Patchwork ucc_geth: Fix half-duplex operation for non-MII/RMII interfaces

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Submitter Anton Vorontsov
Date June 24, 2009, 5:45 p.m.
Message ID <20090624174557.GA31479@oksana.dev.rtsoft.ru>
Download mbox | patch
Permalink /patch/29140/
State Superseded
Delegated to: Kumar Gala
Headers show

Comments

Anton Vorontsov - June 24, 2009, 5:45 p.m.
Currently the half-duplex operation seems to not work reliably for
RGMII/GMII PHY interfaces. It takes about 10 minutes to boot NFS
rootfs using 10/half link, following symptoms were observed:

  ucc_geth: QE UCC Gigabit Ethernet Controller
  ucc_geth: UCC1 at 0xe0082000 (irq = 32)
  [...]
  Sending DHCP and RARP requests .
  PHY: mdio@e0082120:07 - Link is Up - 10/Half
  ., OK
  [...]
  Looking up port of RPC 100003/2 on 10.0.0.2
  Looking up port of RPC 100005/1 on 10.0.0.2
  VFS: Mounted root (nfs filesystem) readonly on device 0:13.
  Freeing unused kernel memory: 204k init
  eth0: no IPv6 routers present
  nfs: server 10.0.0.2 not responding, still trying
  nfs: server 10.0.0.2 not responding, still trying
  nfs: server 10.0.0.2 not responding, still trying
  nfs: server 10.0.0.2 OK
  nfs: server 10.0.0.2 OK
  nfs: server 10.0.0.2 not responding, still trying
  [... few minutes of OK/not responding flood ...]

The statistic shows that there are indeed some errors:

  # ethtool -S eth0 | grep -v ": 0"
  NIC statistics:
       tx-64-frames: 42
       tx-65-127-frames: 9
       tx-128-255-frames: 4768
       rx-64-frames: 41
       rx-65-127-frames: 260
       rx-128-255-frames: 2679
       tx-bytes-ok: 859634
       tx-multicast-frames: 5
       tx-broadcast-frames: 7
       rx-frames: 8333
       rx-bytes-ok: 8039364
       rx-bytes-all: 8039364
       stats-counter-mask: 4294901760
       tx-single-collision: 324
       tx-multiple-collision: 47
       tx-late-collsion: 604
       tx-aborted-frames: 604
       tx-frames-ok: 4967
       tx-256-511-frames: 3
       tx-512-1023-frames: 79
       tx-1024-1518-frames: 71
       rx-256-511-frames: 37
       rx-512-1023-frames: 73
       rx-1024-1518-frames: 5243

According to current QEIWRM (Rev. 2 5/2009), FDX bit can be 0 for
RGMII(10/100) modes, while MPC8568ERM (Rev. C 02/2007) spec says
that cleared FDX bit is permitted for MII/RMII modes only.

The symptoms above were seen on MPC8569E-MDS boards, so QEIWRM is
clearly wrong, and this patch completely cures the problems above.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
---
 drivers/net/ucc_geth.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
Mark Huth - June 25, 2009, 5:11 a.m.
Anton Vorontsov wrote:
> Currently the half-duplex operation seems to not work reliably for
> RGMII/GMII PHY interfaces. It takes about 10 minutes to boot NFS
> rootfs using 10/half link, following symptoms were observed:
> 
>   ucc_geth: QE UCC Gigabit Ethernet Controller
>   ucc_geth: UCC1 at 0xe0082000 (irq = 32)
>   [...]
>   Sending DHCP and RARP requests .
>   PHY: mdio@e0082120:07 - Link is Up - 10/Half
>   ., OK
So why does the phy think this is a half-duplex network?
>   [...]
>   Looking up port of RPC 100003/2 on 10.0.0.2
>   Looking up port of RPC 100005/1 on 10.0.0.2
>   VFS: Mounted root (nfs filesystem) readonly on device 0:13.
>   Freeing unused kernel memory: 204k init
>   eth0: no IPv6 routers present
>   nfs: server 10.0.0.2 not responding, still trying
>   nfs: server 10.0.0.2 not responding, still trying
>   nfs: server 10.0.0.2 not responding, still trying
>   nfs: server 10.0.0.2 OK
>   nfs: server 10.0.0.2 OK
>   nfs: server 10.0.0.2 not responding, still trying
>   [... few minutes of OK/not responding flood ...]
> 
> The statistic shows that there are indeed some errors:
> 
>   # ethtool -S eth0 | grep -v ": 0"
>   NIC statistics:
>        tx-64-frames: 42
>        tx-65-127-frames: 9
>        tx-128-255-frames: 4768
>        rx-64-frames: 41
>        rx-65-127-frames: 260
>        rx-128-255-frames: 2679
>        tx-bytes-ok: 859634
>        tx-multicast-frames: 5
>        tx-broadcast-frames: 7
>        rx-frames: 8333
>        rx-bytes-ok: 8039364
>        rx-bytes-all: 8039364
>        stats-counter-mask: 4294901760
>        tx-single-collision: 324
>        tx-multiple-collision: 47
>        tx-late-collsion: 604
>        tx-aborted-frames: 604
The above two counters are the actual errors from a half-duplex ethernet 
configuration.  The size of the collision domain is limited so that the 
collisions from one end will reach the other end within the minimum 
frame length wire time.  Thus the collision will be detected within the 
first 64 bytes of the frame.  A late collision indicates a 
mis-configured network. The fact that everything seems to work when the 
MAC is placed into full-duplex mode hints that the network is really a 
full-duplex network.

