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Date: Wed, 08 Mar 2023 19:34:40 +0100
From: Klaus Kudielka <klaus.kudielka@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Michael Walle <michael@...le.cc>,
Heiner Kallweit <hkallweit1@...il.com>,
Russell King <linux@...linux.org.uk>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Felix Fietkau <nbd@....name>,
John Crispin <john@...ozen.org>,
Sean Wang <sean.wang@...iatek.com>,
Mark Lee <Mark-MC.Lee@...iatek.com>,
Lorenzo Bianconi <lorenzo@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Bryan Whitehead <bryan.whitehead@...rochip.com>,
UNGLinuxDriver@...rochip.com,
Giuseppe Cavallaro <peppe.cavallaro@...com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Jose Abreu <joabreu@...opsys.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Joel Stanley <joel@....id.au>,
Andrew Jeffery <andrew@...id.au>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org,
linux-stm32@...md-mailman.stormreply.com,
linux-aspeed@...ts.ozlabs.org,
Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH net-next v2 4/6] net: mdio: scan bus based on bus
capabilities for C22 and C45
On Tue, 2023-03-07 at 21:35 +0100, Andrew Lunn wrote:
> > Summary: Still 4 calls to mdio_bus_scan_c22, but also *2* calls to mdio_bus_scan_c45, approx. 190*100 reads by the switch driver
>
> Those calls to mdio_bus_scan_c45 are caused by 743a19e38d02 net: dsa:
> mv88e6xxx: Separate C22 and C45 transactions.
Well, yes and no. I understand orion mdio is MDIOBUS_NO_CAP
and therefore the c45 scan is *not* called until 1a136ca2e0
net: mdio: scan bus based on bus capabilities for C22 and C45.
Which is the behaviour I see.
(I needed a close look at the conditions in the if statements
that were removed then)
> The only part of a c45 scan which is not linear is
> mv88e6xxx_g2_smi_phy_wait() which is implemented by
> mv88e6xxx_wait_mask(). That loops reading a register waiting for a bit
> to change. Maybe print out the value of i, and see if it is looping
> more times for C45 than C22?
Here the debug code
diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 0a5d6c7bb1..23816cad41 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -90,6 +90,7 @@ int mv88e6xxx_wait_mask(struct mv88e6xxx_chip *chip, int addr, int reg,
u16 data;
int err;
int i;
+ static unsigned wait_count = 0, loop_count = 0;
/* There's no bus specific operation to wait for a mask. Even
* if the initial poll takes longer than 50ms, always do at
@@ -100,8 +101,13 @@ int mv88e6xxx_wait_mask(struct mv88e6xxx_chip *chip, int addr, int reg,
if (err)
return err;
- if ((data & mask) == val)
+ if ((data & mask) == val) {
+ wait_count++;
+ loop_count += i;
+ if (wait_count % 10 == 0)
+ dev_warn(chip->dev, "wait_count %u, loop_count %u\n", wait_count, loop_count);
return 0;
+ }
if (i < 2)
cpu_relax();
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 5b2f48c09a..19fde21cae 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -569,6 +569,7 @@ static int mdiobus_scan_bus_c22(struct mii_bus *bus)
{
int i;
+ dev_warn(&bus->dev, "*** mdiobus_scan_bus_c22 call ***\n");
for (i = 0; i < PHY_MAX_ADDR; i++) {
if ((bus->phy_mask & BIT(i)) == 0) {
struct phy_device *phydev;
@@ -578,6 +579,7 @@ static int mdiobus_scan_bus_c22(struct mii_bus *bus)
return PTR_ERR(phydev);
}
}
+ dev_warn(&bus->dev, "*** mdiobus_scan_bus_c22 return ***\n");
return 0;
}
@@ -585,6 +587,7 @@ static int mdiobus_scan_bus_c45(struct mii_bus *bus)
{
int i;
+ dev_warn(&bus->dev, "*** mdiobus_scan_bus_c45 call ***\n");
for (i = 0; i < PHY_MAX_ADDR; i++) {
if ((bus->phy_mask & BIT(i)) == 0) {
struct phy_device *phydev;
@@ -598,6 +601,7 @@ static int mdiobus_scan_bus_c45(struct mii_bus *bus)
return PTR_ERR(phydev);
}
}
+ dev_warn(&bus->dev, "*** mdiobus_scan_bus_c45 return ***\n");
return 0;
}
And here the trimmed results from boot @ 1a136ca2e0, plus debug code.
It's not only the looping during the mv88e6xxx_wait_mask calls, but
also the sheer amount of mv88e6xxx_wait_mask calls during the c45 scans.
(c22: ~0.1 sec & ~150 calls, c45: 2.3-2.5 sec & ~4800 calls)
[ 0.195215] mdio_bus fixed-0: *** mdiobus_scan_bus_c22 call ***
[ 0.195221] mdio_bus fixed-0: *** mdiobus_scan_bus_c22 return ***
[ 0.195617] mdio_bus f1072004.mdio-mii: *** mdiobus_scan_bus_c22 call ***
[ 0.195623] mdio_bus f1072004.mdio-mii: *** mdiobus_scan_bus_c22 return ***
[ 0.202583] mv88e6085 f1072004.mdio-mii:10: switch 0x1760 detected: Marvell 88E6176, revision 1
[ 0.212708] mdio_bus mv88e6xxx-0: *** mdiobus_scan_bus_c22 call ***
[ 0.222200] mv88e6085 f1072004.mdio-mii:10: wait_count 10, loop_count 3
........
[ 0.315724] mv88e6085 f1072004.mdio-mii:10: wait_count 150, loop_count 76
[ 0.315908] mdio_bus mv88e6xxx-0: *** mdiobus_scan_bus_c22 return ***
[ 0.315913] mdio_bus mv88e6xxx-0: *** mdiobus_scan_bus_c45 call ***
[ 0.321095] mv88e6085 f1072004.mdio-mii:10: wait_count 160, loop_count 83
........
[ 2.610380] mv88e6085 f1072004.mdio-mii:10: wait_count 4980, loop_count 1571
[ 2.613258] mdio_bus mv88e6xxx-0: *** mdiobus_scan_bus_c45 return ***
[ 2.755785] mv88e6085 f1072004.mdio-mii:10: switch 0x1760 detected: Marvell 88E6176, revision 1
[ 2.766047] mdio_bus mv88e6xxx-1: *** mdiobus_scan_bus_c22 call ***
[ 2.766960] mv88e6085 f1072004.mdio-mii:10: wait_count 4990, loop_count 1574
........
[ 2.867107] mv88e6085 f1072004.mdio-mii:10: wait_count 5130, loop_count 1645
[ 2.869938] mdio_bus mv88e6xxx-1: *** mdiobus_scan_bus_c22 return ***
[ 2.869943] mdio_bus mv88e6xxx-1: *** mdiobus_scan_bus_c45 call ***
[ 2.871556] mv88e6085 f1072004.mdio-mii:10: wait_count 5140, loop_count 1649
........
[ 5.371710] mv88e6085 f1072004.mdio-mii:10: wait_count 9970, loop_count 4282
[ 5.373332] mdio_bus mv88e6xxx-1: *** mdiobus_scan_bus_c45 return ***
Best regards, Klaus
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