On Fri, Jan 10, 2020 at 03:02:51PM +0000, ѽ҉ᶬḳ℠ wrote:

On 10/01/2020 12:53, Russell King - ARM Linux admin wrote:

quoted

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Which is also indicating everything is correct.  When the problem
occurs, check the state of the signals again as close as possible
to the event - it depends how long the transceiver keeps it
asserted.  You will probably find tx-fault is indicating
"in  hi IRQ".

just discovered userland - gpioinfo pca9538 - which seems more verbose

gpiochip2 - 8 lines:
         line   0:      unnamed   "tx-fault"   input  active-high [used]
         line   1:      unnamed "tx-disable"  output  active-high [used]
         line   2:      unnamed "rate-select0" input active-high [used]
         line   3:      unnamed        "los"   input  active-high [used]
         line   4:      unnamed   "mod-def0"   input   active-low [used]
         line   5:      unnamed       unused   input  active-high
         line   6:      unnamed       unused   input  active-high
         line   7:      unnamed       unused   input  active-high

The above is depicting the current state with the module working, i.e. being
online. Will do some testing and report back, not sure yet how to keep a
close watch relating to the failure events.

However, that doesn't give the current levels of the inputs, so it's
useless for the purpose I've asked for.

Fair enough. Operational (online) state

gpiochip2: GPIOs 504-511, parent: i2c/8-0071, pca9538, can sleep:
 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

And the same remained (unchanged) during/after the events (as closely I was
able to monitor) -> module transmit fault indicated

Try:

while ! grep -A4 'tx-fault.*in  hi' /sys/kernel/debug/gpio; do :; done

which may have a better chance of catching it.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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