linux-kernel - Re: [PATCH net-next 2/2] ARM: dts: aspeed: elbert: Enable mac3 controller

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Message-ID: <45cdae58-632a-7cbb-c9d5-74c126ba6a3e@gmail.com>
Date:   Tue, 6 Sep 2022 10:05:46 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Tao Ren <rentao.bupt@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Heyi Guo <guoheyi@...ux.alibaba.com>,
        Dylan Hung <dylan_hung@...eedtech.com>,
        Guangbin Huang <huangguangbin2@...wei.com>,
        Liang He <windhl@....com>, Hao Chen <chenhao288@...ilicon.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>, Tao Ren <taoren@...com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] ARM: dts: aspeed: elbert: Enable mac3
 controller



On 9/6/2022 4:55 AM, Andrew Lunn wrote:
> On Mon, Sep 05, 2022 at 06:41:33PM -0700, Tao Ren wrote:
>> Hi Andrew,
>>
>> On Tue, Sep 06, 2022 at 02:22:50AM +0200, Andrew Lunn wrote:
>>> On Mon, Sep 05, 2022 at 04:56:34PM -0700, rentao.bupt@...il.com wrote:
>>>> From: Tao Ren <rentao.bupt@...il.com>
>>>>
>>>> Enable mac3 controller in Elbert dts: Elbert MAC3 is connected to the
>>>> onboard switch directly (fixed link).
>>>
>>> What is the switch? Could you also add a DT node for it?
>>>
>>>>
>>>> Signed-off-by: Tao Ren <rentao.bupt@...il.com>
>>>> ---
>>>>   arch/arm/boot/dts/aspeed-bmc-facebook-elbert.dts | 11 +++++++++++
>>>>   1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/arch/arm/boot/dts/aspeed-bmc-facebook-elbert.dts b/arch/arm/boot/dts/aspeed-bmc-facebook-elbert.dts
>>>> index 27b43fe099f1..52cb617783ac 100644
>>>> --- a/arch/arm/boot/dts/aspeed-bmc-facebook-elbert.dts
>>>> +++ b/arch/arm/boot/dts/aspeed-bmc-facebook-elbert.dts
>>>> @@ -183,3 +183,14 @@ imux31: i2c@7 {
>>>>   &i2c11 {
>>>>   	status = "okay";
>>>>   };
>>>> +
>>>> +&mac3 {
>>>> +	status = "okay";
>>>> +	phy-mode = "rgmii";
>>>
>>> 'rgmii' is suspicious, though not necessarily wrong. This value is
>>> normally passed to the PHY, so the PHY inserts the RGMII delay. You
>>> however don't have a PHY. So i assume the switch is inserting the
>>> delay? Again, being able to see the DT properties for the switch would
>>> be useful.
>>>
>>>     Andrew
>>
>> Thank you for the quick review!
>>
>> The BMC mac3 is connected to BCM53134P's IMP_RGMII port, and there is no
>> PHY between BMC MAC and BCM53134P. BCM53134P loads configurations from
>> its EEPROM when the chip is powered.
> 
> So i assume you have the switch RGMII port doing the delays. That is
> fine.
> 
>> Could you please point me an example showing how to describe the switch in
>> dts? Anyhow I will need to improve the patch description and comments in
>> v2.
> 
> It looks like drivers/net/dsa/b53 does not support this particular
> switch. You could consider extending the driver. See
> 
> Documentation/devicetree/bindings/net/dsa/brcm,b53.yaml
> 
> for documentation of the binding.

Correct the 53134 is not supported at the moment by the b53 driver, 
however it should not be too hard to support it, if you would be willing 
to add it, I would be glad to review patches.
-- 
Florian