Re: [RFC PATCH 0/2] Reset PHY in fec_resume if it got powered down

On Tue, 2021-12-07 at 01:58 +0000, Joakim Zhang wrote:

Hi Philippe,

quoted

-----Original Message-----
From: Philippe Schenker <redacted>
Sent: 2021年12月6日 18:13
To: netdev@vger.kernel.org; Joakim Zhang <redacted>;
Fabio Estevam [off-list ref]; Fugang Duan
[off-list ref]; David S . Miller [off-list ref];
Russell
King [off-list ref]; Andrew Lunn [off-list ref]; Jakub
Kicinski [off-list ref]
Cc: Philippe Schenker <redacted>;
linux-kernel@vger.kernel.org
Subject: [RFC PATCH 0/2] Reset PHY in fec_resume if it got powered
down


If a hardware-design is able to control power to the Ethernet PHY
and relying
on software to do a reset, the PHY does no longer work after
resuming from
suspend, given the PHY does need a hardware-reset.
The Freescale fec driver does currently control the reset-signal of
a phy but
does not issue a reset on resume.

On Toradex Apalis iMX8 board we do have such a design where we also
don't
place the RC circuit to delay the reset-line by hardware. Hence we
fully rely
on software to do so.
Since I didn't manage to get the needed parts of Apalis iMX8 working
with
mainline this patchset was only tested on the downstream kernel
toradex_5.4-2.3.x-imx. [1] This kernel is based on NXP's release
imx_5.4.70_2.3.0. [2] The affected code is still the same on
mainline kernel,
which would actually make me comfortable merging this patch, but due
to
this fact I'm sending this as RFC maybe someone else is able to test
this code.

This patchset aims to change the behavior by resetting the ethernet
PHY in
fec_resume. A short description of the patches can be found below,
please
find a detailed description in the commit-messages of the respective
patches.

[PATCH 2/2] net: fec: reset phy in resume if it was powered down

This patch calls fec_reset_phy just after regulator enable in
fec_resume,
when the phy is resumed

[PATCH 1/2] net: fec: make fec_reset_phy not only usable once

This patch prepares the function fec_reset_phy to be called multiple
times. It
stores the data around the reset-gpio in fec_enet_private.
This patch aims to do no functional changes.

[1]
https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgit.tor
adex.com%2Fcgit%2Flinux-toradex.git%2Flog%2F%3Fh%3Dtoradex_5.4-2.3.x
-imx&amp;data=04%7C01%7Cqiangqing.zhang%40nxp.com%7Cf3c138ed9232
4a8d75e708d9b8a11b9a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%
7C637743824364193423%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAw
MDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sda
ta=Bw%2BZdqhAjPXqKJFZCXp0mtId1x9mkX6f6MW2ky6U1ww%3D&amp;res
erved=0
[2]
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsourc
e.codeaurora.org%2Fexternal%2Fimx%2Flinux-imx%2Flog%2F%3Fh%3Dimx_
5.4.70_2.3.0&amp;data=04%7C01%7Cqiangqing.zhang%40nxp.com%7Cf3c13
8ed92324a8d75e708d9b8a11b9a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C
0%7C0%7C637743824364193423%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiM
C4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000
&amp;sdata=of9z9hfVhHakVScLxCdEo%2BXmd2B9Ad9X8Rry6GjEZE4%3D&a
mp;reserved=0

In fec driver, it has supported hardware reset for PHY when MAC resume
back,

fec_resume() -> phy_init_hw() -> phy_device_reset() de-assert the
reset signal, you only need implement
the properties which PHY core provided.

I think you should not use deprecated reset properties provided by fec
driver, instead the common
reset properties provided by PHY core.

Please check the dt-bindings for more details:
Documentation/devicetree/bindings/net/fsl,fec.yaml
Documentation/devicetree/bindings/net/ethernet-phy.yaml

Best Regards,
Joakim Zhang

Hi Joakim and many thanks for that hint! I tried that out but
unfortunately it still does not work due to phy_init_hw() only
deasserting the reset. For that to work, for example a call of
phy_device_reset(ndev->phydev, 1); in fec_suspend or in fec_resume
before enabling the supply would work, in order to assert that reset.

I see now two ways to go to fix our issue:

1. Assert the phy-reset gpio in fec_suspend() or fec_resume()

2. Add support for regulators in drivers/net/phy/phy-core.c and handle
the phy-reset properly in there with assert-us and deassert-us delays.

As you probably have a much better overview: Do you see another
possibility to handle phy-reset after resuming? Or which way shall I
choose to go forward?

Thanks in advance for any advice
Philippe

quoted

Philippe Schenker (2):
  net: fec: make fec_reset_phy not only usable once
  net: fec: reset phy in resume if it was powered down

 drivers/net/ethernet/freescale/fec.h      |  6 ++
 drivers/net/ethernet/freescale/fec_main.c | 98 ++++++++++++++++----
---
 2 files changed, 73 insertions(+), 31 deletions(-)

--
2.34.0