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Message-ID: <56E978C9.4080000@ti.com>
Date: Wed, 16 Mar 2016 11:16:25 -0400
From: Murali Karicheri <m-karicheri2@...com>
To: Florian Fainelli <f.fainelli@...il.com>, <johan@...nel.org>,
"open list:TI NETCP ETHERNET DRIVER" <netdev@...r.kernel.org>,
"Kwok, WingMan" <w-kwok2@...com>, Andrew Lunn <andrew@...nc.ch>,
<opendmb@...il.com>
Subject: Re: Micrel Phy - Is there a way to configure the Phy not to do 802.3x
flow control?
On 03/16/2016 11:08 AM, Murali Karicheri wrote:
> On 03/11/2016 02:51 PM, Florian Fainelli wrote:
>> On 11/03/16 10:31, Murali Karicheri wrote:
>>> On 03/10/2016 02:38 PM, Murali Karicheri wrote:
>>>> On 03/10/2016 01:05 PM, Florian Fainelli wrote:
>>>>> On 10/03/16 08:48, Murali Karicheri wrote:
>>>>>> On 03/03/2016 07:16 PM, Florian Fainelli wrote:
>>>>>>> On 03/03/16 14:18, Murali Karicheri wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> We are using Micrel Phy in one of our board and wondering if we can force the
>>>>>>>> Phy to disable flow control at start. I have a 1G ethernet switch connected
>>>>>>>> to Phy and the phy always enable flow control. I would like to configure the
>>>>>>>> phy not to flow control. Is that possible and if yes, what should I do in the
>>>>>>>> my Ethernet driver to tell the Phy not to enable flow control?
>>>>>>>
>>>>>>> The PHY is not doing flow control per-se, your pseudo Ethernet MAC in
>>>>>>> the switch is doing, along with the link partner advertising support for
>>>>>>> it. You would want to make sure that your PHY device interface (provided
>>>>>>> that you are using the PHY library) is not starting with Pause
>>>>>>> advertised, but it could be supported.
>>>>>>
>>>>>> Understood that Phy is just advertise FC. The Micrel phy for 9031 advertise
>>>>>> by default FC supported. After negotiation, I see that Phylib provide the
>>>>>> link status with parameter pause = 1, asym_pause = 1. How do I tell the Phy not
>>>>>> to advertise?
>>>>>>
>>>>>> I call following sequence in the Ethernet driver.
>>>>>>
>>>>>> of_phy_connect(x,y,hndlr,a,z);
>>>>>
>>>>> Here you should be able to change phydev->advertising and
>>>>> phydev->supported to mask the ADVERTISED_Pause | ADVERTISED_AsymPause
>>>>> bits and have phy_start() restart with that which should disable pause
>>>>> and asym_pause as seen by your adjust_link handler.
>>>>>
>>>> Ok. Good point. I will try this. Thanks for your suggestion.
>>>>
>>> I had to make following changes to the phy_device.c to allow the phy device
>>> report maximum common flow control capability to Ethernet driver through
>>> handler. My driver code looks like this.
>>>
>>> slave->phy = of_phy_connect(gbe_intf->ndev,
>>> slave->phy_node,
>>> hndlr, 0,
>>> phy_mode);
>>> if (!slave->phy) {
>>> dev_err(priv->dev, "phy not found on slave %d\n",
>>> slave->slave_num);
>>> return -ENODEV;
>>> }
>>> dev_dbg(priv->dev, "phy found: id is: 0x%s\n",
>>> dev_name(&slave->phy->dev));
>>>
>>> slave->phy->supported &=
>>> ~(SUPPORTED_Pause | SUPPORTED_Asym_Pause);
>>> slave->phy->advertising = slave->phy->supported;
>>> phy_start(slave->phy);
>>> phy_read_status(slave->phy);
>>>
>>> And then in the phy_device.c, I did to get flow control off reported in
>>> handler for link status update.
>>
>>
>>
>>>
>>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>>> index d551df6..55412ad 100644
>>> --- a/drivers/net/phy/phy_device.c
>>> +++ b/drivers/net/phy/phy_device.c
>>> @@ -1021,8 +1021,8 @@ int genphy_read_status(struct phy_device *phydev)
>>> phydev->duplex = DUPLEX_FULL;
>>>
>>> if (phydev->duplex == DUPLEX_FULL) {
>>> - phydev->pause = lpa & LPA_PAUSE_CAP ? 1 : 0;
>>> - phydev->asym_pause = lpa & LPA_PAUSE_ASYM ? 1 : 0;
>>> + phydev->pause = adv & lpa & LPA_PAUSE_CAP ? 1 : 0;
>>> + phydev->asym_pause = adv & lpa & LPA_PAUSE_ASYM ? 1 : 0;
>>
>> What it means before your patch is that flow control is reported to the
>> PHY device if the link partner advertises that, with your patch applied,
>> it is reported only if the link partner and yourself advertise flow control.
