netdev - RE: [PATCHv3 net-next] net: fec: Ensure clocks are enabled while using mdio bus

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Date:	Tue, 23 Jun 2015 01:25:36 +0000
From:	Duan Andy <fugang.duan@...escale.com>
To:	Andrew Lunn <andrew@...n.ch>, David Miller <davem@...emloft.net>
CC:	Cory Tusar <cory.tusar@...1solutions.com>,
	netdev <netdev@...r.kernel.org>
Subject: RE: [PATCHv3 net-next] net: fec: Ensure clocks are enabled while
 using mdio bus

From: Andrew Lunn <andrew@...n.ch> Sent: Sunday, June 21, 2015 2:38 AM
> To: David Miller
> Cc: Duan Fugang-B38611; Duan Fugang-B38611; Cory Tusar; netdev; Andrew
> Lunn
> Subject: [PATCHv3 net-next] net: fec: Ensure clocks are enabled while
> using mdio bus
> 
> When a switch is attached to the mdio bus, the mdio bus can be used while
> the interface is not open. If the IPG clock are not enabled, MDIO
> reads/writes will simply time out. So enable the clock before starting a
> transaction, and disable it afterwards. The CCF performs reference
> counting so the clock will only be disabled if there are no other users.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
> 
> v3:
>  Return the error code from clk_prepare_enable()
> v2:
>  Only enable the IGP clock.
> 
>  drivers/net/ethernet/freescale/fec_main.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index bf4cf3fbb5f2..8d9b1fd175f7 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -65,6 +65,7 @@
> 
>  static void set_multicast_list(struct net_device *ndev);  static void
> fec_enet_itr_coal_init(struct net_device *ndev);
> +static int fec_enet_clk_enable(struct net_device *ndev, bool enable);
> 
>  #define DRIVER_NAME	"fec"
> 
> @@ -1764,6 +1765,11 @@ static int fec_enet_mdio_read(struct mii_bus *bus,
> int mii_id, int regnum)  {
>  	struct fec_enet_private *fep = bus->priv;
>  	unsigned long time_left;
> +	int ret;
> +
> +	ret = clk_prepare_enable(fep->clk_ipg);
> +	if (ret)
> +		return ret;
> 
>  	fep->mii_timeout = 0;
>  	init_completion(&fep->mdio_done);
> @@ -1779,11 +1785,14 @@ static int fec_enet_mdio_read(struct mii_bus *bus,
> int mii_id, int regnum)
>  	if (time_left == 0) {
>  		fep->mii_timeout = 1;
>  		netdev_err(fep->netdev, "MDIO read timeout\n");
> +		clk_disable_unprepare(fep->clk_ipg);
>  		return -ETIMEDOUT;
>  	}
> 
> -	/* return value */
> -	return FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
> +	ret = FEC_MMFR_DATA(readl(fep->hwp + FEC_MII_DATA));
> +	clk_disable_unprepare(fep->clk_ipg);
> +
> +	return ret;
>  }
> 

I suggest you use runtime pm to enable/disable clock for performance consideration. Not every time for mdio bus access needs to enable/disable clock.


>  static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int
> regnum, @@ -1791,10 +1800,15 @@ static int fec_enet_mdio_write(struct
> mii_bus *bus, int mii_id, int regnum,  {
>  	struct fec_enet_private *fep = bus->priv;
>  	unsigned long time_left;
> +	int ret;
> 
>  	fep->mii_timeout = 0;
>  	init_completion(&fep->mdio_done);
> 
> +	ret = clk_prepare_enable(fep->clk_ipg);
> +	if (ret)
> +		return ret;
> +
>  	/* start a write op */
>  	writel(FEC_MMFR_ST | FEC_MMFR_OP_WRITE |
>  		FEC_MMFR_PA(mii_id) | FEC_MMFR_RA(regnum) | @@ -1807,9
> +1821,12 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int
> mii_id, int regnum,
>  	if (time_left == 0) {
>  		fep->mii_timeout = 1;
>  		netdev_err(fep->netdev, "MDIO write timeout\n");
> +		clk_disable_unprepare(fep->clk_ipg);
>  		return -ETIMEDOUT;
>  	}
> 
> +	clk_disable_unprepare(fep->clk_ipg);
> +
>  	return 0;
>  }
> 
> --
> 2.1.4

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