net: ethtool: pass a pointer to parameters to get/set_rxfh ethtool ops

The get/set_rxfh ethtool ops currently takes the rxfh (RSS) parameters
as direct function arguments. This will force us to chan

net: ethtool: pass a pointer to parameters to get/set_rxfh ethtool ops

The get/set_rxfh ethtool ops currently takes the rxfh (RSS) parameters
as direct function arguments. This will force us to change the API (and
all drivers' functions) every time some new parameters are added.

This is part 1/2 of the fix, as suggested in [1]:

- First simplify the code by always providing a pointer to all params
(indir, key and func); the fact that some of them may be NULL seems
like a weird historic thing or a premature optimization.
It will simplify the drivers if all pointers are always present.

- Then make the functions take a dev pointer, and a pointer to a
single struct wrapping all arguments. The set_* should also take
an extack.

Link: https://lore.kernel.org/netdev/20231121152906.2dd5f487@kernel.org/ [1]
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Suggested-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Link: https://lore.kernel.org/r/20231213003321.605376-2-ahmed.zaki@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: include MAC Merge / FP registers in register dump

These have been useful in debugging various problems related to frame
preemption, so make them available through ethtool --register-dump

net: enetc: include MAC Merge / FP registers in register dump

These have been useful in debugging various problems related to frame
preemption, so make them available through ethtool --register-dump for
later too.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: enetc: only commit preemptible TCs to hardware when MM TX is active

This was left as TODO in commit 01e23b2b3bad ("net: enetc: add support
for preemptible traffic classes") since it's relativel

net: enetc: only commit preemptible TCs to hardware when MM TX is active

This was left as TODO in commit 01e23b2b3bad ("net: enetc: add support
for preemptible traffic classes") since it's relatively complicated.

Where this makes a difference is with a configuration as follows:

ethtool --set-mm eno0 pmac-enabled on tx-enabled on verify-enabled on

Preemptible packets should only be sent when the MAC Merge TX direction
becomes active (i.o.w. when the verification process succeeds, aka when
the link partner confirms it can process preemptible traffic). But the
tc qdisc with the preemptible traffic classes is offloaded completely
asynchronously w.r.t. the MM becoming active.

The ENETC manual does suggest that this should be handled in the driver:
"On startup, software should wait for the verification process to
complete (MMCSR[VSTS]=011) before initiating traffic".

Adding the necessary logic allows future selftests to uphold the claim
that an inactive or disabled MAC Merge layer should never send data
packets through the pMAC.

This change moves enetc_set_ptcfpr() from enetc.c to enetc_ethtool.c,
where its only caller is now - enetc_mm_commit_preemptible_tcs().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: enetc: report mm tx-active based on tx-enabled and verify-status

The MMCSR register contains 2 fields with overlapping meaning:

- LPA (Local preemption active):
This read-only status bit indic

net: enetc: report mm tx-active based on tx-enabled and verify-status

The MMCSR register contains 2 fields with overlapping meaning:

- LPA (Local preemption active):
This read-only status bit indicates whether preemption is active for
this port. This bit will be set if preemption is both enabled and has
completed the verification process.
- TXSTS (Merge status):
This read-only status field provides the state of the MAC Merge sublayer
transmit status as defined in IEEE Std 802.3-2018 Clause 99.
00 Transmit preemption is inactive
01 Transmit preemption is active
10 Reserved
11 Reserved

However none of these 2 fields offer reliable reporting to software.

When connecting ENETC to a link partner which is not capable of Frame
Preemption, the expectation is that ENETC's verification should fail
(VSTS=4) and its MM TX direction should be inactive (LPA=0, TXSTS=00)
even though the MM TX is enabled (ME=1). But surprise, the LPA bit of
MMCSR stays set even if VSTS=4 and ME=1.

OTOH, the TXSTS field has the opposite problem. I cannot get its value
to change from 0, even when connecting to a link partner capable of
frame preemption, which does respond to its verification frames (ME=1
and VSTS=3, "SUCCEEDED").

