Options for FBSD support with LCD device - new project [[Maybe related: I2c issues on the Pi2]]

[Ian Lepore]

On Mon, 2019-03-25 at 17:48 +0100, Bernd Walter wrote:
> On Mon, Mar 25, 2019 at 11:33:32AM -0500, Karl Denninger wrote:
> > 
> > > What do you mean by an insane rate?  It's normal for the usb
> > > controller
> > > to be showing around thousands of int/sec.  Despite what seems
> > > like a
> > > high rate, even on an on rpi-b it uses under 2% cpu to service
> > > that.
> > > 
> > > root at rpi:~ # vmstat -i
> > > interrupt                        total       rate
> > > intc0,2: vchiq0                      2          0
> > > intc0,11: systimer0           10103206       1110
> > > intc0,17:-x_dwcotg0          218596055      24007
> > > intc0,28: bcm_dma0                 834          0
> > > intc0,61: iichb0                  5778          1
> > > intc0,65: uart0                   1817          0
> > > intc0,70:-dhci_bcm0                172          0
> > > Total                        228707864      25118
> > > 
> > > -- Ian
> > 
> > The story gets more odd.
> > 
> > The same *physical* unit that I saw this on last night with no I2c
> > device connected I restarted this morning -- changing NOTHING --
> > and it
> > disappeared.
> > 
> > But -- on another unit it's still there (I haven't shut down,
> > pulled
> > power and restarted that one.)
> > 
> > vmstat -i on both doesn't show anything all that odd:
> > misbehaving that's not there, and neither are the missed interrupt
> > complaints.
> > 
> > But again, last night the one that this morning is NOT misbehaving
> > WAS,
> > and was showing the exact same thing.
> > 
> > So this looks like something that is not being initialized property
> > at
> > boot time, and sometimes however it comes up causes trouble, and
> > other
> > times it does not -- which is likely to make it a "lot" of fun to
> > find.
> 
> By causing trouble - do you mean it doesn't work?
> I noticed that my system has this message:
> nxprtc0: RTC clock not running
> Warning: bad time from time-of-day clock, system time will not be set
> accurately
> This shouldn't happen, but I wonder if the iic communication works at
> all.
> I likely wouldn't notice if the rtc failed.
> Maybe there was an initial problem at start as you said.
> Will reboot it and see what happens.
> After a reboot the message about the rtc is gone.
> Have to wait at least a day to see if the Spurious are gone too.
> 

That's not a symptom of i2c comms failure, it's a symptom of a dead rtc
battery.  The driver has to communicate with the rtc chip to determine
that the oscillator was stopped.  After a reboot all is well, because
the rtc oscillator gets started when the time is written to the chip,
and it keeps running through a reboot and only stops on a power cycle.

-- Ian