Re: [PATCH net-next 8/8] net: stmmac: qcom-ethqos: add a DMA-reset quirk for sa8775p-ride-r3

Andrew Lunn
2024-06-20T19:30:59Z

On Thu, Jun 20, 2024 at 10:20:08AM +0200, Bartosz Golaszewski wrote:
> On Wed, Jun 19, 2024 at 9:33 PM Andrew Lunn <andrew@lunn.ch> wrote:
> >
> > On Wed, Jun 19, 2024 at 08:45:49PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > >
> > > On sa8775p-ride the RX clocks from the AQR115C PHY are not available at
> > > the time of the DMA reset so we need to loop TX clocks to RX and then
> > > disable loopback after link-up. Use the provided callbacks to do it for
> > > this board.
> >
> > How does this differ to ethqos_clks_config()?
> >
>
> I'm not sure I understand the question. This function is called at
> probe/remove and suspend/resume. It's not linked to the issue solved
> here.

/* Enable functional clock to prevent DMA reset to timeout due
* to lacking PHY clock after the hardware block has been power
* cycled. The actual configuration will be adjusted once
* ethqos_fix_mac_speed() is invoked.

It sounds similar, "DMA reset", "lacking PHY clock".

There is also

commit 58329b03a5957904fa2b33b3824ed19e7b42c9e9
Author: Romain Gantois <romain.gantois@bootlin.com>
Date: Tue Mar 26 14:32:11 2024 +0100

net: stmmac: Signal to PHY/PCS drivers to keep RX clock on

There is a reocurring issue with stmmac controllers where the MAC fails to
initialize its hardware if an RX clock signal isn't provided on the MAC/PHY
link.

This causes issues when PHY or PCS devices either go into suspend while
cutting the RX clock or do not bring the clock signal up early enough for
the MAC to initialize successfully.

Set the mac_requires_rxc flag in the stmmac phylink config so that PHY/PCS
drivers know to keep the RX clock up at all times.

It would be good to explain the big pictures, why these two changes
are not sufficient.

Andrew