[PATCH net] net: sfp: fix state loss when updating state_hw_mask

[PATCH net] net: sfp: fix state loss when updating state_hw_mask

[Russell King (Oracle)]

Andrew reports that the SFF modules on one of the ZII platforms do not
indicate link up due to the SFP code believing that LOS indicating that
there is no signal being received from the remote end, but in fact the
LOS signal is showing that there is signal.

What makes SFF modules different from SFPs is they typically have an
inverted LOS, which uncovered this issue. When we read the hardware
state, we mask it with state_hw_mask so we ignore anything we're not
interested in. However, we don't re-read when state_hw_mask changes,
leading to sfp->state being stale.

Arrange for a software poll of the module state after we have parsed
the EEPROM in sfp_sm_mod_probe() and updated state_*_mask. This will
generate any necessary events for signal changes for the state
machine as well as updating sfp->state.

Reported-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 8475c4b70b04 ("net: sfp: re-implement soft state polling setup")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/phy/sfp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index c02cad6478a8..fb98db61e06c 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -2190,6 +2190,11 @@ static void sfp_sm_module(struct sfp *sfp, unsigned int event)
 			break;
 		}
 
+		/* Force a poll to re-read the hardware signal state after
+		 * sfp_sm_mod_probe() changed state_hw_mask.
+		 */
+		mod_delayed_work(system_wq, &sfp->poll, 1);
+
 		err = sfp_hwmon_insert(sfp);
 		if (err)
 			dev_warn(sfp->dev, "hwmon probe failed: %pe\n",
-- 
2.30.2

Re: [PATCH net] net: sfp: fix state loss when updating state_hw_mask

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri, 17 Mar 2023 07:28:00 +0000 you wrote:
> Andrew reports that the SFF modules on one of the ZII platforms do not
> indicate link up due to the SFP code believing that LOS indicating that
> there is no signal being received from the remote end, but in fact the
> LOS signal is showing that there is signal.
> 
> What makes SFF modules different from SFPs is they typically have an
> inverted LOS, which uncovered this issue. When we read the hardware
> state, we mask it with state_hw_mask so we ignore anything we're not
> interested in. However, we don't re-read when state_hw_mask changes,
> leading to sfp->state being stale.
> 
> [...]

Here is the summary with links:
  - [net] net: sfp: fix state loss when updating state_hw_mask
    https://git.kernel.org/netdev/net/c/04361b8bb818

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net] net: sfp: fix state loss when updating state_hw_mask

[Andrew Lunn]

On Sun, Mar 19, 2023 at 11:10:16AM +0000, patchwork-bot+netdevbpf@kernel.org wrote:
> Hello:
> 
> This patch was applied to netdev/net.git (main)
> by David S. Miller <davem@davemloft.net>:
> 
> On Fri, 17 Mar 2023 07:28:00 +0000 you wrote:
> > Andrew reports that the SFF modules on one of the ZII platforms do not
> > indicate link up due to the SFP code believing that LOS indicating that
> > there is no signal being received from the remote end, but in fact the
> > LOS signal is showing that there is signal.
> > 
> > What makes SFF modules different from SFPs is they typically have an
> > inverted LOS, which uncovered this issue. When we read the hardware
> > state, we mask it with state_hw_mask so we ignore anything we're not
> > interested in. However, we don't re-read when state_hw_mask changes,
> > leading to sfp->state being stale.
> > 
> > [...]
> 
> Here is the summary with links:
>   - [net] net: sfp: fix state loss when updating state_hw_mask
>     https://git.kernel.org/netdev/net/c/04361b8bb818

Hi David

This patch was submitted to net, and we can see it was also merged to
netdev/net.git. The Fixes tag of 8475c4b70b04 indicates the problem
was introduced in v6.1-rc1. Yet this fix does not appear in v6.1.31.

Do you have any idea why it has not been backported? It does cleanly
cherry-pick.

Thanks
	Andrew