diff mbox series

[net-next,v6,5/8] net: phy: Immediately call adjust_link if only tx_lpi_enabled changes

Message ID 20240223094425.691209-6-o.rempel@pengutronix.de
State New
Headers
Series net: ethernet: Rework EEE |

Commit Message

Oleksij Rempel Feb. 23, 2024, 9:44 a.m. UTC 
  From: Andrew Lunn <andrew@lunn.ch>

The MAC driver changes its EEE hardware configuration in its
adjust_link callback. This is called when auto-neg
completes. Disabling EEE via eee_enabled false will trigger an
autoneg, and as a result the adjust_link callback will be called with
phydev->enable_tx_lpi set to false. Similarly, eee_enabled set to true
and with a change of advertised link modes will result in a new
autoneg, and a call the adjust_link call.

If set_eee is called with only a change to tx_lpi_enabled which does
not trigger an auto-neg, it is necessary to call the adjust_link
callback so that the MAC is reconfigured to take this change into
account.

When setting phydev->enable_tx_lpi, take both eee_enabled and
tx_lpi_enabled into account, so the MAC drivers just needs to act on
phydev->enable_tx_lpi and not the whole EEE configuration.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
v7: remove ' comment and parenthesis or return
---
 drivers/net/phy/phy-c45.c | 11 ++++++++---
 drivers/net/phy/phy.c     | 25 ++++++++++++++++++++++---
 2 files changed, 30 insertions(+), 6 deletions(-)

Comments

Andrew Lunn Feb. 23, 2024, 1:17 p.m. UTC | #1 
On Fri, Feb 23, 2024 at 10:38:20AM +0000, Russell King (Oracle) wrote:
> On Fri, Feb 23, 2024 at 10:44:22AM +0100, Oleksij Rempel wrote:
> > +static void phy_ethtool_set_eee_noneg(struct phy_device *phydev,
> > +				      struct ethtool_keee *data)
> > +{
> > +	if (phydev->eee_cfg.tx_lpi_enabled !=
> > +	    data->tx_lpi_enabled) {
> > +		eee_to_eeecfg(data, &phydev->eee_cfg);
> > +		phydev->enable_tx_lpi = eeecfg_mac_can_tx_lpi(&phydev->eee_cfg);
> > +		if (phydev->link)
> > +			phy_link_up(phydev);
> 
> I'm not convinced this is a good idea. Hasn't phylib previously had
> the guarantee that the link will go down between two link-up events?
> So calling phy_link_up() may result in either the MAC driver ignoring
> it, or modifying registers that are only supposed to be modified while
> the MAC side is down.

When auto-neg is used, we expect the link to go down and come back up
again.

Here we are dealing with the case that autoneg is not used. The MAC
needs informing somehow. If we want to preserve the down/up, we could
call phy_link_down() and then phy_link_up() back to back.

     Andrew
Andrew Lunn Feb. 26, 2024, 4:44 p.m. UTC | #2 
On Sat, Feb 24, 2024 at 06:57:12PM +0100, Oleksij Rempel wrote:
> On Fri, Feb 23, 2024 at 09:53:06AM -0800, Florian Fainelli wrote:
> > On 2/23/24 05:26, Russell King (Oracle) wrote:
> > > On Fri, Feb 23, 2024 at 02:17:59PM +0100, Andrew Lunn wrote:
> > > > On Fri, Feb 23, 2024 at 10:38:20AM +0000, Russell King (Oracle) wrote:
> > > > > On Fri, Feb 23, 2024 at 10:44:22AM +0100, Oleksij Rempel wrote:
> > > > > > +static void phy_ethtool_set_eee_noneg(struct phy_device *phydev,
> > > > > > +				      struct ethtool_keee *data)
> > > > > > +{
> > > > > > +	if (phydev->eee_cfg.tx_lpi_enabled !=
> > > > > > +	    data->tx_lpi_enabled) {
> > > > > > +		eee_to_eeecfg(data, &phydev->eee_cfg);
> > > > > > +		phydev->enable_tx_lpi = eeecfg_mac_can_tx_lpi(&phydev->eee_cfg);
> > > > > > +		if (phydev->link)
> > > > > > +			phy_link_up(phydev);
> > > > > 
> > > > > I'm not convinced this is a good idea. Hasn't phylib previously had
> > > > > the guarantee that the link will go down between two link-up events?
> > > > > So calling phy_link_up() may result in either the MAC driver ignoring
> > > > > it, or modifying registers that are only supposed to be modified while
> > > > > the MAC side is down.
> > > > 
> > > > When auto-neg is used, we expect the link to go down and come back up
> > > > again.
> > > > 
> > > > Here we are dealing with the case that autoneg is not used. The MAC
> > > > needs informing somehow. If we want to preserve the down/up, we could
> > > > call phy_link_down() and then phy_link_up() back to back.
> > > 
> > > Would it be better to have a separate callback for EEE state (as I
> > > mentioned in another comment on this series?) That would be better
> > > for future SmartEEE support.
> > 
> > That sounds like a good approach to me. The additional callback also helps
> > figure out which drivers use the API and it should be simpler to audit for
> > changes in the future, too.
> 
> At this point I need help to understand how to proceed.
> What exactly do you have in mind? Some description like following would
> be helpful:
> Add callback with name phy_link_set_eee(), which should be executed in
> function bla/blup..

