netdev - Re: [PATCH next-next] net: phy: realtek: add support for rtl8224 2.5Gbps PHY

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Date: Wed, 12 Jun 2024 20:39:37 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: Marek Behún <kabel@...nel.org>
CC: "andrew@...n.ch" <andrew@...n.ch>, "hkallweit1@...il.com"
	<hkallweit1@...il.com>, "linux@...linux.org.uk" <linux@...linux.org.uk>,
	"davem@...emloft.net" <davem@...emloft.net>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "ericwouds@...il.com" <ericwouds@...il.com>
Subject: Re: [PATCH next-next] net: phy: realtek: add support for rtl8224
 2.5Gbps PHY


On 12/06/24 19:07, Marek Behún wrote:
> On Tue, 11 Jun 2024 20:42:43 +0000
> Chris Packham <Chris.Packham@...iedtelesis.co.nz> wrote:
>
>> +cc Eric W and Marek.
>>
>> On 11/06/24 17:34, Chris Packham wrote:
>>> The Realtek RTL8224 PHY is a 2.5Gbps capable PHY. It only uses the
>>> clause 45 MDIO interface and can leverage the support that has already
>>> been added for the other 822x PHYs.
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>
>>> Notes:
>>>       I'm currently testing this on an older kernel because the board I'm
>>>       using has a SOC/DSA switch that has a driver in openwrt for Linux 5.15.
>>>       I have tried to selectively back port the bits I need from the other
>>>       rtl822x work so this should be all that is required for the rtl8224.
>>>       
>>>       There's quite a lot that would need forward porting get a working system
>>>       against a current kernel so hopefully this is small enough that it can
>>>       land while I'm trying to figure out how to untangle all the other bits.
>>>       
>>>       One thing that may appear lacking is the lack of rate_matching support.
>>>       According to the documentation I have know the interface used on the
>>>       RTL8224 is (q)uxsgmii so no rate matching is required. As I'm still
>>>       trying to get things completely working that may change if I get new
>>>       information.
>>>
>>>    drivers/net/phy/realtek.c | 8 ++++++++
>>>    1 file changed, 8 insertions(+)
>>>
>>> diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
>>> index 7ab41f95dae5..2174893c974f 100644
>>> --- a/drivers/net/phy/realtek.c
>>> +++ b/drivers/net/phy/realtek.c
>>> @@ -1317,6 +1317,14 @@ static struct phy_driver realtek_drvs[] = {
>>>    		.resume         = rtlgen_resume,
>>>    		.read_page      = rtl821x_read_page,
>>>    		.write_page     = rtl821x_write_page,
>>> +	}, {
>>> +		PHY_ID_MATCH_EXACT(0x001ccad0),
>>> +		.name		= "RTL8224 2.5Gbps PHY",
>>> +		.get_features   = rtl822x_c45_get_features,
>>> +		.config_aneg    = rtl822x_c45_config_aneg,
>>> +		.read_status    = rtl822x_c45_read_status,
>>> +		.suspend        = genphy_c45_pma_suspend,
>>> +		.resume         = rtlgen_c45_resume,
>>>    	}, {
>>>    		PHY_ID_MATCH_EXACT(0x001cc961),
>>>    		.name		= "RTL8366RB Gigabit Ethernet"
> Don't you need rtl822xb_config_init for serdes configuration?

I more than likely need a config_init() function. I'm working with 
incomplete datasheets so I'm not sure if rtl822xb_config_init() will 
work for me (if anyone has a contact at Realtek I'd like to hear from 
you). The MAC-PHY interface on the RTL8224 is qusxgmii and 
rtl822xb_config_init() seems to only cater for 2500base-x or hsgmii so I 
think I will need a different config_init() but quite what that looks 
like I'm not sure.

That's also where I start running into the backporting problem because 
the rtl822xb_config_init() decides the mode based on the host_interfaces 
which doesn't exist in the kernel I have dsa drivers for. I do plan on 
trying to bring the code I have forward but there's quite a lot I need 
to sift through.