linux-kernel - Re: [PATCH net] net: phy: rtl8211f: do a double read to get real time link status

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Message-ID: <414c6809-86a3-506c-b7b0-a32b7cd72fd6@huawei.com>
Date:   Fri, 9 Aug 2019 12:57:48 +0800
From:   Yonglong Liu <liuyonglong@...wei.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
        <salil.mehta@...wei.com>, <yisen.zhuang@...wei.com>,
        <shiju.jose@...wei.com>
Subject: Re: [PATCH net] net: phy: rtl8211f: do a double read to get real time
 link status



On 2019/8/9 4:34, Andrew Lunn wrote:
> On Thu, Aug 08, 2019 at 10:01:39PM +0200, Heiner Kallweit wrote:
>> On 08.08.2019 21:40, Andrew Lunn wrote:
>>>> @@ -568,6 +568,11 @@ int phy_start_aneg(struct phy_device *phydev)
>>>>  	if (err < 0)
>>>>  		goto out_unlock;
>>>>  
>>>> +	/* The PHY may not yet have cleared aneg-completed and link-up bit
>>>> +	 * w/o this delay when the following read is done.
>>>> +	 */
>>>> +	usleep_range(1000, 2000);
>>>> +
>>>
>>> Hi Heiner
>>>
>>> Does 802.3 C22 say anything about this?
>>>
>> C22 says:
>> "The Auto-Negotiation process shall be restarted by setting bit 0.9 to a logic one. This bit is self-
>> clearing, and a PHY shall return a value of one in bit 0.9 until the Auto-Negotiation process has been
>> initiated."
>>
>> Maybe we should read bit 0.9 in genphy_update_link() after having read BMSR and report
>> aneg-complete and link-up as false (no matter of their current value) if 0.9 is set.
> 
> Yes. That sounds sensible.
> 
>      Andrew
> 
> .
> 

Hi Heiner:
	I have test more than 50 times, it works. Previously less
than 20 times must be recurrence. so I think this patch solved the
problem.
	And I checked about 40 times of the time gap between read
and autoneg started, all of them is more than 2ms, as below:

  kworker/u257:1-670   [015] ....    27.182632: mdio_access: mii-0000:bd:00.3 write phy:0x07 reg:0x00 val:0x1240
  kworker/u257:1-670   [015] ....    27.184670: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x01 val:0x7989