Re: [PATCH net-next v2 01/10] net: dsa: add debugfs interface

Andrew Lunn
2017-09-15T15:19:16Z

> > Reg cpu lan0 lan1 lan2 lan3 lan4 lan5 global0 global1
> >-----------------------------------------------------------------------------
> > 00: 4e07 4d04 4d04 4d04 4d04 4d04 4d04 0000 00000
> > 01: 403e 003d 003d 003d 003d 003d 003d 0000 00000
> > 02: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 03: 3521 3521 3521 3521 3521 3521 3521 0000 00000
> > 04: 0533 373f 373f 373f 373f 373f 373f 0000 00000
> > 05: 8000 0000 0000 0000 0000 0000 0000 0000 00000
> > 06: 005f 003f 003f 003f 003f 003f 003f 0000 00000
> > 07: 002a 002a 002a 002a 002a 002a 002a 0000 00000
> > 08: 2080 2080 2080 2080 2080 2080 2080 0000 00000
> > 09: 0001 0001 0001 0001 0001 0001 0001 0000 00000
> > 0a: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 0b: 0020 0000 0000 0000 0000 0000 0000 0000 00000
> > 0c: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 0d: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 0e: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 0f: 9100 dada dada dada dada dada dada 0000 00000
> > 10: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 11: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 12: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 13: 0000 00d8 00d8 00d8 00d8 00d8 00d8 0000 00000
> > 14: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 15: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 16: 0022 0000 0000 0000 0000 0000 0000 0000 00000
> > 17: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 18: 3210 2210 2210 2210 2210 2210 2210 0000 00000
> > 19: 7654 7654 7654 7654 7654 7654 7654 0000 00000
> > 1a: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 1b: 8000 8000 8000 8000 8000 8000 8000 0000 00000
> > 1c: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 1d: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 1e: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> > 1f: 0000 0000 0000 0000 0000 0000 0000 0000 00000
> >
>
> Is this a reg dump per-port?

No. Look at the global0 and global1 columns. These are not port
registers, but switch global registers. The other columns are per
port. We could have a two column table per port for these
registers. However for debugging, it is useful to see the port
registers side-by-side. The difference between ports often gives you
clues as to what is wrong.

The global registers however are scoped to a switch, not a port.

> you can have reg array for each. How the values can change? Is this
> change result of driver<->hw communication? If yes, you might consider
> using devlink hwmsg trace to expose the communication to userspace.

The reason a value changes varies per bit. Some are status, set by the
switch. Some are configuration, set by the driver. They are all mixed
up together. And some registers are actually just multiplexors onto
other tables of registers. You set an opcode in the lower nibble,
address in the middle, set the top bit and busy loop waiting for it to
clear. You can then read a result out of the register, or a near by
register. So the register dump gives you an idea what the last access
to such a table was.

> I would rather focus on what exactly you need to expose to userspace,
> then we can figure out how to do it. Generic multipurpose arrays should
> be considered as last-resort solution in my opinion.

So go look at Vivien's patches. That is what we want to expose. For a
start. Viviens patches are at the DSA level. Once we get something
accepted at that level, i can imaging drivers want to augment it with
driver specific tables. But we can handle that later.

Andrew