linux-kernel - RE: [PATCH net-next v3 4/4] net: fec: add phy_reset_after_clk

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Date:   Wed, 6 Dec 2017 08:41:03 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Richard Leitner <richard.leitner@...data.com>,
        Richard Leitner <dev@...l1n.net>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "frowand.list@...il.com" <frowand.list@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        "sergei.shtylyov@...entembedded.com" 
        <sergei.shtylyov@...entembedded.com>,
        "baruch@...s.co.il" <baruch@...s.co.il>,
        "david.wu@...k-chips.com" <david.wu@...k-chips.com>,
        "lukma@...x.de" <lukma@...x.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next v3 4/4] net: fec: add
 phy_reset_after_clk_enable() support

From: Richard Leitner <richard.leitner@...data.com> Sent: Wednesday, December 06, 2017 4:12 PM
>To: Andy Duan <fugang.duan@....com>; Richard Leitner <dev@...l1n.net>;
>robh+dt@...nel.org; mark.rutland@....com; andrew@...n.ch;
>f.fainelli@...il.com; frowand.list@...il.com
>Cc: davem@...emloft.net; geert+renesas@...der.be;
>sergei.shtylyov@...entembedded.com; baruch@...s.co.il; david.wu@...k-
>chips.com; lukma@...x.de; netdev@...r.kernel.org;
>devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
>Subject: Re: [PATCH net-next v3 4/4] net: fec: add
>phy_reset_after_clk_enable() support
>
>Hi Andy,
>
>On 12/06/2017 02:50 AM, Andy Duan wrote:
>> From: Richard Leitner <dev@...l1n.net> Sent: Tuesday, December 05,
>> 2017 9:26 PM
>>> Some PHYs (for example the SMSC LAN8710/LAN8720) doesn't allow
>>> turning the refclk on and off again during operation (according to their
>datasheet).
>>> Nonetheless exactly this behaviour was introduced for power saving
>>> reasons by commit e8fcfcd5684a ("net: fec: optimize the clock
>>> management to save power").
>>> Therefore add support for the phy_reset_after_clk_enable function
>>> from phylib to mitigate this issue.
>
>...
>
>>> diff --git a/drivers/net/ethernet/freescale/fec_main.c
>>> b/drivers/net/ethernet/freescale/fec_main.c
>>> index 610573855213..8c3d0fb7db20 100644
>>> --- a/drivers/net/ethernet/freescale/fec_main.c
>>> +++ b/drivers/net/ethernet/freescale/fec_main.c
>>> @@ -1862,6 +1862,8 @@ static int fec_enet_clk_enable(struct
>>> net_device *ndev, bool enable)
>>> 		ret = clk_prepare_enable(fep->clk_ref);
>>> 		if (ret)
>>> 			goto failed_clk_ref;
>>> +
>>> +		phy_reset_after_clk_enable(ndev->phydev);
>>> 	} else {
>>> 		clk_disable_unprepare(fep->clk_ahb);
>>> 		clk_disable_unprepare(fep->clk_enet_out);
>>> @@ -2860,6 +2862,11 @@ fec_enet_open(struct net_device *ndev)
>>> 	if (ret)
>>> 		goto err_enet_mii_probe;
>>>
>>> +	/* reset phy if needed here, due to the fact this is the first time we
>>> +	 * have the net_device to phy_driver link
>>> +	 */
>>> +	phy_reset_after_clk_enable(ndev->phydev);
>>> +
>>
>> The patch series look better.
>> But why does it need to reset phy here since phy already is hard reset after
>clock enable.
>
>The problem here is that in fec_enet_open() the fec_enet_clk_enable() call is
>done before the phy is probed. Therefore (as mentioned in the
>comment) there's no link from the net_device (ndev) to the phy_driver
>(which holds the flags).
>
>Any suggestions for a better solution are highly appreciated here! Thanks!
>
>regards;Richard.L

Okay, I see.

For the patch: Acked-by: Fugang Duan <fugang.duan@....com>