netdev - Re: [PATCH net-next 14/15] net: dsa: mt7530: introduce driver for MT7988 built-in switch

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Date:   Fri, 31 Mar 2023 16:18:19 +0300
From:   Arınç ÜNAL <arinc.unal@...nc9.com>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     netdev@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux@...linux.org.uk,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sam Shih <Sam.Shih@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        John Crispin <john@...ozen.org>, Felix Fietkau <nbd@....name>,
        Luiz Angelo Daros de Luca <luizluca@...il.com>
Subject: Re: [PATCH net-next 14/15] net: dsa: mt7530: introduce driver for
 MT7988 built-in switch

On 31.03.2023 15:06, Arınç ÜNAL wrote:
> On 31.03.2023 13:16, Daniel Golle wrote:
>> On Fri, Mar 31, 2023 at 08:50:28AM +0300, Arınç ÜNAL wrote:
>>> On 30.03.2023 18:23, Daniel Golle wrote:
>>>> Add driver for the built-in Gigabit Ethernet switch which can be found
>>>> in the MediaTek MT7988 SoC.
>>>>
>>>> The switch shares most of its design with MT7530 and MT7531, but has
>>>> it's registers mapped into the SoCs register space rather than being
>>>> connected externally or internally via MDIO.
>>>>
>>>> Introduce a new platform driver to support that.
>>>>
>>>> Signed-off-by: Daniel Golle <daniel@...rotopia.org>
>>>> ---
>>>>    MAINTAINERS                   |   2 +
>>>>    drivers/net/dsa/Kconfig       |  12 ++++
>>>>    drivers/net/dsa/Makefile      |   1 +
>>>>    drivers/net/dsa/mt7530-mmio.c | 101 
>>>> ++++++++++++++++++++++++++++++++++
>>>>    drivers/net/dsa/mt7530.c      |  86 ++++++++++++++++++++++++++++-
>>>>    drivers/net/dsa/mt7530.h      |  12 ++--
>>>>    6 files changed, 206 insertions(+), 8 deletions(-)
>>>>    create mode 100644 drivers/net/dsa/mt7530-mmio.c
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index 14924aed15ca7..674673dbdfd8b 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -13174,9 +13174,11 @@ MEDIATEK SWITCH DRIVER
>>>>    M:    Sean Wang <sean.wang@...iatek.com>
>>>>    M:    Landen Chao <Landen.Chao@...iatek.com>
>>>>    M:    DENG Qingfang <dqfext@...il.com>
>>>> +M:    Daniel Golle <daniel@...rotopia.org>
>>>>    L:    netdev@...r.kernel.org
>>>>    S:    Maintained
>>>>    F:    drivers/net/dsa/mt7530-mdio.c
>>>> +F:    drivers/net/dsa/mt7530-mmio.c
>>>>    F:    drivers/net/dsa/mt7530.*
>>>>    F:    net/dsa/tag_mtk.c
>>>> diff --git a/drivers/net/dsa/Kconfig b/drivers/net/dsa/Kconfig
>>>> index c2551b13324c2..de4d86e37973f 100644
>>>> --- a/drivers/net/dsa/Kconfig
>>>> +++ b/drivers/net/dsa/Kconfig
>>>> @@ -52,6 +52,18 @@ config NET_DSA_MT7530
>>>>          Multi-chip module MT7530 in MT7621AT, MT7621DAT, MT7621ST and
>>>>          MT7623AI SoCs is supported as well.
>>>> +config NET_DSA_MT7988
>>>> +    tristate "MediaTek MT7988 built-in Ethernet switch support"
>>>> +    select NET_DSA_MT7530_COMMON
>>>> +    depends on HAS_IOMEM
>>>> +    help
>>>> +      This enables support for the built-in Ethernet switch found
>>>> +      in the MediaTek MT7988 SoC.
>>>> +      The switch is a similar design as MT7531, however, unlike
>>>> +      other MT7530 and MT7531 the switch registers are directly
>>>> +      mapped into the SoCs register space rather than being accessible
>>>> +      via MDIO.
>>>> +
>>>>    config NET_DSA_MV88E6060
>>>>        tristate "Marvell 88E6060 ethernet switch chip support"
>>>>        select NET_DSA_TAG_TRAILER
>>>> diff --git a/drivers/net/dsa/Makefile b/drivers/net/dsa/Makefile
>>>> index 71250d7dd41af..103a33e20de4b 100644
>>>> --- a/drivers/net/dsa/Makefile
>>>> +++ b/drivers/net/dsa/Makefile
>>>> @@ -8,6 +8,7 @@ endif
>>>>    obj-$(CONFIG_NET_DSA_LANTIQ_GSWIP) += lantiq_gswip.o
>>>>    obj-$(CONFIG_NET_DSA_MT7530_COMMON) += mt7530.o
>>>>    obj-$(CONFIG_NET_DSA_MT7530)    += mt7530-mdio.o
>>>> +obj-$(CONFIG_NET_DSA_MT7988)    += mt7530-mmio.o
>>>
>>> I'm not fond of this way. Wouldn't it be better if we split the mdio and
>>> mmio drivers to separate modules and kept switch hardware support on
>>> mt7530.c?
>>
>> You mean this in terms of Kconfig symbols?
>> Because the way you describe is basically what I'm doing here:
>>   * mt7530.c is the shared/common switch hardware driver
>>   * mt7530-mdio.c contains the MDIO accessors and MDIO device drivers for
>>     MT7530, MT7531, MT7621, MT7623, ...
>>   * mt7530-mmio.c contains the platform device driver for in-SoC switches
>>     which are accessed via MMIO, ie. MT7988 (and yes, this could be
>>     extended to also support MT7620A/N).
> 
> Ok great.
> 
>>
>> In early drafts I also named the Kconfig symbols
>> CONFIG_NET_DSA_MT7530 for mt7530.c (ie. the common part)
>> CONFIG_NET_DSA_MT7530_MDIO for the MDIO driver
>> CONFIG_NET_DSA_MT7530_MMIO for the MMIO driver
>>
>> However, as existing kernel configurations expect 
>> CONFIG_NET_DSA_MT7530 to
>> select the MDIO driver, I decided it would be better to hide the 
>> symbol of
>> the common part and have CONFIG_NET_DSA_MT7530 select the MDIO driver 
>> like
>> it was before.
> 
> You can "imply NET_DSA_MT7530_MDIO" from NET_DSA_MT7530 so the MDIO 
> driver is also enabled when NET_DSA_MT7530 is selected. For example, on 
> Realtek, both MDIO and SMI drivers are enabled by default when either of 
> the main drivers are selected.
> 
> config NET_DSA_MT7530
>      tristate "MediaTek MT7530 and MT7531 Ethernet switch support"
>      select NET_DSA_TAG_MTK
>      select MEDIATEK_GE_PHY
>      select PCS_MTK_LYNXI
>      imply NET_DSA_MT7530_MDIO
>      imply NET_DSA_MT7530_MMIO

