug7G0Gd4SocdRv+VJ4ONlyM5fmP7zoWOeQc6wU3FZ/KkhT4lxdo14vQWCOtkRhz67Y2g 97WIqf9bH2XBjn3dkbiQSY0jjL20PVv1/htH/ayyKn+s8t/nwgFZKHH 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 Reviewed-by: Andrew Lunn --- Changes in v3: - Remove (void) - Link to v2: https://lore.kernel.org/r/20251209-aspeed_mdio_add_dummy_read= -v2-1-5f6061641989@aspeedtech.com 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..d6b9004c61dc 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. + */ + 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: 6bcb7727d9e612011b70d64a34401688b986d6ab change-id: 20251208-aspeed_mdio_add_dummy_read-587ab8808817 Best regards, --=20 Jacky Chou