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

From: Arınç ÜNAL
Date: Fri Mar 31 2023 - 10:12:49 EST

On 31.03.2023 17:10, Daniel Golle wrote:
On Fri, Mar 31, 2023 at 04:18:19PM +0300, Arınç ÜNAL wrote:
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@xxxxxxxxxxxxxx>
---
   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@xxxxxxxxxxxx>
   M:    Landen Chao <Landen.Chao@xxxxxxxxxxxx>
   M:    DENG Qingfang <dqfext@xxxxxxxxx>
+M:    Daniel Golle <daniel@xxxxxxxxxxxxxx>
   L:    netdev@xxxxxxxxxxxxxxx
   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
^^^^^^
You probably meant MT7988.

The built-in Fast Ethernet switch of older Ralink SoCs as well as MT7628 and
MT7688 is a whole different story:
https://github.com/stroese/linux/blob/gardena-v5.5/drivers/net/dsa/mt7628-esw.c

Yup, typo. "is" at the end should also be "are".

Arınç