linux-kernel - RE: [PATCH] net: fec: fix enet

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Message-ID: <BN3PR0301MB1219C4D8E1B09F1AE27E18FAF5020@BN3PR0301MB1219.namprd03.prod.outlook.com>
Date:	Sat, 28 Nov 2015 13:13:16 +0000
From:	Duan Andy <fugang.duan@...escale.com>
To:	Lothar Wa?mann <LW@...O-electronics.de>,
	Andrew Lunn <andrew@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Fabio Estevam <Fabio.Estevam@...escale.com>,
	Kevin Hao <haokexin@...il.com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Philippe Reynes <tremyfr@...il.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Stefan Agner <stefan@...er.ch>
Subject: RE: [PATCH] net: fec: fix enet_out clock handling

From: Lothar Waßmann <LW@...O-electronics.de> Sent: Friday, November 27, 2015 9:39 PM
> To: Andrew Lunn; David S. Miller; Estevam Fabio-R49496; Kevin Hao; Lothar
> Waßmann; Lucas Stach; Duan Fugang-B38611; Philippe Reynes; Russell King;
> Uwe Kleine-König; linux-kernel@...r.kernel.org; netdev@...r.kernel.org;
> Stefan Agner
> Subject: [PATCH] net: fec: fix enet_out clock handling
> 
> When ENET_OUT is being used as reference clock for an external PHY, the
> clock must not be disabled while the PHY is active. Otherwise the PHY may
> lose its internal state and require a reset to become functional again.
> 
> A symptom for this bug is a network interface that constantly toggles
> between UP and DOWN state:
> fec 800f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control
> rx/tx fec 800f0000.ethernet eth0: Link is Down fec 800f0000.ethernet eth0:
> Link is Up - 100Mbps/Full - flow control rx/tx fec 800f0000.ethernet eth0:
> Link is Down [...]
> 
> Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> ---
>  drivers/net/ethernet/freescale/fec_main.c | 34 +++++++++++++------------
> ------
>  1 file changed, 14 insertions(+), 20 deletions(-)
> 

When MAC is not ready with clocks disabled,  it is not necessary to supply clock for PHY. In fact, PHY also is not ready, why does it need clock ?
For your problem, you must add PHY reset in your dts file to resolve your problem.

I don't agree with this patch.

> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index d2328fc..d9df4c5 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -1857,11 +1857,6 @@ static int fec_enet_clk_enable(struct net_device
> *ndev, bool enable)
>  		ret = clk_prepare_enable(fep->clk_ahb);
>  		if (ret)
>  			return ret;
> -		if (fep->clk_enet_out) {
> -			ret = clk_prepare_enable(fep->clk_enet_out);
> -			if (ret)
> -				goto failed_clk_enet_out;
> -		}
>  		if (fep->clk_ptp) {
>  			mutex_lock(&fep->ptp_clk_mutex);
>  			ret = clk_prepare_enable(fep->clk_ptp); @@ -1873,35
> +1868,26 @@ static int fec_enet_clk_enable(struct net_device *ndev, bool
> enable)
>  			}
>  			mutex_unlock(&fep->ptp_clk_mutex);
>  		}
> -		if (fep->clk_ref) {
> -			ret = clk_prepare_enable(fep->clk_ref);
> -			if (ret)
> -				goto failed_clk_ref;
> -		}
> +		ret = clk_prepare_enable(fep->clk_ref);
> +		if (ret)
> +			goto failed_clk_ref;
>  	} else {
>  		clk_disable_unprepare(fep->clk_ahb);
> -		if (fep->clk_enet_out)
> -			clk_disable_unprepare(fep->clk_enet_out);
>  		if (fep->clk_ptp) {
>  			mutex_lock(&fep->ptp_clk_mutex);
>  			clk_disable_unprepare(fep->clk_ptp);
>  			fep->ptp_clk_on = false;
>  			mutex_unlock(&fep->ptp_clk_mutex);
>  		}
> -		if (fep->clk_ref)
> -			clk_disable_unprepare(fep->clk_ref);
> +		clk_disable_unprepare(fep->clk_ref);
>  	}
> 
>  	return 0;
> 
>  failed_clk_ref:
> -	if (fep->clk_ref)
> -		clk_disable_unprepare(fep->clk_ref);
> +	clk_disable_unprepare(fep->clk_ref);
>  failed_clk_ptp:
> -	if (fep->clk_enet_out)
> -		clk_disable_unprepare(fep->clk_enet_out);
> -failed_clk_enet_out:
> -		clk_disable_unprepare(fep->clk_ahb);
> +	clk_disable_unprepare(fep->clk_ahb);
> 
>  	return ret;
>  }
> @@ -3425,6 +3411,10 @@ fec_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto failed_clk;
> 
> +	ret = clk_prepare_enable(fep->clk_enet_out);
> +	if (ret)
> +		goto failed_clk_enet_out;
> +
>  	ret = clk_prepare_enable(fep->clk_ipg);
>  	if (ret)
>  		goto failed_clk_ipg;
> @@ -3509,6 +3499,8 @@ failed_init:
>  	if (fep->reg_phy)
>  		regulator_disable(fep->reg_phy);
>  failed_regulator:
> +	clk_disable_unprepare(fep->clk_enet_out);
> +failed_clk_enet_out:
>  	clk_disable_unprepare(fep->clk_ipg);
>  failed_clk_ipg:
>  	fec_enet_clk_enable(ndev, false);
> @@ -3531,6 +3523,8 @@ fec_drv_remove(struct platform_device *pdev)
>  	fec_ptp_stop(pdev);
>  	unregister_netdev(ndev);
>  	fec_enet_mii_remove(fep);
> +	fec_enet_clk_enable(ndev, false);
> +	clk_disable_unprepare(fep->clk_enet_out);
>  	if (fep->reg_phy)
>  		regulator_disable(fep->reg_phy);
>  	of_node_put(fep->phy_node);
> --
> 2.1.4