Re: umb0 broke in 6.9

On 6/14/2021 4:54 PM, Stuart Henderson wrote:

> find when the problem started .. with 6.9 userland you can probably get
> away with just booting the relevant older kernel for a test for probably
> most/maybe all of the way back to 6.8.

So I booted the 6.8 kernel, and everything seemed to be mostly working,
but the umb interface still wasn't initialized properly :(. I was
thinking I'd have to do a fresh install of 6.8 and start the test from
there, but then I considered that one thing I still hadn't done was a
cold power cycle. I have a remote console on the serial port of the
system, but it doesn't have built-in remote power control and it's not
hooked up to a remote control power switch, so it's not that convenient
to deal with power.

I coordinated a cold power cycle and booted up the 6.8 kernel, and the
umb interface worked :). I then booted the 6.9 kernel, and it also
worked? By default the kernel allocates the device to the umsm driver
(it would be nice if the umb driver took priority instead), so the first
6.9 boot after the install used that driver until I disabled it and
rebooted. I thought perhaps the 6.9 version of that driver put the card
in a bad state, so I tried booting the 6.9 kernel with it enabled, and
then booting it again with it disabled. But the umb interface was still
working after that test.

So it seems that somehow the upgrade process put the hardware in a bad
state where it would not initialize, and a cold power cycle seems to
have sorted that out. I wasn't able to reproduce the issue doing some
testing, so I guess I will write it off as "that's odd" and just be
happy it seems to be working reliably now :).

Thanks much for your assistance looking at it…