Re: [PATCH net v2 2/6] net: stmmac: selftests: Validate EEE based on the actual LPI timer value

Hi Maxime,

Sorry for the noise, but after having a second look, there is something
which I think should be discussed at least.

On 10.9.2026 17:13, Maxime Chevallier wrote:

The EEE selftest is a 2-step test :
 - It validates that we enter in LPI mode with the
   irq_tx_path_in_lpi_mode_n counter
 - It then validates that we exit LPI when sending a frame, with the
   irq_tx_path_exit_lpi_mode_n counter.

The current state of the test lacks 2 main things :

 - We don't know exactly when was the previous frame sent (it's from 
the
   previous selftest)

 - The timeout is hardcoded, while the LPI is entered after a
   user-configurable delay. On top of that, the timeout loop uses a
   pre-decrement iterator (--retries) that actually only iterate nine
   times, so 900ms while the default LPI value is 1 second.

Let's therefore make it more deterministic :

 - Send a frame at the beginning of the test
 - Wait for more than the lpi timer value, we timeout after about twice
   the value,
 - Then send another frame, and verify that we do go out of LPI, also
   with a timeout.

Note that the test's goal isn't to validate the LPI timer value itself,
only that we enter/leave LPI mode.

Fixes: 091810dbded9 ("net: stmmac: Introduce selftests support")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
[...]

+	max_duration = usecs_to_jiffies(2 * priv->tx_lpi_timer);

tx_lpi_timer comes direct from ethtool as an unvalidated u32. So if a 
(arguable privileged
user) does 'ethtool --set-eee eth0 tx-lpi-timer 1000000000', the code 
will sleep ~2000 seconds
under rtnl_lock. Tge old code capped it at 900 ms regardless of the 
timer.

Thus I think we should clamp it at some sane value. Feel free to keep my 
R-b with the clamp.

[...]

Regards,
Nicolai