linux-kernel - [PATCH 5.4 22/92] mdio: aspeed: Fix "Link is Down" issue

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Message-Id: <20211129181708.151769080@linuxfoundation.org>
Date:   Mon, 29 Nov 2021 19:17:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Stanley <joel@....id.au>,
        Dylan Hung <dylan_hung@...eedtech.com>,
        Andrew Lunn <andrew@...n.ch>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 5.4 22/92] mdio: aspeed: Fix "Link is Down" issue

From: Dylan Hung <dylan_hung@...eedtech.com>

commit 9dbe33cf371bd70330858370bdbc35c7668f00c3 upstream.

The issue happened randomly in runtime.  The message "Link is Down" is
popped but soon it recovered to "Link is Up".

The "Link is Down" results from the incorrect read data for reading the
PHY register via MDIO bus.  The correct sequence for reading the data
shall be:
1. fire the command
2. wait for command done (this step was missing)
3. wait for data idle
4. read data from data register

Cc: stable@...r.kernel.org
Fixes: f160e99462c6 ("net: phy: Add mdio-aspeed")
Reviewed-by: Joel Stanley <joel@....id.au>
Signed-off-by: Dylan Hung <dylan_hung@...eedtech.com>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Link: https://lore.kernel.org/r/20211125024432.15809-1-dylan_hung@aspeedtech.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/phy/mdio-aspeed.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/net/phy/mdio-aspeed.c
+++ b/drivers/net/phy/mdio-aspeed.c
@@ -61,6 +61,13 @@ static int aspeed_mdio_read(struct mii_b
 
 	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
 
+	rc = readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
+				!(ctrl & ASPEED_MDIO_CTRL_FIRE),
+				ASPEED_MDIO_INTERVAL_US,
+				ASPEED_MDIO_TIMEOUT_US);
+	if (rc < 0)
+		return rc;
+
 	rc = readl_poll_timeout(ctx->base + ASPEED_MDIO_DATA, data,
 				data & ASPEED_MDIO_DATA_IDLE,
 				ASPEED_MDIO_INTERVAL_US,