drivers: ethernet: add support for Xilinx GEM controller

Add support for the Xilinx GEM Ethernet controller, which is integrated
in both the Xilinx Zynq and ZynqMP (UltraScale) SoC families. The driver
supports the management of a PHY attached to the respective GEM's MDIO
interface.

This driver was developed with ultimately the Zynq-7000 series in mind,
but at the time being, it is limited to use in conjunction with the
ZynqMP RPU (Cortex-R5) cores. The differences are minor when it comes
to the adjustment of the TX clock frequency derived from the current
link speed reported by the PHY, but for use in conjunction with the
Zynq-7000, some larger adjustments will have to be made when it comes
to the placement of the DMA memory area, as this involves the confi-
guration of the MMU in Cortex-A CPUs.

The driver was developed under the qemu_cortex_r5 target. The Marvell
88E1111 PHY simulated by QEMU is supported by the driver.

Limitations currently exist when it comes to timestamping or VLAN
support and other minor things. Those haven't been implemented yet,
although they are supported by the hardware. In order to be fully
supported by the ZynqMP APU, 64-bit DMA address descriptor format
support will be added.

Signed-off-by: Immo Birnbaum <Immo.Birnbaum@weidmueller.com>
9 files changed