netdev - Re: [PATCH] net: ethernet: mediatek: fix warning in phy_start

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Message-ID: <7acce775-4ab7-c867-c801-25ee004f6b38@gmail.com>
Date:   Tue, 8 Jan 2019 19:37:35 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Frank Wunderlich <frank-w@...lic-files.de>,
        Felix Fietkau <nbd@...nwrt.org>,
        John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...nel.org>,
        Nelson Chang <nelson.chang@...iatek.com>,
        "David S. Miller" <davem@...emloft.net>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: ethernet: mediatek: fix warning in phy_start_aneg

On 08.01.2019 17:05, Frank Wunderlich wrote:
> From: Sean Wang <sean.wang@...nel.org>
> 
> linux 5.0-rc1 shows following warning on bpi-r2/mt7623 bootup:
> 
> [ 5.170597] WARNING: CPU: 3 PID: 1 at drivers/net/phy/phy.c:548 phy_start_aneg+0x110/0x144
> [ 5.178826] called from state READY
> ....
> [ 5.264111] [<c0629fd4>] (phy_start_aneg) from [<c0e3e720>] (mtk_init+0x414/0x47c)
> [ 5.271630] r7:df5f5eec r6:c0f08c48 r5:00000000 r4:dea67800
> [ 5.277256] [<c0e3e30c>] (mtk_init) from [<c07dabbc>] (register_netdevice+0x98/0x51c)
> [ 5.285035] r8:00000000 r7:00000000 r6:c0f97080 r5:c0f08c48 r4:dea67800
> [ 5.291693] [<c07dab24>] (register_netdevice) from [<c07db06c>] (register_netdev+0x2c/0x44)
> [ 5.299989] r8:00000000 r7:dea2e608 r6:deacea00 r5:dea2e604 r4:dea67800
> [ 5.306646] [<c07db040>] (register_netdev) from [<c06326d8>] (mtk_probe+0x668/0x7ac)
> [ 5.314336] r5:dea2e604 r4:dea2e040
> [ 5.317890] [<c0632070>] (mtk_probe) from [<c05a78fc>] (platform_drv_probe+0x58/0xa8)
> [ 5.325670] r10:c0f86bac r9:00000000 r8:c0fbe578 r7:00000000 r6:c0f86bac r5:00000000
> [ 5.333445] r4:deacea10
> [ 5.335963] [<c05a78a4>] (platform_drv_probe) from [<c05a5248>] (really_probe+0x2d8/0x424)
> 
> maybe other boards using this generic driver are affected
> 
Good that we added this warning to phylib, it seems usage of the phylib
API in this driver can be improved.

> Signed-off-by: Frank Wunderlich <frank-w@...lic-files.de>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index 399f565dd85a..e48c06874a85 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -356,6 +356,7 @@ static int mtk_phy_connect(struct net_device *dev)
>  	linkmode_copy(dev->phydev->advertising, dev->phydev->supported);
>  	linkmode_set_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
>  			 dev->phydev->advertising);
> +	phy_start(dev->phydev);
>  	phy_start_aneg(dev->phydev);
>  

In mtk_phy_connect() I would say this complete block can be removed.
All this is handled internally by phylib.

	dev->phydev->autoneg = AUTONEG_ENABLE;
	dev->phydev->speed = 0;
	dev->phydev->duplex = 0;

	phy_set_max_speed(dev->phydev, SPEED_1000);
	phy_support_asym_pause(dev->phydev);
	linkmode_copy(dev->phydev->advertising, dev->phydev->supported);
	linkmode_set_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
			 dev->phydev->advertising);
	phy_start_aneg(dev->phydev);

Could you please test this?

- phy_set_max_speed() is only needed if you want to reduce the
  max speed, typically if the PHY supports 1Gbps but the MAC
  supports 100Mbps only.

- The pause parameters are autonegotiated. Except you have a specific
  need you normally don't need to manually fiddle with this.

- phy_start_aneg() is called implicitly by the phylib state machine,
  you shouldn't call it manually except you have a good excuse.

And a further proposal:
Instead of the open-coded dev_info() in mtk_phy_connect_node()
you could use phy_attached_info().

>  	of_node_put(np);
> @@ -1821,7 +1822,6 @@ static int mtk_open(struct net_device *dev)
>  	else
>  		refcount_inc(&eth->dma_refcnt);
>  
> -	phy_start(dev->phydev);
>  	netif_start_queue(dev);
>  
>  	return 0;
> 

Calling phy_start() in the ndo_open callback is fine, you can leave
it there.