Micrel Phy - Is there a way to configure the Phy not to do 802.3x flow control?

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?

Quoted 7 lines · Murali Karicheri

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?

Hi Murali

Have you played with:

ethtool -a|--show-pause devname

ethtool -A|--pause devname [autoneg on|off] [rx on|off] [tx on|off]

Andrew

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?

Quoted 7 lines · Murali Karicheri

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.

As Andrew indicated the proper way to do this is do to use ethtool if you need to this dynamically.

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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);

phy_start()

Now in hndlr() I have pause = 1, asym_pause = 1, in phy_device ptr. How can I tell the phy not to advertise initially?

Quoted 21 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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?

Quoted 3 lines

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.

Quoted 4 lines

phy_start()

Now in hndlr() I have pause = 1, asym_pause = 1, in phy_device ptr. How can I tell the phy not to advertise initially?

Quoted 24 lines · Florian Fainelli

Quoted 23 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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.

Quoted 7 lines

Quoted 1 line

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.

Murali

Quoted 4 lines

Quoted 4 lines

phy_start()

Now in hndlr() I have pause = 1, asym_pause = 1, in phy_device ptr. How can I tell the phy not to advertise initially?

Quoted 24 lines · Florian Fainelli

Quoted 23 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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.

Quoted 7 lines

Quoted 1 line

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.

Murali

Quoted 4 lines

Quoted 4 lines

phy_start()

Now in hndlr() I have pause = 1, asym_pause = 1, in phy_device ptr. How can I tell the phy not to advertise initially?

Quoted 25 lines · Murali Karicheri

Quoted 24 lines · Florian Fainelli

Quoted 23 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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.

Quoted 9 lines

Quoted 7 lines

Quoted 1 line

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.

drivers/net/phy/phy_device.c +0 -0

index d551df6..55412ad 100644

Could you explain, why the common maximum capability is not reported to the driver as per standard?? Or Am I understood it wrong?

Quoted 68 lines · Murali Karicheri

Quoted 25 lines · Murali Karicheri

Quoted 24 lines · Florian Fainelli

Quoted 23 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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.

Quoted 9 lines

Quoted 7 lines

Quoted 1 line

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.

drivers/net/phy/phy_device.c +0 -0

index d551df6..55412ad 100644

drivers/net/phy/phy_device.c int genphy_read_status(struct phy_device *phydev) · line 1025

Quoted 7 lines

drivers/net/phy/phy_device.c +2 -2

@@ -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.

Quoted 1 line

Quoted 2 lines

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?

Quoted 96 lines · Florian Fainelli

Quoted 68 lines · Murali Karicheri

Quoted 25 lines · Murali Karicheri

Quoted 24 lines · Florian Fainelli

Quoted 23 lines · Murali Karicheri

Quoted 9 lines · Florian Fainelli

Quoted 7 lines · Murali Karicheri

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?

Quoted 5 lines

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.

Quoted 9 lines

Quoted 7 lines

Quoted 1 line

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.

drivers/net/phy/phy_device.c +0 -0

index d551df6..55412ad 100644

drivers/net/phy/phy_device.c int genphy_read_status(struct phy_device *phydev) · line 1025

Quoted 7 lines

drivers/net/phy/phy_device.c +2 -2

@@ -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.

Quoted 1 line

Quoted 6 lines

Quoted 2 lines

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.

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;
}

Quoted 1 line

What it means before your patch is that flow control is reported to

the

Quoted 1 line

PHY device if the link partner advertises that, with your patch

applied,

Quoted 1 line

it is reported only if the link partner and yourself advertise flow

control.

Quoted 3 lines

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

Quoted 1 line

pause capability, which I am not convinced is correct here, because

we

Quoted 2 lines

need to take into account the user-configured pause configuration as well. Your adjust_link function should be the one deciding whether

pause

Quoted 5 lines

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

Quoted 1 line

we should probably be consolidating the pause frame behavior in

PHYLIB

Quoted 1 line

as opposed to letting drivers deal with like e.g: gianfar,

bcm63xx_enet,

Quoted 4 lines

tg3 etc.

Quoted 2 lines

Could you explain, why the common maximum capability is not reported

to the

Quoted 3 lines

Quoted 1 line

driver as per standard?? Or Am I understood it wrong?

I do not understand the question, what is "maximum capability" in

that

Quoted 2 lines

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.

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