Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

[abhijit]

Hi All,

We are using Ethernet MAC which has integrated Phy. This phy supports 
speed up to 10000Mbps. The phy has, 1000Base-X PCS(Physical Coding 
Sub-layer) followed by SerDes interface to support 10Mbps to 10000Mbps. 
Currently we are trying to get this phy at 2500Mbps. This device has 16 
registers that corresponds to Clause 37, which can be used to advertise 
speed till 1000Mbps.
So my question is,
1. Without phy advertising its capability of 2500Mbps, is there any way 
I can set phy speed at 2500Mbps?
2. I tried disabling auto-negotiation and setting speed at 2500Mbps with 
ethtool (ethtool -s eth0  speed 2500 autoneg off), but the ethtool 
reported this configuration as invalid?
3. At the end we are targeting print of "link up (2500/Full)"

Regards,
   Abhijit

Re: Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

[Andrew Lunn]

On Tue, Feb 05, 2019 at 11:39:34AM +0530, abhijit wrote:
> Hi All,
> 
> We are using Ethernet MAC which has integrated Phy. This phy supports speed
> up to 10000Mbps. The phy has, 1000Base-X PCS(Physical Coding Sub-layer)
> followed by SerDes interface to support 10Mbps to 10000Mbps. Currently we
> are trying to get this phy at 2500Mbps. This device has 16 registers that
> corresponds to Clause 37, which can be used to advertise speed till
> 1000Mbps.
> So my question is,
> 1. Without phy advertising its capability of 2500Mbps, is there any way I
> can set phy speed at 2500Mbps?
> 2. I tried disabling auto-negotiation and setting speed at 2500Mbps with
> ethtool (ethtool -s eth0  speed 2500 autoneg off), but the ethtool reported
> this configuration as invalid?
> 3. At the end we are targeting print of "link up (2500/Full)"

Hi Abhijit

It all depends on what the PHY driver can do. It sounds like the PHY
driver does not support multi-gige speeds. So you probably need to
work on the PHY driver and add support for them.

What PHY is it?

     Andrew

Re: Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

[abhijit]

Hi Andrew,

Thank you very much for reply.

Please see my reply in-line


On Tuesday 05 February 2019 08:26 PM, Andrew Lunn wrote:
> On Tue, Feb 05, 2019 at 11:39:34AM +0530, abhijit wrote:
>> Hi All,
>>
>> We are using Ethernet MAC which has integrated Phy. This phy supports speed
>> up to 10000Mbps. The phy has, 1000Base-X PCS(Physical Coding Sub-layer)
>> followed by SerDes interface to support 10Mbps to 10000Mbps. Currently we
>> are trying to get this phy at 2500Mbps. This device has 16 registers that
>> corresponds to Clause 37, which can be used to advertise speed till
>> 1000Mbps.
>> So my question is,
>> 1. Without phy advertising its capability of 2500Mbps, is there any way I
>> can set phy speed at 2500Mbps?
>> 2. I tried disabling auto-negotiation and setting speed at 2500Mbps with
>> ethtool (ethtool -s eth0  speed 2500 autoneg off), but the ethtool reported
>> this configuration as invalid?
>> 3. At the end we are targeting print of "link up (2500/Full)"
> Hi Abhijit
>
> It all depends on what the PHY driver can do.
> It sounds like the PHY
> driver does not support multi-gige speeds. So you probably need to
> work on the PHY driver and add support for them.
Currently, we don't have any phy drivers. Generic driver doesn't seems 
to support 2500Mbps. If I have to write the driver, whether it is 
necessary for phy device to advertise speed of 2500Mbps?
>
> What PHY is it?
Phy is custom phy and is currently under test. If you know any phy 
device that supports 2500Mbps and whose data sheet is available freely 
please let me know.
>
>       Andrew

Re: Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

[Andrew Lunn]

> Currently, we don't have any phy drivers. Generic driver doesn't seems to
> support 2500Mbps.

Correct. genphy only supports upto 1G. The c45 based genphy_c45 is
slowly gaining more features and might soon support 2.5G.

> If I have to write the driver, whether it is necessary for
> phy device to advertise speed of 2500Mbps?

The user could force it, using the ethool command you suggested. But
it is the PHY driver which configures this. If you add the driver code
to force it, you might as well add the driver code to allow it to be
negotiated.

> Phy is custom phy and is currently under test. If you know any phy device
> that supports 2500Mbps and whose data sheet is available freely please let
> me know.

There are none that i know of with open data sheets. However the IEEE
standards should be freely available and they describe the registers
the PHY is expected to have. There are also patches floating around
which add 2.5G and 5G support to the marvell10g driver. I expect these
patches to get merged soon, but maybe in a different form to make
genphy_c45 more generic.

	   Andrew

Re: Is advertising of 2500Mbps support must from phy device to set phy at 2500Mbps link speed

[abhijit]

Thanks Andrew for your reply. I will have look at IEEE document and c45.


On Wednesday 06 February 2019 07:08 PM, Andrew Lunn wrote:
>> Currently, we don't have any phy drivers. Generic driver doesn't seems to
>> support 2500Mbps.
> Correct. genphy only supports upto 1G. The c45 based genphy_c45 is
> slowly gaining more features and might soon support 2.5G.
>
>> If I have to write the driver, whether it is necessary for
>> phy device to advertise speed of 2500Mbps?
> The user could force it, using the ethool command you suggested. But
> it is the PHY driver which configures this. If you add the driver code
> to force it, you might as well add the driver code to allow it to be
> negotiated.
>
>> Phy is custom phy and is currently under test. If you know any phy device
>> that supports 2500Mbps and whose data sheet is available freely please let
>> me know.
> There are none that i know of with open data sheets. However the IEEE
> standards should be freely available and they describe the registers
> the PHY is expected to have. There are also patches floating around
> which add 2.5G and 5G support to the marvell10g driver. I expect these
> patches to get merged soon, but maybe in a different form to make
> genphy_c45 more generic.
>
> 	   Andrew