Re: [drivers/net/phy/sfp] intermittent failure in state machine checks
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Date: 2020-01-10 19:01:41
On Fri, Jan 10, 2020 at 06:44:18PM +0000, ѽ҉ᶬḳ℠ wrote:
On 10/01/2020 17:38, Russell King - ARM Linux admin wrote:quoted
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On Fri, Jan 10, 2020 at 04:53:06PM +0000, ѽ҉ᶬḳ℠ wrote:quoted
Seems that the debug avenue has been exhausted, short of running SFP.C in debug mode.You're saying you never see TX_FAULT asserted other than when the interface is down?Yes, it never exhibits once the iif is up - it is rock-stable in that state, only ever when being transitioned from down state to up state. Pardon, if that has not been made explicitly clear previously.I think if we were to have SFP debug enabled, you'll find that TX_FAULT is being reported to SFP as being asserted.If really necessary I could ask the TOS developers to assist, not sure whether they would oblidge. Their Master branch build bot compiles twice a day. Would it just involve setting a kernel debug flag or something more elaborate?quoted
You probably aren't running that while loop, as it will exit when it sees TX_FAULT asserted. So, here's another bit of shell code for you to run: ip li set dev eth2 down; \ ip li set dev eth2 up; \ date while :; do cat /proc/uptime while ! grep -A5 'tx-fault.*in hi' /sys/kernel/debug/gpio; do :; done cat /proc/uptime while ! grep -A5 'tx-fault.*in lo' /sys/kernel/debug/gpio; do :; done done This will give you output such as: Fri 10 Jan 17:31:06 GMT 2020 774869.13 1535859.48 gpio-509 ( |tx-fault ) in hi ... 774869.14 1535859.49 gpio-509 ( |tx-fault ) in lo ... 774869.15 1535859.50 The first date and "uptime" output is the timestamp when the interface was brought up. Subsequent "uptime" outputs can be used to calculate the time difference in seconds between the state printed immediately prior to the uptime output, and the first "uptime" output. So in the above example, the tx-fault signal was hi at 10ms, and then went low 20ms after the up.awfully nice of you to provide the code, this is the output when the iif is brought down and up again and exhibiting the transmit fault. ip li set dev eth2 down; \quoted
ip li set dev eth2 up; \ dateFri Jan 10 18:34:52 GMT 2020 root@to:~# while :; doquoted
cat /proc/uptime while ! grep -A5 'tx-fault.*in hi' /sys/kernel/debug/gpio; do :; done cat /proc/uptime while ! grep -A5 'tx-fault.*in lo' /sys/kernel/debug/gpio; do :; done done
Hmm, I missed a ; \ at the end of "date", so this isn't quite what I wanted, but it'll do. What that means is that:
1865.20 3224.67
doesn't bear the relationship that I wanted to the interface coming up.
gpio-504 ( |tx-fault ) in hi IRQ gpio-505 ( |tx-disable ) out hi gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1871.77 3230.71
TX_FAULT is high at 1871.77 and TX_DISABLE is high, so the interface is down.
gpio-504 ( |tx-fault ) in lo IRQ gpio-505 ( |tx-disable ) out lo gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1919.06 3309.55
Almost 47.3s later, TX_FAULT has gone low.
gpio-504 ( |tx-fault ) in hi IRQ gpio-505 ( |tx-disable ) out lo gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1919.07 3309.57
After 10ms, it goes high again - this will cause the first report of a transmit fault.
gpio-504 ( |tx-fault ) in lo IRQ gpio-505 ( |tx-disable ) out lo gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1920.68 3312.28
About 1.6s later, it goes low, maybe as a result of the first attempt to clear the fault by a brief pulse on TX_DISABLE. So, we wait 1s before asserting TX_DISABLE for 10us, which would have happened around 1920.07. We then have 300ms for initialisation, which would've taken us to 1920.37, so this may have been interpreted as the fault still being present. The next clearance attempt would have been scheduled for about 1921.37.
gpio-504 ( |tx-fault ) in hi IRQ gpio-505 ( |tx-disable ) out lo gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1921.86 3314.21
1.2s later, it re-asserts.
gpio-504 ( |tx-fault ) in lo IRQ gpio-505 ( |tx-disable ) out lo gpio-506 ( |rate-select0 ) in lo gpio-507 ( |los ) in lo IRQ gpio-508 ( |mod-def0 ) in lo IRQ 1921.86 3314.21
and deasserts within the same 10ms.
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However, bear in mind that even this will not be good enough to spot transitory changes on TX_FAULT - as your I2C GPIO expander is interrupt capable, watching /proc/interrupts may tell you more. If the TX_FAULT signal is as stable as you claim it is, you should see the interrupt count for it remaining the same.Once the iif is up those values remain stable indeed. cat /proc/interrupts | grep sfp 52: 0 0 pca953x 4 Edge sfp 53: 0 0 pca953x 3 Edge sfp 54: 6 0 pca953x 0 Edge sfp and only incrementing with ifupdown action (which would be logical) cat /proc/interrupts | grep sfp 52: 0 0 pca953x 4 Edge sfp 53: 0 0 pca953x 3 Edge sfp 54: 11 0 pca953x 0 Edge sfp
According to this, TX_FAULT has toggled five times. This would seem to negate your previous comment about TX_FAULT being stable. Therefore, I'd say that the SFP state machines are operating as designed, and as per the SFP MSA, and what we have is a module that likes to assert TX_FAULT for unknown reasons, and this confirms the hypothesis I've been putting forward. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up