The only option with such buggy hardware seems to be to reimplement the
formula for calculating tx-active in software, which is for tx-enabled
to be true, and for the verify-status to be either SUCCEEDED, or
DISABLED.

Without reliable tx-active reporting, we have no good indication when
to commit the preemptible traffic classes to hardware, which makes it
possible (but not desirable) to send preemptible traffic to a link
partner incapable of receiving it. However, currently we do not have the
logic to wait for TX to be active yet, so the impact is limited.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: fix MAC Merge layer remaining enabled until a link down event

Current enetc_set_mm() is designed to set the priv->active_offloads bit
ENETC_F_QBU for enetc_mm_link_state_update() to act

net: enetc: fix MAC Merge layer remaining enabled until a link down event

Current enetc_set_mm() is designed to set the priv->active_offloads bit
ENETC_F_QBU for enetc_mm_link_state_update() to act on, but if the link
is already up, it modifies the ENETC_MMCSR_ME ("Merge Enable") bit
directly.

The problem is that it only *sets* ENETC_MMCSR_ME if the link is up, it
doesn't *clear* it if needed. So subsequent enetc_get_mm() calls still
see tx-enabled as true, up until a link down event, which is when
enetc_mm_link_state_update() will get called.

This is not a functional issue as far as I can assess. It has only come
up because I'd like to uphold a simple API rule in core ethtool code:
the pMAC cannot be disabled if TX is going to be enabled. Currently,
the fact that TX remains enabled for longer than expected (after the
enetc_set_mm() call that disables it) is going to violate that rule,
which is how it was caught.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: enetc: workaround for unresponsive pMAC after receiving express traffic

I have observed an issue where the RX direction of the LS1028A ENETC pMAC
seems unresponsive. The minimal procedure to re

net: enetc: workaround for unresponsive pMAC after receiving express traffic

I have observed an issue where the RX direction of the LS1028A ENETC pMAC
seems unresponsive. The minimal procedure to reproduce the issue is:

1. Connect ENETC port 0 with a loopback RJ45 cable to one of the Felix
switch ports (0).

2. Bring the ports up (MAC Merge layer is not enabled on either end).

3. Send a large quantity of unidirectional (express) traffic from Felix
to ENETC. I tried altering frame size and frame count, and it doesn't
appear to be specific to either of them, but rather, to the quantity
of octets received. Lowering the frame count, the minimum quantity of
packets to reproduce relatively consistently seems to be around 37000
frames at 1514 octets (w/o FCS) each.

4. Using ethtool --set-mm, enable the pMAC in the Felix and in the ENETC
ports, in both RX and TX directions, and with verification on both
ends.

5. Wait for verification to complete on both sides.

6. Configure a traffic class as preemptible on both ends.

7. Send some packets again.

The issue is at step 5, where the verification process of ENETC ends
(meaning that Felix responds with an SMD-R and ENETC sees the response),
but the verification process of Felix never ends (it remains VERIFYING).

If step 3 is skipped or if ENETC receives less traffic than
approximately that threshold, the test runs all the way through
(verification succeeds on both ends, preemptible traffic passes fine).

If, between step 4 and 5, the step below is also introduced:

4.1. Disable and re-enable PM0_COMMAND_CONFIG bit RX_EN

then again, the sequence of steps runs all the way through, and
verification succeeds, even if there was the previous RX traffic
injected into ENETC.

Traffic sent *by* the ENETC port prior to enabling the MAC Merge layer
does not seem to influence the verification result, only received
traffic does.

The LS1028A manual does not mention any relationship between
PM0_COMMAND_CONFIG and MMCSR, and the hardware people don't seem to
know for now either.

The bit that is toggled to work around the issue is also toggled
by enetc_mac_enable(), called from phylink's mac_link_down() and
mac_link_up() methods - which is how the workaround was found:
verification would work after a link down/up.

