Re: [PATCH net-next v1 1/1] net: phy: dp83td510: Add basic support for the DP83TD510 Ethernet PHY

Hi Andrew,

On Fri, Jul 23, 2021 at 08:12:05PM +0200, Andrew Lunn wrote:

On Fri, Jul 23, 2021 at 07:08:49PM +0200, Oleksij Rempel wrote:

quoted

Hi Andrew,

On Fri, Jul 23, 2021 at 03:22:16PM +0200, Andrew Lunn wrote:

quoted

On Fri, Jul 23, 2021 at 12:42:18PM +0200, Oleksij Rempel wrote:

quoted

The DP83TD510E is an ultra-low power Ethernet physical layer transceiver
that supports 10M single pair cable.

This driver provides basic support for this chip:
- link status
- autoneg can be turned off
- master/slave can be configured to be able to work without autoneg

This driver and PHY was tested with ASIX AX88772B USB Ethernet controller.

Hi Oleksij

There were patches flying around recently for another T1L PHY which
added new link modes. Please could you work together with that patch
to set the phydev features correctly to indicate this PHY is also a
T1L, and if it support 2.4v etc.

ACK, thx. I was not able to spend enough time to investigate all needed
caps, so I decided to go mainline with limited functionality first.

Limited functionality is fine, but what is implemented should be
correct. And from what i see in the patch, it is hard to know if the
PHYs basic features are correctly determined. What does ethtool show?
Is 100BaseT being offered? Half duplex?

With current driver ethtool with show this information:
Settings for eth1:
	Supported ports: [ TP	 MII ]
	Supported link modes:   Not reported
	Supported pause frame use: Symmetric Receive-only
	Supports auto-negotiation: Yes
	Supported FEC modes: Not reported
	Advertised link modes:  Not reported
	Advertised pause frame use: No
	Advertised auto-negotiation: Yes
	Advertised FEC modes: Not reported
	Speed: 10Mb/s
	Duplex: Full
	Auto-negotiation: on
	master-slave cfg: unknown
	master-slave status: unknown
	Port: Twisted Pair
	PHYAD: 1
	Transceiver: external
	MDI-X: Unknown
	Supports Wake-on: pg
	Wake-on: p
        Current message level: 0x00000007 (7)
                               drv probe link
	Link detected: yes

quoted

voltage depends on the end application: cable length, safety requirements. I do
not see how this can be chosen only on auto negotiation. We would need proper
user space interface to let user/integrator set the limits.

I think we are talking at cross purposes here. As far as i understand
T1L supports the data signals to be 2.4Vpp as well as the usual
1Vpp. This is something which can be negotiated in the same way as
master/slave, duplex etc.

I suspect you are talking about the PoE aspects. That is outside the
scope for phylib. PoE in general is not really supported in the Linux
kernel, and probably needs a subsystem of its own.

No, no. I'm talking about data signals configuration (2.4Vpp/1Vpp), which
depends on application and cable length. 1Vpp should not be used with
cable over 200 meter and 2.4Vpp should not be used on safety critical
applications. 

Regards,
Oleksij
-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |