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

From: Arınç ÜNAL
Date: Fri Mar 31 2023 - 16:09:03 EST

On 31.03.2023 16:18, 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

Looks like PCS_MTK_LYNXI is used on NET_DSA_MT7530_MDIO instead now. I also see '#include <linux/pcs/pcs-mtk-lynxi.h>' on mt7530.c but don't see any functions called on it. Leftover?

    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"

Should go here:

select PCS_MTK_LYNXI

Arınç