[RFC PATCH net v2 0/3] Fix OdroidC2 Gigabit Tx link issue

[jbrunet@baylibre.com (Jerome Brunet)]

On Thu, 2016-11-24 at 15:40 +0100, Martin Blumenstingl wrote:
> Hi Jerome,
> 
> On Mon, Nov 21, 2016 at 4:35 PM, Jerome Brunet <jbrunet@baylibre.com>
> wrote:
> > 
> > This patchset fixes an issue with the OdroidC2 board (DWMAC +
> > RTL8211F).
> > Initially reported as a low Tx throughput issue at gigabit speed,
> > the
> > platform enters LPI too often. This eventually break the link (both
> > Tx
> > and Rx), and require to bring the interface down and up again to
> > get the
> > Rx path working again.
> > 
> > The root cause of this issue is not fully understood yet but
> > disabling EEE
> > advertisement on the PHY prevent this feature to be negotiated.
> > With this change, the link is stable and reliable, with the
> > expected
> > throughput performance.
> I have just sent a series which allows configuring the TX delay on
> the
> MAC (dwmac-meson8b glue) side: [0]
> Disabling the TX delay generated by the MAC fixes TX throughput for
> me, even when leaving EEE enabled in the RTL8211F PHY driver!
> 
> Unfortunately the RTL8211F PHY is a black-box for the community
> because there is no public datasheeet available.
> *maybe* (pure speculation!) they're enabling the TX delay based on
> some internal magic only when EEE is enabled.

Hi already tried acting on the register setting the TX_delay. I also
tried on the PHY. I never been able to improve situation on the
Odroic2. Only disabling EEE improved the situation.

To make sure, i tried again with your patch but the result remains
unchanged. With Tx_delay disabled (either the mac or the phy), the
situation is even worse, it seems that nothing gets through

> 
> Jerome, could you please re-test the behavior on your Odroid-C2 when
> you have EEE still enabled but the TX-delay disabled?
> In my case throughput is fine, and "$ ethtool -S eth0 | grep lpi"
> gives:
> ????irq_tx_path_in_lpi_mode_n: 0
> ????irq_tx_path_exit_lpi_mode_n: 0
> ????irq_rx_path_in_lpi_mode_n: 0
> ????irq_rx_path_exit_lpi_mode_n: 0
> 

I still have lpi interrupts on my side. I don't get how a properly
configured tx_delay would disable EEE. I must be missing something
here.

> 
> Regards,
> Martin
> 
> 
> [0] http://lists.infradead.org/pipermail/linux-amlogic/2016-November/
> 001674.html