Fixes: c7b9e8086902 ("net: enetc: add support for MAC Merge layer")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20230411192645.1896048-1-vladimir.oltean@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

show more ...

net: enetc: fix aggregate RMON counters not showing the ranges

When running "ethtool -S eno0 --groups rmon" without an explicit "--src
emac|pmac" argument, the kernel will not report
rx-rmon-etherSt

net: enetc: fix aggregate RMON counters not showing the ranges

When running "ethtool -S eno0 --groups rmon" without an explicit "--src
emac|pmac" argument, the kernel will not report
rx-rmon-etherStatsPkts64to64Octets, rx-rmon-etherStatsPkts65to127Octets,
etc. This is because on ETHTOOL_MAC_STATS_SRC_AGGREGATE, we do not
populate the "ranges" argument.

ocelot_port_get_rmon_stats() does things differently and things work
there. I had forgotten to make sure that the code is structured the same
way in both drivers, so do that now.

Fixes: cf52bd238b75 ("net: enetc: add support for MAC Merge statistics counters")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230321232831.1200905-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: add support for MAC Merge statistics counters

Add PF driver support for the following:

- Viewing the standardized MAC Merge layer counters.

- Viewing the standardized Ethernet MAC and

net: enetc: add support for MAC Merge statistics counters

Add PF driver support for the following:

- Viewing the standardized MAC Merge layer counters.

- Viewing the standardized Ethernet MAC and RMON counters associated
with the pMAC.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230206094531.444988-2-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: add support for MAC Merge layer

Add PF driver support for viewing and changing the MAC Merge sublayer
parameters, and seeing the verification state machine's current state.
The verificat

net: enetc: add support for MAC Merge layer

Add PF driver support for viewing and changing the MAC Merge sublayer
parameters, and seeing the verification state machine's current state.
The verification handshake with the link partner is driven by hardware.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230206094531.444988-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: build common object files into a separate module

The build system is complaining about the following:

enetc.o is added to multiple modules: fsl-enetc fsl-enetc-vf
enetc_cbdr.o is added

net: enetc: build common object files into a separate module

The build system is complaining about the following:

enetc.o is added to multiple modules: fsl-enetc fsl-enetc-vf
enetc_cbdr.o is added to multiple modules: fsl-enetc fsl-enetc-vf
enetc_ethtool.o is added to multiple modules: fsl-enetc fsl-enetc-vf

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net: ethernet: enetc: get rid of xdp_redirect_sg counter

Remove xdp_redirect_sg counter and the related ethtool entry since it is
no longer used.

Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com

net: ethernet: enetc: get rid of xdp_redirect_sg counter

Remove xdp_redirect_sg counter and the related ethtool entry since it is
no longer used.

Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: expose some standardized ethtool counters

Structure the code in such a way that it can be reused later for the
pMAC statistics, by just changing the "mac" argument to 1.

Usage:
ethtool

net: enetc: expose some standardized ethtool counters

Structure the code in such a way that it can be reused later for the
pMAC statistics, by just changing the "mac" argument to 1.

Usage:
ethtool --include-statistics --show-pause eno2
ethtool -S eno0 --groups eth-mac
ethtool -S eno0 --groups eth-ctrl
ethtool -S eno0 --groups rmon

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: parameterize port MAC stats to also cover the pMAC

The ENETC has counters for the eMAC and for the pMAC exactly 0x1000
apart from each other. The driver only contains definitions for PM0

net: enetc: parameterize port MAC stats to also cover the pMAC

The ENETC has counters for the eMAC and for the pMAC exactly 0x1000
apart from each other. The driver only contains definitions for PM0,
the eMAC.

Rather than duplicating everything for PM1, modify the register
definitions such that they take the MAC as argument.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: ethernet: move from strlcpy with unused retval to strscpy

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Gen

net: ethernet: move from strlcpy with unused retval to strscpy

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Generated by a coccinelle script.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Petr Machata <petrm@nvidia.com> # For drivers/net/ethernet/mellanox/mlxsw
Acked-by: Geoff Levand <geoff@infradead.org> # For ps3_gelic_net and spider_net_ethtool
Acked-by: Tom Lendacky <thomas.lendacky@amd.com> # For drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c
Acked-by: Marcin Wojtas <mw@semihalf.com> # For drivers/net/ethernet/marvell/mvpp2
Reviewed-by: Leon Romanovsky <leonro@nvidia.com> # For drivers/net/ethernet/mellanox/mlx{4|5}
Reviewed-by: Shay Agroskin <shayagr@amazon.com> # For drivers/net/ethernet/amazon/ena
Acked-by: Krzysztof Hałasa <khalasa@piap.pl> # For IXP4xx Ethernet
Link: https://lore.kernel.org/r/20220830201457.7984-3-wsa+renesas@sang-engineering.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: count the tc-taprio window drops

The enetc scheduler for IEEE 802.1Qbv has 2 options (depending on
PTGCR[TG_DROP_DISABLE]) when we attempt to send an oversized packet
which will never fi

net: enetc: count the tc-taprio window drops

The enetc scheduler for IEEE 802.1Qbv has 2 options (depending on
PTGCR[TG_DROP_DISABLE]) when we attempt to send an oversized packet
which will never fit in its allotted time slot for its traffic class:
either block the entire port due to head-of-line blocking, or drop the
packet and set a bit in the writeback format of the transmit buffer
descriptor, allowing other packets to be sent.

We obviously choose the second option in the driver, but we do not
detect the drop condition, so from the perspective of the network stack,
the packet is sent and no error counter is incremented.

This change checks the writeback of the TX BD when tc-taprio is enabled,
and increments a specific ethtool statistics counter and a generic
"tx_dropped" counter in ndo_get_stats64.

Signed-off-by: Po Liu <Po.Liu@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net: enetc: report software timestamping via SO_TIMESTAMPING

Let user space properly determine that the enetc driver provides
software timestamps.

Fixes: 4caefbce06d1 ("enetc: add software timestam

net: enetc: report software timestamping via SO_TIMESTAMPING

Let user space properly determine that the enetc driver provides
software timestamps.

Fixes: 4caefbce06d1 ("enetc: add software timestamping")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20220324161210.4122281-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

ethtool: extend ringparam setting/getting API with rx_buf_len

Add two new parameters kernel_ringparam and extack for
.get_ringparam and .set_ringparam to extend more ring params
through netlink.

Si

ethtool: extend ringparam setting/getting API with rx_buf_len

Add two new parameters kernel_ringparam and extack for
.get_ringparam and .set_ringparam to extend more ring params
through netlink.

Signed-off-by: Hao Chen <chenhao288@hisilicon.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net: enetc: fix ethtool counter name for PM0_TERR

There are two counters named "MAC tx frames", one of them is actually
incorrect. The correct name for that counter should be "MAC tx error
frames",

net: enetc: fix ethtool counter name for PM0_TERR

There are two counters named "MAC tx frames", one of them is actually
incorrect. The correct name for that counter should be "MAC tx error
frames", which is symmetric to the existing "MAC rx error frames".

Fixes: 16eb4c85c964 ("enetc: Add ethtool statistics")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: <Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20211020165206.1069889-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

ethtool: extend coalesce setting uAPI with CQE mode

In order to support more coalesce parameters through netlink,
add two new parameter kernel_coal and extack for .set_coalesce
and .get_coalesce, th

ethtool: extend coalesce setting uAPI with CQE mode

In order to support more coalesce parameters through netlink,
add two new parameter kernel_coal and extack for .set_coalesce
and .get_coalesce, then some extra info can return to user with
the netlink API.

Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: enetc: add support for flow control

In the ENETC receive path, a frame received by the MAC is first stored
in a 256KB 'FIFO' memory, then transferred to DRAM when enqueuing it to
the RX ring. T

net: enetc: add support for flow control

In the ENETC receive path, a frame received by the MAC is first stored
in a 256KB 'FIFO' memory, then transferred to DRAM when enqueuing it to
the RX ring. The FIFO is a shared resource for all ENETC ports, but
every port keeps track of its own memory utilization, on RX and on TX.

There is a setting for RX rings through which they can either operate in
'lossy' mode (where the lack of a free buffer causes an immediate
discard of the frame) or in 'lossless' mode (where the lack of a free
buffer in the ring makes the frame stay longer in the FIFO).

In turn, when the memory utilization of the FIFO exceeds a certain
margin, the MAC can be configured to emit PAUSE frames.

There is enough FIFO memory to buffer up to 3 MTU-sized frames per RX
port while not jeopardizing the other use cases (jumbo frames), and
also not consume bytes from the port TX allocations. Also, 3 MTU-sized
frames worth of memory is enough to ensure zero loss for 64 byte packets
at 1G line rate.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

enetc: support PTP Sync packet one-step timestamping

This patch is to add support for PTP Sync packet one-step timestamping.
Since ENETC single-step register has to be configured dynamically per
pac

enetc: support PTP Sync packet one-step timestamping

This patch is to add support for PTP Sync packet one-step timestamping.
Since ENETC single-step register has to be configured dynamically per
packet for correctionField offeset and UDP checksum update, current
one-step timestamping packet has to be sent only when the last one
completes transmitting on hardware. So, on the TX, this patch handles
one-step timestamping packet as below:

- Trasmit packet immediately if no other one in transfer, or queue to
skb queue if there is already one in transfer.
The test_and_set_bit_lock() is used here to lock and check state.
- Start a work when complete transfer on hardware, to release the bit
lock and to send one skb in skb queue if has.

And the configuration for one-step timestamping on ENETC before
transmitting is,

- Set one-step timestamping flag in extension BD.
- Write 30 bits current timestamp in tstamp field of extension BD.
- Update PTP Sync packet originTimestamp field with current timestamp.
- Configure single-step register for correctionField offeset and UDP
checksum update.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net: enetc: add support for XDP_REDIRECT

The driver implementation of the XDP_REDIRECT action reuses parts from
XDP_TX, most notably the enetc_xdp_tx function which transmits an array
of TX software

net: enetc: add support for XDP_REDIRECT

The driver implementation of the XDP_REDIRECT action reuses parts from
XDP_TX, most notably the enetc_xdp_tx function which transmits an array
of TX software BDs. Only this time, the buffers don't have DMA mappings,
we need to create them.

When a BPF program reaches the XDP_REDIRECT verdict for a frame, we can
employ the same buffer reuse strategy as for the normal processing path
and for XDP_PASS: we can flip to the other page half and seed that to
the RX ring.

Note that scatter/gather support is there, but disabled due to lack of
multi-buffer support in XDP (which is added by this series):
https://patchwork.kernel.org/project/netdevbpf/cover/cover.1616179034.git.lorenzo@kernel.org/

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net: enetc: add support for XDP_TX

For reflecting packets back into the interface they came from, we create
an array of TX software BDs derived from the RX software BDs. Therefore,
we need to extend

net: enetc: add support for XDP_TX

For reflecting packets back into the interface they came from, we create
an array of TX software BDs derived from the RX software BDs. Therefore,
we need to extend the TX software BD structure to contain most of the
stuff that's already present in the RX software BD structure, for
reasons that will become evident in a moment.

For a frame with the XDP_TX verdict, we don't reuse any buffer right
away as we do for XDP_DROP (the same page half) or XDP_PASS (the other
page half, same as the skb code path).

Because the buffer transfers ownership from the RX ring to the TX ring,
reusing any page half right away is very dangerous. So what we can do is
we can recycle the same page half as soon as TX is complete.

The code path is:
enetc_poll
-> enetc_clean_rx_ring_xdp
-> enetc_xdp_tx
-> enetc_refill_rx_ring
(time passes, another MSI interrupt is raised)
enetc_poll
-> enetc_clean_tx_ring
-> enetc_recycle_xdp_tx_buff

But that creates a problem, because there is a potentially large time
window between enetc_xdp_tx and enetc_recycle_xdp_tx_buff, period in
which we'll have less and less RX buffers.

Basically, when the ship starts sinking, the knee-jerk reaction is to
let enetc_refill_rx_ring do what it does for the standard skb code path
(refill every 16 consumed buffers), but that turns out to be very
inefficient. The problem is that we have no rx_swbd->page at our
disposal from the enetc_reuse_page path, so enetc_refill_rx_ring would
have to call enetc_new_page for every buffer that we refill (if we
choose to refill at this early stage). Very inefficient, it only makes
the problem worse, because page allocation is an expensive process, and
CPU time is exactly what we're lacking.

