netdev - Re: [PATCH] net:phy: Fix "Link is Down" issue

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Date:   Wed, 24 Nov 2021 10:05:45 +0000
From:   Joel Stanley <joel@....id.au>
To:     Dylan Hung <dylan_hung@...eedtech.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Networking <netdev@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Russell King <linux@...linux.org.uk>, hkallweit1@...il.com,
        Andrew Lunn <andrew@...n.ch>, BMC-SW <BMC-SW@...eedtech.com>
Subject: Re: [PATCH] net:phy: Fix "Link is Down" issue

On Wed, 24 Nov 2021 at 06:11, Dylan Hung <dylan_hung@...eedtech.com> 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

I consulted the datasheet and it doesn't mention this. Perhaps
something to be added?

Reviewed-by: Joel Stanley <joel@....id.au>

>
> Fixes: a9770eac511a ("net: mdio: Move MDIO drivers into a new subdirectory")

I think this should be:

Fixes: f160e99462c6 ("net: phy: Add mdio-aspeed")

We should cc stable too.

> Signed-off-by: Dylan Hung <dylan_hung@...eedtech.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 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
>