netdev - Re: [PATCH 2/2] Reset PHY in phy_init_hw() before interrupt configuration

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Date:   Wed, 29 Apr 2020 19:06:11 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     "Badel, Laurent" <LaurentBadel@...on.com>,
        "fugang.duan@....com" <fugang.duan@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "richard.leitner@...data.com" <richard.leitner@...data.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "alexander.levin@...rosoft.com" <alexander.levin@...rosoft.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc:     "Quette, Arnaud" <ArnaudQuette@...on.com>
Subject: Re: [PATCH 2/2] Reset PHY in phy_init_hw() before interrupt
 configuration

On 29.04.2020 11:03, Badel, Laurent wrote:
> Description: this patch adds a reset of the PHY in phy_init_hw() 
> for PHY drivers bearing the PHY_RST_AFTER_CLK_EN flag.
> 
> Rationale: due to the PHY reset reverting the interrupt mask to default, 
> it is necessary to either perform the reset before PHY configuration, 
> or re-configure the PHY after reset. This patch implements the former
> as it is simpler and more generic. 
> 
> Fixes: 1b0a83ac04e383e3bed21332962b90710fcf2828 ("net: fec: add phy_reset_after_clk_enable() support")
> Signed-off-by: Laurent Badel <laurentbadel@...on.com>
> 
> ---
>  drivers/net/phy/phy_device.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 28e3c5c0e..2cc511364 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -1082,8 +1082,11 @@ int phy_init_hw(struct phy_device *phydev)
>  {
>  	int ret = 0;
>  
> -	/* Deassert the reset signal */
> -	phy_device_reset(phydev, 0);
> +	/* Deassert the reset signal
> +	 * If the PHY needs a reset, do it now
> +	 */
> +	if (!phy_reset_after_clk_enable(phydev))

If reset is asserted when entering phy_init_hw(), then
phy_reset_after_clk_enable() basically becomes a no-op.
Still it should work as expected due to the reset signal being
deasserted. It would be worth describing in the comment
why the code still works in this case.

> +		phy_device_reset(phydev, 0);
>  
>  	if (!phydev->drv)
>  		return 0;
>