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

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@vger.kernel.org
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Dylan Hung <redacted>
---
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),
+				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,

-- 
2.25.1

On Thu, Nov 25, 2021 at 10:44:32AM +0800, Dylan Hung wrote:

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@vger.kernel.org
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Dylan Hung <redacted>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

On Thu, Nov 25, 2021 at 10:44:32AM +0800, Dylan Hung wrote:

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@vger.kernel.org
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Dylan Hung <redacted>

Reviewed-by: Russell King (Oracle) <redacted>

Thanks.

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Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski [off-list ref]:

On Thu, 25 Nov 2021 10:44:32 +0800 you wrote:

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

[...]

Here is the summary with links:
  - [v2] mdio: aspeed: Fix "Link is Down" issue
    https://git.kernel.org/netdev/net/c/9dbe33cf371b

You are awesome, thank you!
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