Re: [net-next PATCH v6 06/10] net: pcs: Add Xilinx PCS driver

On 6/11/25 01:11, Maxime Chevallier wrote:

Hi Sean,

I only 

On Tue, 10 Jun 2025 19:31:30 -0400
Sean Anderson [off-list ref] wrote:

quoted

This adds support for the Xilinx 1G/2.5G Ethernet PCS/PMA or SGMII device.
This is a soft device which converts between GMII and either SGMII,
1000Base-X, or 2500Base-X. If configured correctly, it can also switch
between SGMII and 1000BASE-X at runtime. Thoretically this is also possible
for 2500Base-X, but that requires reconfiguring the serdes. The exact
capabilities depend on synthesis parameters, so they are read from the
devicetree.

This device has a c22-compliant PHY interface, so for the most part we can
just use the phylink helpers. This device supports an interrupt which is
triggered on autonegotiation completion. I'm not sure how useful this is,
since we can never detect a link down (in the PCS).

This device supports sharing some logic between different implementations
of the device. In this case, one device contains the "shared logic" and the
clocks are connected to other devices. To coordinate this, one device
registers a clock that the other devices can request.  The clock is enabled
in the probe function by releasing the device from reset. There are no othe
software controls, so the clock ops are empty.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

Changes in v6:
- Move axienet_pcs_fixup to AXI Ethernet commit
- Use an empty statement for next label

Changes in v5:
- Export get_phy_c22_id when it is used
- Expose bind attributes, since there is no issue in doing so
- Use MDIO_BUS instead of MDIO_DEVICE

Changes in v4:
- Re-add documentation for axienet_xilinx_pcs_get that was accidentally
  removed

Changes in v3:
- Adjust axienet_xilinx_pcs_get for changes to pcs_find_fwnode API
- Call devm_pcs_register instead of devm_pcs_register_provider

Changes in v2:
- Add support for #pcs-cells
- Change compatible to just xlnx,pcs
- Drop PCS_ALTERA_TSE which was accidentally added while rebasing
- Rework xilinx_pcs_validate to just clear out half-duplex modes instead
  of constraining modes based on the interface.

 MAINTAINERS                  |   6 +
 drivers/net/pcs/Kconfig      |  22 ++
 drivers/net/pcs/Makefile     |   2 +
 drivers/net/pcs/pcs-xilinx.c | 427 +++++++++++++++++++++++++++++++++++
 drivers/net/phy/phy_device.c |   3 +-
 include/linux/phy.h          |   1 +
 6 files changed, 460 insertions(+), 1 deletion(-)
 create mode 100644 drivers/net/pcs/pcs-xilinx.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 0ac6ba5c40cb..496513837921 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -27060,6 +27060,12 @@ L:	netdev@vger.kernel.org
 S:	Orphan
 F:	drivers/net/ethernet/xilinx/ll_temac*
 
+XILINX PCS DRIVER
+M:	Sean Anderson <sean.anderson@linux.dev>
+S:	Maintained
+F:	Documentation/devicetree/bindings/net/xilinx,pcs.yaml
+F:	drivers/net/pcs/pcs-xilinx.c
+
 XILINX PWM DRIVER
 M:	Sean Anderson <sean.anderson@seco.com>
 S:	Maintained

diff --git a/drivers/net/pcs/Kconfig b/drivers/net/pcs/Kconfig
index f42839a0c332..e0223914362b 100644
--- a/drivers/net/pcs/Kconfig
+++ b/drivers/net/pcs/Kconfig

@@ -52,4 +52,26 @@ config PCS_RZN1_MIIC
 	  on RZ/N1 SoCs. This PCS converts MII to RMII/RGMII or can be set in
 	  pass-through mode for MII.
 
+config PCS_XILINX
+	tristate "Xilinx PCS driver"
+	default XILINX_AXI_EMAC
+	select COMMON_CLK
+	select GPIOLIB
+	select MDIO_BUS
+	select OF
+	select PCS
+	select PHYLINK
+	help
+	  PCS driver for the Xilinx 1G/2.5G Ethernet PCS/PMA or SGMII device.
+	  This device can either act as a PCS+PMA for 1000BASE-X or 2500BASE-X,
+	  or as a GMII-to-SGMII bridge. It can also switch between 1000BASE-X
+	  and SGMII dynamically if configured correctly when synthesized.
+	  Typical applications use this device on an FPGA connected to a GEM or
+	  TEMAC on the GMII side. The other side is typically connected to
+	  on-device gigabit transceivers, off-device SERDES devices using TBI,
+	  or LVDS IO resources directly.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pcs-xilinx.
+
 endmenu

diff --git a/drivers/net/pcs/Makefile b/drivers/net/pcs/Makefile
index 35e3324fc26e..347afd91f034 100644
--- a/drivers/net/pcs/Makefile
+++ b/drivers/net/pcs/Makefile

@@ -10,3 +10,5 @@ obj-$(CONFIG_PCS_XPCS)		+= pcs_xpcs.o
 obj-$(CONFIG_PCS_LYNX)		+= pcs-lynx.o
 obj-$(CONFIG_PCS_MTK_LYNXI)	+= pcs-mtk-lynxi.o
 obj-$(CONFIG_PCS_RZN1_MIIC)	+= pcs-rzn1-miic.o
+obj-$(CONFIG_PCS_ALTERA_TSE)	+= pcs-altera-tse.o

There's something strange going-on here, as pcs-altera-tse was removed
in v6.4 :)

Ah, well as it happens I have been working on this series since at least
5.10, so I guess it is left over. I will remove it for v7.

--Sean