linux-kernel - Re: [PATCH] dp83640: Ensure against premature access to PHY registers after reset

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Message-ID: <8760541cy4.fsf@gmail.com>
Date:   Fri, 06 Apr 2018 19:06:59 +0200
From:   Esben Haabendal <esben.haabendal@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     andrew@...n.ch, netdev@...r.kernel.org, richardcochran@...il.com,
        f.fainelli@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dp83640: Ensure against premature access to PHY registers after reset

David Miller <davem@...emloft.net> writes:

> From: Andrew Lunn <andrew@...n.ch>
> Date: Fri, 6 Apr 2018 16:14:10 +0200
>
>> On Fri, Apr 06, 2018 at 04:05:40PM +0200, Esben Haabendal wrote:
>>> From: Esben Haabendal <eha@...f.com>
>>> 
>>> Signed-off-by: Esben Haabendal <eha@...f.com>
>>> ---
>>>  drivers/net/phy/dp83640.c | 17 +++++++++++++++++
>>>  1 file changed, 17 insertions(+)
>>> 
>>> diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
>>> index 654f42d00092..48403170096a 100644
>>> --- a/drivers/net/phy/dp83640.c
>>> +++ b/drivers/net/phy/dp83640.c
>>> @@ -1207,6 +1207,22 @@ static void dp83640_remove(struct phy_device *phydev)
>>>  	kfree(dp83640);
>>>  }
>>>  
>>> +static int dp83640_soft_reset(struct phy_device *phydev)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = genphy_soft_reset(phydev);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	/* From DP83640 datasheet: "Software driver code must wait 3 us
>>> +	 * following a software reset before allowing further serial MII
>>> +	 * operations with the DP83640." */
>>> +	udelay(3);
>> 
>> Hi Esben
>> 
>> The accuracy of udelay() is not guaranteed. So you probably want to be
>> a bit pessimistic, and use 10.

Ok, will do.

/Esben