Re: [PATCH net] net: phy: rtl8211f: do a double read to get real time link status
From: Heiner Kallweit
Date: Fri Aug 09 2019 - 16:05:51 EST
On 09.08.2019 06:57, Yonglong Liu wrote:
> 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
>>> 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.
> 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
> 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  .... 27.182632: mdio_access: mii-0000:bd:00.3 write phy:0x07 reg:0x00 val:0x1240
> kworker/u257:1-670  .... 27.184670: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x01 val:0x7989
Instead of using this fixed delay, the following experimental patch
considers that fact that between triggering aneg start and actual
start of aneg (incl. clearing aneg-complete bit) Clause 22 requires
a PHY to keep bit 0.9 (aneg restart) set.
Could you please test this instead of the fixed-delay patch?
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index b039632de..163295dbc 100644
@@ -1741,7 +1741,17 @@ EXPORT_SYMBOL(genphy_aneg_done);
int genphy_update_link(struct phy_device *phydev)
- int status;
+ int status = 0, bmcr;
+ bmcr = phy_read(phydev, MII_BMCR);
+ if (bmcr < 0)
+ return bmcr;
+ /* Autoneg is being started, therefore disregard BMSR value and
+ * report link as down.
+ if (bmcr & BMCR_ANRESTART)
+ goto done;
/* The link state is latched low so that momentary link
* drops can be detected. Do not double-read the status