When i first did this patchset, SmartEEE was out of scope. One
question we should decide is, is it still out of scope, and we should
first get 'dumb' EEE fixed everywhere, and than come back and look at
SmartEEE? Or do we want to consider SmartEEE now?

The idea of this patchset was to push as much as possible down into
phylib. The MAC needs to say it supports EEE. I left handling of the
tx_lpi_timer to the MAC driver, because the PHY has nothing it can do
with that value. phylib then just needs to tell the MAC to enable or
disable EEE when autoneg has completed. That i made part of the adjust
link callback because that is the only callback we have, and most
developers seem to understand it, and the locking around it. However,
it does get messy when EEE can change without an auto-neg, as pointed
out here.

If we are leaving SmartEEE out of scope for the moment, i would say
just doing a down/up is sufficient, lets get this merged and all
'dumb' EEE fixed.

If we want feature creep and to think about SmartEEE then we need a
few changes in the overall design.

We need to make eee_get and eee_set transparent to the MAC driver,
since the PHY could be doing it all. So phylib needs to track
tx_lpi_timer. If the MAC driver indicates it can do 'dumb' EEE we
probably want to use that in preference to SmartEEE, since i guess the
MAC can also save a little power in LPI mode. So the adjust link
callback needs to say: Enable MAC EEE with this value of tx_lpi_timer,
or turn off MAC EEE. When using SmartEEE it will never actually do
either.

The current phylib model is that adjust_link is the only callback, and
the MAC driver peeks into phydev to find what it needs. I would
probably stick to that model, and not add MAC callbacks. phylink is
slightly different, mac_link_up() passes everything the MAC needs to
know as parameters, so one of my patches adds an extra parameter to
indicate if EEE should be enabled or disabled. That would need
extending with the tx_lpi_timer value.

	  Andrew
Andrew Lunn Feb. 26, 2024, 6:59 p.m. UTC | #3 
On Mon, Feb 26, 2024 at 05:53:31PM +0000, Russell King (Oracle) wrote:
> On Mon, Feb 26, 2024 at 09:50:02AM -0800, Florian Fainelli wrote:
> > This is the source of the concern, we don't know which MAC drivers we might
> > end-up breaking by calling adjust_link(link == 1) twice in a row, hopefully
> > none, because they should be well written to only update the parameters that
> > need updating, but who knows?
> 
> Just quickly... There are some (I went through a bunch.) They don't
> support EEE. I haven't been through all though, so there could be
> some which support EEE and where adjust_link() with phydev->link=true
> twice in a row could result in badness.

So i think we all agree the MAC needs to see a down/up, even if the
link itself never went down. Anything else is too risky and will
probably break something somewhere.

	 Andrew
Andrew Lunn Feb. 27, 2024, 4:12 p.m. UTC | #4 
On Tue, Feb 27, 2024 at 06:35:38AM +0100, Oleksij Rempel wrote:
> On Mon, Feb 26, 2024 at 07:59:28PM +0100, Andrew Lunn wrote:
> > On Mon, Feb 26, 2024 at 05:53:31PM +0000, Russell King (Oracle) wrote:
> > > On Mon, Feb 26, 2024 at 09:50:02AM -0800, Florian Fainelli wrote:
> > > > This is the source of the concern, we don't know which MAC drivers we might
> > > > end-up breaking by calling adjust_link(link == 1) twice in a row, hopefully
> > > > none, because they should be well written to only update the parameters that
> > > > need updating, but who knows?
> > > 
> > > Just quickly... There are some (I went through a bunch.) They don't
> > > support EEE. I haven't been through all though, so there could be
> > > some which support EEE and where adjust_link() with phydev->link=true
> > > twice in a row could result in badness.
> > 
> > So i think we all agree the MAC needs to see a down/up, even if the
> > link itself never went down. Anything else is too risky and will
> > probably break something somewhere.
> 
> Means, this patch should be dropped.

