mlxbf_gige: Fix intermittent no ip issue

Although the link is up, there is no ip assigned on setups with high background
traffic. Nothing is transmitted nor received. The RX error count keeps on
increasing. After several minutes, the RX error count stagnates and the
GigE interface finally gets an ip.

The issue is that mlxbf_gige_rx_init() is called before phy_start().
As soon as the RX DMA is enabled in mlxbf_gige_rx_init(), the RX CI reaches the max
of 128, and becomes equal to RX PI. RX CI doesn't decrease since the code hasn't
ran phy_start yet.
Bring the PHY up before starting the RX.

Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
Reviewed-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

mlxbf_gige: fix receive packet race condition

Under heavy traffic, the BlueField Gigabit interface can
become unresponsive. This is due to a possible race condition
in the mlxbf_gige_rx_packet function, where the function exits
with producer and consumer indices equal but there are remaining
packet(s) to be processed. In order to prevent this situation,
read receive consumer index *before* the HW replenish so that
the mlxbf_gige_rx_packet function returns an accurate return
value even if a packet is received into just-replenished buffer
prior to exiting this routine. If the just-replenished buffer
is received and occupies the last RX ring entry, the interface
would not recover and instead would encounter RX packet drops
related to internal buffer shortages since the driver RX logic
is not being triggered to drain the RX ring. This patch will
address and prevent this "ring full" condition.

Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
Reviewed-by: Asmaa Mnebhi <asmaa@nvidia.com>
Signed-off-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: mellanox: mlxbf_gige: Fix skb_panic splat under memory pressure

Do skb_put() after a new skb has been successfully allocated otherwise
the reused skb leads to skb_panics or incorrect packet sizes.

Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230524194908.147145-1-tbogendoerfer@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add Mellanox BlueField Gigabit Ethernet driver

This patch adds build and driver logic for the "mlxbf_gige"
Ethernet driver from Mellanox Technologies. The second
generation BlueField SoC from Mellanox supports an
out-of-band GigaBit Ethernet management port to the Arm
subsystem. This driver supports TCP/IP network connectivity
for that port, and provides back-end routines to handle
basic ethtool requests.

The driver interfaces to the Gigabit Ethernet block of
BlueField SoC via MMIO accesses to registers, which contain
control information or pointers describing transmit and
receive resources. There is a single transmit queue, and
the port supports transmit ring sizes of 4 to 256 entries.
There is a single receive queue, and the port supports
receive ring sizes of 32 to 32K entries. The transmit and
receive rings are allocated from DMA coherent memory. There
is a 16-bit producer and consumer index per ring to denote
software ownership and hardware ownership, respectively.

The main driver logic such as probe(), remove(), and netdev
ops are in "mlxbf_gige_main.c". Logic in "mlxbf_gige_rx.c"
and "mlxbf_gige_tx.c" handles the packet processing for
receive and transmit respectively.

The logic in "mlxbf_gige_ethtool.c" supports the handling
of some basic ethtool requests: get driver info, get ring
parameters, get registers, and get statistics.

The logic in "mlxbf_gige_mdio.c" is the driver controlling
the Mellanox BlueField hardware that interacts with a PHY
device via MDIO/MDC pins. This driver does the following:
- At driver probe time, it configures several BlueField MDIO
parameters such as sample rate, full drive, voltage and MDC
- It defines functions to read and write MDIO registers and
registers the MDIO bus.
- It defines the phy interrupt handler reporting a
link up/down status change
- This driver's probe is invoked from the main driver logic
while the phy interrupt handler is registered in ndo_open.

Driver limitations
- Only supports 1Gbps speed
- Only supports GMII protocol
- Supports maximum packet size of 2KB
- Does not support scatter-gather buffering

Testing
- Successful build of kernel for ARM64, ARM32, X86_64
- Tested ARM64 build on FastModels & Palladium
- Tested ARM64 build on several Mellanox boards that are built with
the BlueField-2 SoC. The testing includes coverage in the areas
of networking (e.g. ping, iperf, ifconfig, route), file transfers
(e.g. SCP), and various ethtool options relevant to this driver.

Signed-off-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
Reviewed-by: Liming Sun <limings@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>