>>
>> You seem to be willing to have phydev->pause and phydev->asym_pause
>> reflect the resolved pause capability, as opposed to the link partner's
>> pause capability, which I am not convinced is correct here, because we
>> need to take into account the user-configured pause configuration as
>> well. Your adjust_link function should be the one deciding whether pause
>> frame advertising and enabling is appropriate based on: locally
>> configured pause settings (enabled, disabled, autoneg) and the link
>> partner's pause capability.
>>
>> I do agree that the two fields are confusing and poorly documented, and
>> we should probably be consolidating the pause frame behavior in PHYLIB
>> as opposed to letting drivers deal with like e.g: gianfar, bcm63xx_enet,
>> tg3 etc.
>>
>>>
>>> Could you explain, why the common maximum capability is not reported to the
>>> driver as per standard?? Or Am I understood it wrong?
>>
>> I do not understand the question, what is "maximum capability" in that
>> context and what standard are you refering to?
>>
> I assume the Phylib is responsible for deciding what is the flow
> control pause and asym pause status to the driver through adjust_link.
> When driver starts the phy, it also tells its capabilities (for example
> it can reset some of the capabilities available in the Phy driver. In this
> particular case, Pause is a feature supported by Micrel phy. I have reset
> this feature in my driver by resetting this feature bit in the phy_device
> as suggested earlier in this discussion). So phylib has all knowledge
> available to disable flow control in this scenario even if LP is capable
> of flow control. Wondering why every driver has to take this decision
> again to enable or disable flow control instead of telling the driver
> what to do.
What I meant is if driver tells phy not advertise, then adjust_link should
reflect the same. i.e both pause and asym_pause should be off.
Murali
>
> Looks like Marvel driver (reproduced below) does this logic. I think the
> 802.3x flow control states, but I don't have access to the standard documentation.
> However I find the documentation at
> http://www.studioreti.it/slide/08_SwFlowContr_E_A.pdf.
>
> Page 17 states the behavior based on Local device & Link partner's
> capabilities. Probably adjust_link() should tell the outcome in pause
> and asym_pause so that driver can enable/disable fc. Also user's action
> to be taken into account as well so that fc can be disabled if desired.
>
> Code from drivers/net/phy/marvel.c
>
> static int marvell_read_status(struct phy_device *phydev)
> {
>
> int adv;
> int err;
> int lpa;
> int lpagb;
> int status = 0;
>
> /* Update the link, but return if there
> * was an error */
> err = genphy_update_link(phydev);
> if (err)
> return err;
>
> if (AUTONEG_ENABLE == phydev->autoneg) {
> status = phy_read(phydev, MII_M1011_PHY_STATUS);
> if (status < 0)
> return status;
>
> lpa = phy_read(phydev, MII_LPA);
> if (lpa < 0)
> return lpa;
>
> lpagb = phy_read(phydev, MII_STAT1000);
> if (lpagb < 0)
> return lpagb;
>
> adv = phy_read(phydev, MII_ADVERTISE);
> if (adv < 0)
> return adv;
>
> phydev->lp_advertising = mii_stat1000_to_ethtool_lpa_t(lpagb) |
> mii_lpa_to_ethtool_lpa_t(lpa);
>
> lpa &= adv;
>
> if (status & MII_M1011_PHY_STATUS_FULLDUPLEX int adv;
> int err;
> int lpa;
> int lpagb;
> int status = 0;
>
> /* Update the link, but return if there
> * was an error */
> err = genphy_update_link(phydev);
> if (err)
> return err;
> )
> phydev->duplex = DUPLEX_FULL;
> else
> phydev->duplex = DUPLEX_HALF;
>
> status = status & MII_M1011_PHY_STATUS_SPD_MASK;
> phydev->pause = phydev->asym_pause = 0;
>
> switch (status) {
> case MII_M1011_PHY_STATUS_1000:
> phydev->speed = SPEED_1000;
> break;
>
> case MII_M1011_PHY_STATUS_100:
> phydev->speed = SPEED_100;
> break;
>
> default:
> phydev->speed = SPEED_10;
>
> break;
> }
>
> if (phydev->duplex == DUPLEX_FULL) {
> phydev->pause = lpa & LPA_PAUSE_CAP ? 1 : 0;
> phydev->asym_pause = lpa & LPA_PAUSE_ASYM ? 1 : 0;
> }
> } else {
> int bmcr = phy_read(phydev, MII_BMCR);
>
> if (bmcr < 0)
> return bmcr;
>
> if (bmcr & BMCR_FULLDPLX)
> phydev->duplex = DUPLEX_FULL;
> else
> phydev->duplex = DUPLEX_HALF;
>
> if (bmcr & BMCR_SPEED1000)
> phydev->speed = SPEED_1000;
> else if (bmcr & BMCR_SPEED100)
> phydev->speed = SPEED_100;
> else
> phydev->speed = SPEED_10;
>
> phydev->pause = phydev->asym_pause = 0;
> phydev->lp_advertising = 0;
> }
>
> return 0;
> }
>
>
--
Murali Karicheri
Linux Kernel, Keystone
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