Re: [PATCH 01/20] net: phy: realtek: Fix events detection failure in LPI mode

Hi Andrew,

I honestly tried to find any doc with a glimpse of errata for RTL8211E
PHY, but with no luck. Official datasheet didn't have any info regarding
possible hw bugs too. Thus I had no choice but to find a fix of the
problem myself.

It took me some time to figure out why the events weren't reported after
the very first link setup (turned out only a full HW reset clears the
PC1R.10 bit state). I thought it could have been connected with some
sleep/idle/power-safe mode. So I disabled the EEE initialization in the
STMMAC driver. It worked. Then I left the EEE mode enabled, but called the
phy_init_eee(phy, 0) method with "clk_stop_enable==0", so PHY wouldn't
stop RXC in LPI mode. And it wonderfully worked. Then I started to dig in
from another side. I left "RXC disable in LPI" mode enabled and tried to
figure out what was going on with the PHY when it stopped reporting events
just by reading from its CSR using phytool utility. It was curious to
discover that any attempt to read from any PHY register caused the problem
disappearance (LED2 started blinking, events got to be reported). Since I
did nothing but a mere reading from a random even EEE-unrelated register I
inferred that the problem must be in some HW/PHY bug. That's how I've got
to the patch introduced here. If you have any better idea what could be a
reason of that weird behavior I'd be glad to test it out on my device.

It is a reasonable explanation, and a read should not do any harm.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew
   

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel