sfc: use budget for TX completions

When running workloads heavy unbalanced towards TX (high TX, low RX
traffic), sfc driver can retain the CPU during too long times. Although
in many cases this is not enough to be visible, it can affect
performance and system responsiveness.

A way to reproduce it is to use a debug kernel and run some parallel
netperf TX tests. In some systems, this will lead to this message being
logged:
kernel:watchdog: BUG: soft lockup - CPU#12 stuck for 22s!

The reason is that sfc driver doesn't account any NAPI budget for the TX
completion events work. With high-TX/low-RX traffic, this makes that the
CPU is held for long time for NAPI poll.

Documentations says "drivers can process completions for any number of Tx
packets but should only process up to budget number of Rx packets".
However, many drivers do limit the amount of TX completions that they
process in a single NAPI poll.

In the same way, this patch adds a limit for the TX work in sfc. With
the patch applied, the watchdog warning never appears.

Tested with netperf in different combinations: single process / parallel
processes, TCP / UDP and different sizes of UDP messages. Repeated the
tests before and after the patch, without any noticeable difference in
network or CPU performance.

Test hardware:
Intel(R) Xeon(R) CPU E5-1620 v4 @ 3.50GHz (4 cores, 2 threads/core)
Solarflare Communications XtremeScale X2522-25G Network Adapter

Fixes: 5227ecccea2d ("sfc: remove tx and MCDI handling from NAPI budget consideration")
Fixes: d19a53721863 ("sfc_ef100: TX path for EF100 NICs")
Reported-by: Fei Liu <feliu@redhat.com>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20230615084929.10506-1-ihuguet@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

sfc: support passing a representor to the EF100 TX path

A non-null efv in __ef100_enqueue_skb() indicates that the packet is
from that representor, should be transmitted with a suitable option
descriptor (to instruct the switch to deliver it to the representee),
and should not be accounted to the parent PF's stats or BQL.

Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

sfc: make ef100 xmit_more handling look more like ef10's

This should cause no functional change; merely make there only be one
design of xmit_more handling to understand. As with the EF10/Siena
version, we set tx_queue->xmit_pending when we queue up a TX, and
clear it when we ring the doorbell (in ef100_notify_tx_desc).
While we're at it, make ef100_notify_tx_desc static since nothing
outside of ef100_tx.c uses it.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

sfc_ef100: TX path for EF100 NICs

Includes checksum offload and TSO, so declare those in our netdev features.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

sfc_ef100: implement ndo_open/close and EVQ probing

Channels are probed, but actual event handling is still stubbed out.

Stub implementation of check_caps is needed because ptp.c will call into
it from efx_ptp_use_mac_tx_timestamps() to decide if it wants TXQs.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

sfc: skeleton EF100 PF driver

No TX or RX path, no MCDI, not even an ifup/down handler.
Besides stubs, the bulk of the patch deals with reading the Xilinx
extended PCIe capability, which tells us where to find our BAR.

Though in the same module, EF100 has its own struct pci_driver,
which is named sfc_ef100.

A small number of additional nic_type methods are added; those in the
TX (tx_enqueue) and RX (rx_packet) paths are called through indirect
call wrappers to minimise the performance impact.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>