[PATCH v2] mdio: aspeed: Fix "Link is Down" issue

Dylan Hung dylan_hung at aspeedtech.com
Thu Nov 25 13:44:32 AEDT 2021

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

Fixes: f160e99462c6 ("net: phy: Add mdio-aspeed")
Cc: stable at vger.kernel.org
Reviewed-by: Joel Stanley <joel at jms.id.au>
Signed-off-by: Dylan Hung <dylan_hung at aspeedtech.com>
v2: revise commit message

 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 cad820568f75..966c3b4ad59d 100644
--- a/drivers/net/mdio/mdio-aspeed.c
+++ b/drivers/net/mdio/mdio-aspeed.c
@@ -61,6 +61,13 @@ static int aspeed_mdio_read(struct mii_bus *bus, int addr, int regnum)
 	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
+	rc = readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
+				!(ctrl & ASPEED_MDIO_CTRL_FIRE),
+	if (rc < 0)
+		return rc;
 	rc = readl_poll_timeout(ctx->base + ASPEED_MDIO_DATA, data,

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