The final kconfig should look like this:

config NET_DSA_MT7530
	tristate "MediaTek MT7530 and MT7531 Ethernet switch support"
	select NET_DSA_TAG_MTK
	select MEDIATEK_GE_PHY
	select PCS_MTK_LYNXI
	imply NET_DSA_MT7530_MDIO
	imply NET_DSA_MT7530_MMIO
	help
	  This enables support for the MediaTek MT7530 and MT7531 Ethernet
	  switch chips. Multi-chip module MT7530 in MT7621AT, MT7621DAT,
	  MT7621ST and MT7623AI SoCs, and built-in switch in MT7688 SoC is
	  supported.

config NET_DSA_MT7530_MDIO
	tristate "MediaTek MT7530 MDIO interface driver"
	default NET_DSA_MT7530
	depends on NET_DSA_MT7530
	help
	  This enables support for the MediaTek MT7530 switch chips which are
	  connected via MDIO.

config NET_DSA_MT7530_MMIO
	tristate "MediaTek MT7530 MMIO interface driver"
	depends on HAS_IOMEM
	depends on NET_DSA_MT7530
	help
	  This enables support for the MediaTek MT7530 switch chips which are
	  connected via MMIO.

You should also change MODULE_DESCRIPTION for both drivers to something
like "Driver for MediaTek MT7530 ethernet switches connected via MMIO
interface".

Arınç