[PATCH] ethtool: Report speed and duplex as unknown when device is runtime suspended

[PATCH] ethtool: Report speed and duplex as unknown when device is runtime suspended

[Kai-Heng Feng]

Device like igb gets runtime suspended when there's no link partner. We
can't get correct speed under that state:
$ cat /sys/class/net/enp3s0/speed
1000

In addition to that, an error can also be spotted in dmesg:
[  385.991957] igb 0000:03:00.0 enp3s0: PCIe link lost

Since device can only be runtime suspended when there's no link partner,
we can directly report the speed and duplex as unknown.

Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Aaron Brown <aaron.f.brown@intel.com>
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 net/ethtool/ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 10d929abdf6a..2ba04aa9d775 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -28,6 +28,7 @@
 #include <net/xdp_sock.h>
 #include <net/flow_offload.h>
 #include <linux/ethtool_netlink.h>
+#include <linux/pm_runtime.h>
 
 #include "common.h"
 
@@ -429,6 +430,13 @@ int __ethtool_get_link_ksettings(struct net_device *dev,
 		return -EOPNOTSUPP;
 
 	memset(link_ksettings, 0, sizeof(*link_ksettings));
+
+	if (pm_runtime_suspended(dev->dev.parent)) {
+		link_ksettings->base.duplex = DUPLEX_UNKNOWN;
+		link_ksettings->base.speed = SPEED_UNKNOWN;
+		return 0;
+	}
+
 	return dev->ethtool_ops->get_link_ksettings(dev, link_ksettings);
 }
 EXPORT_SYMBOL(__ethtool_get_link_ksettings);
-- 
2.17.1

Re: [PATCH] ethtool: Report speed and duplex as unknown when device is runtime suspended

[Florian Fainelli]

On 3/26/2020 7:45 PM, Kai-Heng Feng wrote:
> Device like igb gets runtime suspended when there's no link partner. We
> can't get correct speed under that state:
> $ cat /sys/class/net/enp3s0/speed
> 1000
> 
> In addition to that, an error can also be spotted in dmesg:
> [  385.991957] igb 0000:03:00.0 enp3s0: PCIe link lost
> 
> Since device can only be runtime suspended when there's no link partner,
> we can directly report the speed and duplex as unknown.
> 
> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Cc: Aaron Brown <aaron.f.brown@intel.com>
> Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

I would push this to the responsibility of the various drivers instead
of making this part of the standard ethtool implementation.
-- 
Florian

Re: [PATCH] ethtool: Report speed and duplex as unknown when device is runtime suspended

[Kai-Heng Feng]

> On Mar 27, 2020, at 10:56, Florian Fainelli <f.fainelli@gmail.com> wrote:
> 
> 
> 
> On 3/26/2020 7:45 PM, Kai-Heng Feng wrote:
>> Device like igb gets runtime suspended when there's no link partner. We
>> can't get correct speed under that state:
>> $ cat /sys/class/net/enp3s0/speed
>> 1000
>> 
>> In addition to that, an error can also be spotted in dmesg:
>> [  385.991957] igb 0000:03:00.0 enp3s0: PCIe link lost
>> 
>> Since device can only be runtime suspended when there's no link partner,
>> we can directly report the speed and duplex as unknown.
>> 
>> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
>> Cc: Aaron Brown <aaron.f.brown@intel.com>
>> Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> 
> I would push this to the responsibility of the various drivers instead
> of making this part of the standard ethtool implementation.

My original approach [1] is to ask device to runtime resume before calling __ethtool_get_link_ksettings().
Unfortunately it will cause a deadlock if the runtime resume routine wants to hold rtnl_lock.

However, it should be totally fine (and sometimes necessary) to be able to hold rtnl_lock in runtime resume routine as Alexander explained [2].
As suggested, this patch handles the situation directly in __ethtool_get_link_ksettings().

[1] https://lore.kernel.org/lkml/20200207101005.4454-2-kai.heng.feng@canonical.com/
[2] https://lkml.org/lkml/2020/3/26/989

Kai-Heng

> -- 
> Florian