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From: Steen Hegelund <steen.hegelund@microchip.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Device Tree List <devicetree@vger.kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	"Lars Povlsen" <lars.povlsen@microchip.com>,
	Bjarni Jonasson <bjarni.jonasson@microchip.com>,
	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Madalin Bucur <madalin.bucur@oss.nxp.com>,
	Nicolas Ferre <nicolas.ferre@microchip.com>,
	Mark Einon <mark.einon@gmail.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, <netdev@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH v2 8/8] arm64: dts: sparx5: Add the Sparx5 switch node
Date: Wed, 23 Dec 2020 15:31:24 +0100	[thread overview]
Message-ID: <20201223143124.tr2vejqgpf2qsot2@mchp-dev-shegelun> (raw)
In-Reply-To: <20201219202448.GE3026679@lunn.ch>

On 19.12.2020 21:24, Andrew Lunn wrote:
>EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
>> +             port13: port@13 {
>> +                     reg = <13>;
>> +                     /* Example: CU SFP, 1G speed */
>> +                     max-speed = <10000>;
>
>One too many 0's for 1G.

Ah, but this is allocation for the port, not the speed.  This just
used by the calendar module to allocate slots on the taxis as requested.
So I would say it is OK to overallocate in this case (but you could
argue it does not make much sense).

>
>> +             /* 25G SFPs */
>> +             port56: port@56 {
>> +                     reg = <56>;
>> +                     max-speed = <10000>;
>
>Why limit a 25G SFP to 10G?

In the PCB134 case it is to keep the total allocation below 200Gbits
((12+8)*10G).  There is a port mux mode that provides 8*25G on the 25G
SerDes'es, but that would be a different DT.

The Datasheet shows which port mux combinations are possible, and not
all combinations of SerDes, Speed and interface are allowed.

The PCB134 was designed to showcase this "many 10G ports" mode, so that
is why we have the current DT.

>
>    Andrew

BR
Steen

---------------------------------------
Steen Hegelund
steen.hegelund@microchip.com

WARNING: multiple messages have this Message-ID (diff)
From: Steen Hegelund <steen.hegelund@microchip.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Device Tree List <devicetree@vger.kernel.org>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Bjarni Jonasson <bjarni.jonasson@microchip.com>,
	Madalin Bucur <madalin.bucur@oss.nxp.com>,
	netdev@vger.kernel.org, Masahiro Yamada <masahiroy@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
	Rob Herring <robh+dt@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Mark Einon <mark.einon@gmail.com>,
	Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Lars Povlsen <lars.povlsen@microchip.com>
Subject: Re: [RFC PATCH v2 8/8] arm64: dts: sparx5: Add the Sparx5 switch node
Date: Wed, 23 Dec 2020 15:31:24 +0100	[thread overview]
Message-ID: <20201223143124.tr2vejqgpf2qsot2@mchp-dev-shegelun> (raw)
In-Reply-To: <20201219202448.GE3026679@lunn.ch>

On 19.12.2020 21:24, Andrew Lunn wrote:
>EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
>> +             port13: port@13 {
>> +                     reg = <13>;
>> +                     /* Example: CU SFP, 1G speed */
>> +                     max-speed = <10000>;
>
>One too many 0's for 1G.

Ah, but this is allocation for the port, not the speed.  This just
used by the calendar module to allocate slots on the taxis as requested.
So I would say it is OK to overallocate in this case (but you could
argue it does not make much sense).

>
>> +             /* 25G SFPs */
>> +             port56: port@56 {
>> +                     reg = <56>;
>> +                     max-speed = <10000>;
>
>Why limit a 25G SFP to 10G?

In the PCB134 case it is to keep the total allocation below 200Gbits
((12+8)*10G).  There is a port mux mode that provides 8*25G on the 25G
SerDes'es, but that would be a different DT.

The Datasheet shows which port mux combinations are possible, and not
all combinations of SerDes, Speed and interface are allowed.

The PCB134 was designed to showcase this "many 10G ports" mode, so that
is why we have the current DT.