Otherwise, if the network is really half-duplex, then presence of a 
full-duplex node will result in the other nodes seeing CRC/framing 
errors on receive, and possibly also late collisions, as the full-duplex 
node does not observe the CS or the CD( carrier sense and collision 
detect) part of CSMA/CD, because it doesn't care.

Putting a node in full-duplex will always make the nasty collision 
related errors go away, but it may not be a proper diagnosis of the problem.
>        tx-frames-ok: 4967
>        tx-256-511-frames: 3
>        tx-512-1023-frames: 79
>        tx-1024-1518-frames: 71
>        rx-256-511-frames: 37
>        rx-512-1023-frames: 73
>        rx-1024-1518-frames: 5243
> 
> According to current QEIWRM (Rev. 2 5/2009), FDX bit can be 0 for
> RGMII(10/100) modes, while MPC8568ERM (Rev. C 02/2007) spec says
> that cleared FDX bit is permitted for MII/RMII modes only.
> 
> The symptoms above were seen on MPC8569E-MDS boards, so QEIWRM is
> clearly wrong, and this patch completely cures the problems above.

Not so fast - RGMII and GMII refer to the interface between the MAC and 
the PHY.  While Gigabit physical links will always be full-duplex, phys 
that detect lower operational modes will indicate half-duplex where 
needed, and putting the MAC into full-duplex will make other nodes see 
errors.

As Andy indicated later, it may be necessary to alter the interface 
definition in those cases, depending on the particular hardware. 
Forcing full-duplex does not seem to be a general solution.

Mark Huth
MontaVista Software
> 
> Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
> ---
>  drivers/net/ucc_geth.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
> index 464df03..e618cf2 100644
> --- a/drivers/net/ucc_geth.c
> +++ b/drivers/net/ucc_geth.c
> @@ -1469,12 +1469,16 @@ static void adjust_link(struct net_device *dev)
>  	if (phydev->link) {
>  		u32 tempval = in_be32(&ug_regs->maccfg2);
>  		u32 upsmr = in_be32(&uf_regs->upsmr);
> +		phy_interface_t phyi = ugeth->phy_interface;
> +
>  		/* Now we make sure that we can be in full duplex mode.
>  		 * If not, we operate in half-duplex mode. */
>  		if (phydev->duplex != ugeth->oldduplex) {
>  			new_state = 1;
> -			if (!(phydev->duplex))
> -				tempval &= ~(MACCFG2_FDX);
> +			if (!phydev->duplex &&
> +					(phyi == PHY_INTERFACE_MODE_MII ||
> +					 phyi == PHY_INTERFACE_MODE_RMII))
> +				tempval &= ~MACCFG2_FDX;
>  			else
>  				tempval |= MACCFG2_FDX;
>  			ugeth->oldduplex = phydev->duplex;
Anton Vorontsov - June 25, 2009, 7:02 a.m.
On Wed, Jun 24, 2009 at 10:11:14PM -0700, Mark Huth wrote:
> Anton Vorontsov wrote:
>> Currently the half-duplex operation seems to not work reliably for
>> RGMII/GMII PHY interfaces. It takes about 10 minutes to boot NFS
>> rootfs using 10/half link, following symptoms were observed:
>>
>>   ucc_geth: QE UCC Gigabit Ethernet Controller
>>   ucc_geth: UCC1 at 0xe0082000 (irq = 32)
>>   [...]
>>   Sending DHCP and RARP requests .
>>   PHY: mdio@e0082120:07 - Link is Up - 10/Half
>>   ., OK
> So why does the phy think this is a half-duplex network?

Because it's physical media now in half-duplex. At least that's
what PHY detects.

[...]
>>        tx-late-collsion: 604
>>        tx-aborted-frames: 604
> The above two counters are the actual errors from a half-duplex ethernet  
> configuration.  The size of the collision domain is limited so that the  
> collisions from one end will reach the other end within the minimum  
> frame length wire time.  Thus the collision will be detected within the  
> first 64 bytes of the frame.  A late collision indicates a  
> mis-configured network. The fact that everything seems to work when the  
> MAC is placed into full-duplex mode hints that the network is really a  
> full-duplex network.

