On 09/28/2017 11:40 AM, Pavel Machek wrote:

Hi!

On Mon 2017-09-18 20:27:13, Tristram.Ha@microchip.com wrote:

quoted

quoted

quoted

+/**
+ * Some counters do not need to be read too often because they are less

likely

quoted

+ * to increase much.
+ */

What does comment mean? Are you caching statistics, and updating
different values at different rates?

There are 34 counters.  In normal case using generic bus I/O or PCI to read them
is very quick, but the switch is mostly accessed using SPI, or even I2C.  As the SPI
access is very slow and cannot run in interrupt context I keep worrying reading
the MIB counters in a loop for 5 or more ports will prevent other critical hardware
access from executing soon enough.  These accesses can be getting 1588 PTP
timestamps and opening/closing ports.  (RSTP Conformance Test sends test traffic
to port supposed to be closed/opened after receiving specific RSTP
BPDU.)

Hmm. Ok, interesting.

I wonder how well this is going to work if userspace actively 'does
something' with the switch.

It seems to me that even if your statistics code is careful not to do
'a lot' of accesses at the same time, userspace can use other parts of
the driver to do the same, and thus cause same unwanted effects...

A few switches have a MIB snapshot feature that is implemented such that
accessing the snapshot does not hog the remainder of the switch
registers, is this something possible on KSZ switches?

Tangential: net-next is currently open, so now would be a good time to
send a revised version of your patch series to target possibly 4.15 with
an initial implementation. Please fix the cover-letter and patch
threading such that they look like the following:

[PATCH 0/X]
   [PATCH 1/X]
   [PATCH 2/X]
   etc..

Right now this shows up as separate emails/patches and this is very
annoying to follow as a thread.

Thank you
-- 
Florian