netdev - Re: [PATCH] net: mv643xx_eth: support MII/GMII/RGMII modes

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Date:   Fri, 30 Sep 2022 22:28:36 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     David Yang <mmyangfl@...il.com>
Cc:     Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: mv643xx_eth: support MII/GMII/RGMII modes

On Sat, Oct 01, 2022 at 03:49:23AM +0800, David Yang wrote:
> On device reset all ports are automatically set to RGMII mode. MII
> mode must be explicitly enabled.
> 
> If SoC has two Ethernet controllers, by setting both of them into MII
> mode, the first controller enters GMII mode, while the second
> controller is effectively disabled. This requires configuring (and
> maybe enabling) the second controller in the device tree, even though
> it cannot be used.
> 
> Signed-off-by: David Yang <mmyangfl@...il.com>
> ---
>  drivers/net/ethernet/marvell/mv643xx_eth.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/net/ethernet/marvell/mv643xx_eth.c b/drivers/net/ethernet/marvell/mv643xx_eth.c
> index b6be0552a..e2216ce5e 100644
> --- a/drivers/net/ethernet/marvell/mv643xx_eth.c
> +++ b/drivers/net/ethernet/marvell/mv643xx_eth.c
> @@ -108,6 +108,7 @@ static char mv643xx_eth_driver_version[] = "1.4";
>  #define TXQ_COMMAND			0x0048
>  #define TXQ_FIX_PRIO_CONF		0x004c
>  #define PORT_SERIAL_CONTROL1		0x004c
> +#define  RGMII_EN			0x00000008
>  #define  CLK125_BYPASS_EN		0x00000010
>  #define TX_BW_RATE			0x0050
>  #define TX_BW_MTU			0x0058
> @@ -1245,6 +1246,21 @@ static void mv643xx_eth_adjust_link(struct net_device *dev)
>  
>  out_write:
>  	wrlp(mp, PORT_SERIAL_CONTROL, pscr);
> +
> +	/* If two Ethernet controllers present in the SoC, MII modes follow the
> +	 * following matrix:
> +	 *
> +	 * Port0 Mode	Port1 Mode	Port0 RGMII_EN	Port1 RGMII_EN
> +	 * RGMII	RGMII		1		1
> +	 * RGMII	MII/MMII	1		0
> +	 * MII/MMII	RGMII		0		1
> +	 * GMII		N/A		0		0
> +	 *
> +	 * To enable GMII on Port 0, Port 1 must also disable RGMII_EN too.
> +	 */
> +	if (!phy_interface_is_rgmii(dev->phydev))
> +		wrlp(mp, PORT_SERIAL_CONTROL1,
> +		     rdlp(mp, PORT_SERIAL_CONTROL1) & ~RGMII_EN);

I could be reading this wrong, but doesn't this break the third line:

> +	 * MII/MMII	RGMII		0		1

Port 1 probes first, phy_interface is rgmii, so nothing happens, port1
RGMII_EN is left true.

Port 0 then probes, MII/MMII is not RGMII, so port1 RGMII_EN is
cleared, breaking port1.

I think you need to be more specific with the comparison.

  Andrew