No, it's half. Can be configured so on both sides, with or
without auto-negotiation. The "10/half" message comes from a
PHY layer, the PHY layer reports human readable values of
PHY's LPA/BMSR registers, not MAC's configuration.

Of course, it could be that the root cause of the problems
I observe is weird NIC on my host. Well, then QA team should
have used the same broken NIC on their hosts. :-)

I can easily test it by interconnecting two targets though.

> Otherwise, if the network is really half-duplex, then presence of a  
> full-duplex node will result in the other nodes seeing CRC/framing  
> errors on receive, and possibly also late collisions, as the full-duplex  
> node does not observe the CS or the CD( carrier sense and collision  
> detect) part of CSMA/CD, because it doesn't care.
>
> Putting a node in full-duplex will always make the nasty collision  
> related errors go away, but it may not be a proper diagnosis of the 
> problem.

>>        tx-frames-ok: 4967
>>        tx-256-511-frames: 3
>>        tx-512-1023-frames: 79
>>        tx-1024-1518-frames: 71
>>        rx-256-511-frames: 37
>>        rx-512-1023-frames: 73
>>        rx-1024-1518-frames: 5243
>>
>> According to current QEIWRM (Rev. 2 5/2009), FDX bit can be 0 for
>> RGMII(10/100) modes, while MPC8568ERM (Rev. C 02/2007) spec says
>> that cleared FDX bit is permitted for MII/RMII modes only.
>>
>> The symptoms above were seen on MPC8569E-MDS boards, so QEIWRM is
>> clearly wrong, and this patch completely cures the problems above.
>
> Not so fast - RGMII and GMII refer to the interface between the MAC and  
> the PHY.

Correct.

> While Gigabit physical links will always be full-duplex, phys  
> that detect lower operational modes will indicate half-duplex where  
> needed, and putting the MAC into full-duplex will make other nodes see  
> errors.

D'oh!

[1358634.636147] eth1: Transmit error, Tx status register 82.
[1358634.636150] Probably a duplex mismatch.  See Documentation/networking/vortex.txt

It's on a host side.

> As Andy indicated later, it may be necessary to alter the interface  
> definition in those cases, depending on the particular hardware. Forcing 
> full-duplex does not seem to be a general solution.

Definitely. Though I'm out of ideas if it's NOT host-side issue.

Thanks!
Anton Vorontsov - June 25, 2009, 11:17 a.m.
On Thu, Jun 25, 2009 at 11:02:36AM +0400, Anton Vorontsov wrote:
[...]
> Of course, it could be that the root cause of the problems
> I observe is weird NIC on my host. Well, then QA team should
> have used the same broken NIC on their hosts. :-)
> 
> I can easily test it by interconnecting two targets though.
[...]
> Definitely. Though I'm out of ideas if it's NOT host-side issue.

Two boards interconnected work fine. eTSEC + SKY2 NIC also work
OK. I'll test some more NICs, known to not work is 3Com
Corporation 3c905C-TX/TX-M [Tornado] (rev 74).


After some netperf tests, statistic on a gianfar board:

# ethtool -S eth0 | grep -v ": 0"
NIC statistics:
     rx-dropped-by-kernel: 2
     tx-rx-64-frames: 52
     tx-rx-65-127-frames: 20668
     tx-rx-128-255-frames: 10343
     tx-rx-256-511-frames: 113
     tx-rx-512-1023-frames: 147
     tx-rx-1024-1518-frames: 45965
     rx-bytes: 45075782
     rx-packets: 50300
     rx-carrier-sense-error: 1
     rx-fragmented-frames: 7600
     tx-byte-counter: 27401677
     tx-packets: 34618
     tx-broadcast-packets: 3
     tx-deferral-packets: 5
     tx-single-collision-packets: 4039
     tx-multiple-collision-packets: 1943
     tx-excessive-collision-packets: 30
     tx-total-collision: 785


Thanks for the ideas, Mark.

Patch

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index 464df03..e618cf2 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c
@@ -1469,12 +1469,16 @@  static void adjust_link(struct net_device *dev)
 	if (phydev->link) {
 		u32 tempval = in_be32(&ug_regs->maccfg2);
 		u32 upsmr = in_be32(&uf_regs->upsmr);
+		phy_interface_t phyi = ugeth->phy_interface;
+
 		/* Now we make sure that we can be in full duplex mode.
 		 * If not, we operate in half-duplex mode. */
 		if (phydev->duplex != ugeth->oldduplex) {
 			new_state = 1;
-			if (!(phydev->duplex))
-				tempval &= ~(MACCFG2_FDX);
+			if (!phydev->duplex &&
+					(phyi == PHY_INTERFACE_MODE_MII ||
+					 phyi == PHY_INTERFACE_MODE_RMII))
+				tempval &= ~MACCFG2_FDX;
 			else
 				tempval |= MACCFG2_FDX;
 			ugeth->oldduplex = phydev->duplex;