>
>    Andrew

BR
Steen

---------------------------------------
Steen Hegelund
steen.hegelund@microchip.com

_______________________________________________
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  reply	other threads:[~2020-12-23 14:32 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-17  7:51 [RFC PATCH v2 0/8] Adding the Sparx5 Switch Driver Steen Hegelund
2020-12-17  7:51 ` Steen Hegelund
2020-12-17  7:51 ` [RFC PATCH v2 1/8] dt-bindings: net: sparx5: Add sparx5-switch bindings Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-19 17:54   ` Andrew Lunn
2020-12-19 17:54     ` Andrew Lunn
2020-12-21  0:55   ` Florian Fainelli
2020-12-21  0:55     ` Florian Fainelli
2020-12-21 10:00     ` Steen Hegelund
2020-12-21 10:00       ` Steen Hegelund
2020-12-21 21:40   ` Rob Herring
2020-12-21 21:40     ` Rob Herring
2020-12-22  7:30     ` Steen Hegelund
2020-12-22  7:30       ` Steen Hegelund
2020-12-17  7:51 ` [RFC PATCH v2 2/8] net: sparx5: add the basic sparx5 driver Steen Hegelund
2020-12-19 19:11   ` Andrew Lunn
2020-12-19 19:11     ` Andrew Lunn
2020-12-22 13:50     ` Steen Hegelund
2020-12-22 13:50       ` Steen Hegelund
2020-12-22 15:01       ` Andrew Lunn
2020-12-22 15:01         ` Andrew Lunn
2020-12-22 16:56         ` Alexandre Belloni
2020-12-22 16:56           ` Alexandre Belloni
2020-12-23  9:03           ` Lars Povlsen
2020-12-23  9:03             ` Lars Povlsen
2020-12-23  8:52         ` Steen Hegelund
2020-12-23  8:52           ` Steen Hegelund
2020-12-17  7:51 ` [RFC PATCH v2 3/8] net: sparx5: add hostmode with phylink support Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-19 19:51   ` Andrew Lunn
2020-12-19 19:51     ` Andrew Lunn
2020-12-22  9:46     ` Steen Hegelund
2020-12-22  9:46       ` Steen Hegelund
2020-12-22 14:41       ` Andrew Lunn
2020-12-22 14:41         ` Andrew Lunn
2020-12-23 13:29         ` Steen Hegelund
2020-12-23 13:29           ` Steen Hegelund
2020-12-23 20:58         ` Alexandre Belloni
2020-12-23 20:58           ` Alexandre Belloni
2020-12-23 21:05           ` Andrew Lunn
2020-12-23 21:05             ` Andrew Lunn
2020-12-17  7:51 ` [RFC PATCH v2 4/8] net: sparx5: add port module support Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-20 23:35   ` Andrew Lunn
2020-12-20 23:35     ` Andrew Lunn
2020-12-22 14:55     ` Bjarni Jonasson
2020-12-22 14:55       ` Bjarni Jonasson
2020-12-22 15:08       ` Andrew Lunn
2020-12-22 15:08         ` Andrew Lunn
2020-12-17  7:51 ` [RFC PATCH v2 5/8] net: sparx5: add switching, vlan and mactable support Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-21  0:25   ` Andrew Lunn
2020-12-21  0:25     ` Andrew Lunn
2020-12-23 13:54     ` Steen Hegelund
2020-12-23 13:54       ` Steen Hegelund
2020-12-17  7:51 ` [RFC PATCH v2 6/8] net: sparx5: add calendar bandwidth allocation support Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-17  7:51 ` [RFC PATCH v2 7/8] net: sparx5: add ethtool configuration and statistics support Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-19 23:31   ` Andrew Lunn
2020-12-19 23:31     ` Andrew Lunn
2020-12-17  7:51 ` [RFC PATCH v2 8/8] arm64: dts: sparx5: Add the Sparx5 switch node Steen Hegelund
2020-12-17  7:51   ` Steen Hegelund
2020-12-19 20:24   ` Andrew Lunn
2020-12-19 20:24     ` Andrew Lunn
2020-12-23 14:31     ` Steen Hegelund [this message]
2020-12-23 14:31       ` Steen Hegelund
2020-12-23 15:49       ` Andrew Lunn
2020-12-23 15:49         ` Andrew Lunn
2020-12-21  0:58 ` [RFC PATCH v2 0/8] Adding the Sparx5 Switch Driver Florian Fainelli
2020-12-21  0:58   ` Florian Fainelli
2020-12-21 14:31   ` Steen Hegelund
2020-12-21 14:31     ` Steen Hegelund
2020-12-22 11:29   ` Lars Povlsen
2020-12-22 11:29     ` Lars Povlsen

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