No.

This patch handles the case that EEE is changed, but does not require
an auto-neg cycle. If you drop this patch, that use case breaks.

You need to extend this patch to signal to the MAC a down followed by
an up. It is a fake down, the media side never goes down, but the MAC
needs to think it has in order to keep with the usual convention that
we never call adjust_link() twice with phydev->link not changing.

   Andrew
diff mbox series

Patch

diff --git a/drivers/net/phy/phy-c45.c b/drivers/net/phy/phy-c45.c
index fa5145c9328e..f98600ed3b35 100644
--- a/drivers/net/phy/phy-c45.c
+++ b/drivers/net/phy/phy-c45.c
@@ -1550,6 +1550,8 @@  EXPORT_SYMBOL(genphy_c45_ethtool_get_eee);
  * advertised, but the previously advertised link modes are
  * retained. This allows EEE to be enabled/disabled in a
  * non-destructive way.
+ * Returns either error code, 0 if there was no change, or positive
+ * value if there was a change which triggered auto-neg.
  */
 int genphy_c45_ethtool_set_eee(struct phy_device *phydev,
 			       struct ethtool_keee *data)
@@ -1581,9 +1583,12 @@  int genphy_c45_ethtool_set_eee(struct phy_device *phydev,
 	ret = genphy_c45_an_config_eee_aneg(phydev);
 	if (ret < 0)
 		return ret;
-	if (ret > 0)
-		return phy_restart_aneg(phydev);
-
+	if (ret > 0) {
+		ret = phy_restart_aneg(phydev);
+		if (ret < 0)
+			return ret;
+		return 1;
+	}
 	return 0;
 }
 EXPORT_SYMBOL(genphy_c45_ethtool_set_eee);
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index f0ed07c74a36..9e26508d5a31 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -988,7 +988,8 @@  static int phy_check_link_status(struct phy_device *phydev)
 		if (err < 0)
 			phydev->enable_tx_lpi = false;
 		else
-			phydev->enable_tx_lpi = !!err;
+			phydev->enable_tx_lpi = (err & phydev->eee_cfg.tx_lpi_enabled);
+
 		phy_link_up(phydev);
 	} else if (!phydev->link && phydev->state != PHY_NOLINK) {
 		phydev->state = PHY_NOLINK;
@@ -1679,6 +1680,21 @@  int phy_ethtool_get_eee(struct phy_device *phydev, struct ethtool_keee *data)
 }
 EXPORT_SYMBOL(phy_ethtool_get_eee);
 
+/* auto-neg not triggered, directly inform the MAC if something
+ * changed
+ */
+static void phy_ethtool_set_eee_noneg(struct phy_device *phydev,
+				      struct ethtool_keee *data)
+{
+	if (phydev->eee_cfg.tx_lpi_enabled !=
+	    data->tx_lpi_enabled) {
+		eee_to_eeecfg(data, &phydev->eee_cfg);
+		phydev->enable_tx_lpi = eeecfg_mac_can_tx_lpi(&phydev->eee_cfg);
+		if (phydev->link)
+			phy_link_up(phydev);
+	}
+}
+
 /**
  * phy_ethtool_set_eee - set EEE supported and status
  * @phydev: target phy_device struct
@@ -1695,11 +1711,14 @@  int phy_ethtool_set_eee(struct phy_device *phydev, struct ethtool_keee *data)
 
 	mutex_lock(&phydev->lock);
 	ret = genphy_c45_ethtool_set_eee(phydev, data);
-	if (!ret)
+	if (ret >= 0) {
+		if (ret == 0)
+			phy_ethtool_set_eee_noneg(phydev, data);
 		eee_to_eeecfg(data, &phydev->eee_cfg);
+	}
 	mutex_unlock(&phydev->lock);
 
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 EXPORT_SYMBOL(phy_ethtool_set_eee);