Additionally, there is an even bigger problem: if we let
enetc_refill_rx_ring top up the ring's buffers again from the RX path,
remember that the buffers sent to transmission haven't disappeared
anywhere. They will be eventually sent, and processed in
enetc_clean_tx_ring, and an attempt will be made to recycle them.
But surprise, the RX ring is already full of new buffers, because we
were premature in deciding that we should refill. So not only we took
the expensive decision of allocating new pages, but now we must throw
away perfectly good and reusable buffers.

So what we do is we implement an elastic refill mechanism, which keeps
track of the number of in-flight XDP_TX buffer descriptors. We top up
the RX ring only up to the total ring capacity minus the number of BDs
that are in flight (because we know that those BDs will return to us
eventually).

The enetc driver manages 1 RX ring per CPU, and the default TX ring
management is the same. So we do XDP_TX towards the TX ring of the same
index, because it is affined to the same CPU. This will probably not
produce great results when we have a tc-taprio/tc-mqprio qdisc on the
interface, because in that case, the number of TX rings might be
greater, but I didn't add any checks for that yet (mostly because I
didn't know what checks to add).

It should also be noted that we need to change the DMA mapping direction
for RX buffers, since they may now be reflected into the TX ring of the
same device. We choose to use DMA_BIDIRECTIONAL instead of unmapping and
remapping as DMA_TO_DEVICE, because performance is better this way.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net: enetc: add support for XDP_DROP and XDP_PASS

For the RX ring, enetc uses an allocation scheme based on pages split
into two buffers, which is already very efficient in terms of preventing
reall

net: enetc: add support for XDP_DROP and XDP_PASS

For the RX ring, enetc uses an allocation scheme based on pages split
into two buffers, which is already very efficient in terms of preventing
reallocations / maximizing reuse, so I see no reason why I would change
that.

+--------+--------+--------+--------+--------+--------+--------+
| | | | | | | |
| half B | half B | half B | half B | half B | half B | half B |
| | | | | | | |
+--------+--------+--------+--------+--------+--------+--------+
| | | | | | | |
| half A | half A | half A | half A | half A | half A | half A | RX ring
| | | | | | | |
+--------+--------+--------+--------+--------+--------+--------+
^ ^
| |
next_to_clean next_to_alloc
next_to_use

+--------+--------+--------+--------+--------+
| | | | | |
| half B | half B | half B | half B | half B |
| | | | | |
+--------+--------+--------+--------+--------+--------+--------+
| | | | | | | |
| half B | half B | half A | half A | half A | half A | half A | RX ring
| | | | | | | |
+--------+--------+--------+--------+--------+--------+--------+
| | | ^ ^
| half A | half A | | |
| | | next_to_clean next_to_use
+--------+--------+
^
|
next_to_alloc

then when enetc_refill_rx_ring is called, whose purpose is to advance
next_to_use, it sees that it can take buffers up to next_to_alloc, and
it says "oh, hey, rx_swbd->page isn't NULL, I don't need to allocate
one!".

The only problem is that for default PAGE_SIZE values of 4096, buffer
sizes are 2048 bytes. While this is enough for normal skb allocations at
an MTU of 1500 bytes, for XDP it isn't, because the XDP headroom is 256
bytes, and including skb_shared_info and alignment, we end up being able
to make use of only 1472 bytes, which is insufficient for the default
MTU.

To solve that problem, we implement scatter/gather processing in the
driver, because we would really like to keep the existing allocation
scheme. A packet of 1500 bytes is received in a buffer of 1472 bytes and
another one of 28 bytes.

Because the headroom required by XDP is different (and much larger) than
the one required by the network stack, whenever a BPF program is added
or deleted on the port, we drain the existing RX buffers and seed new
ones with the required headroom. We also keep the required headroom in
rx_ring->buffer_offset.

The simplest way to implement XDP_PASS, where an skb must be created, is
to create an xdp_buff based on the next_to_clean RX BDs, but not clear
those BDs from the RX ring yet, just keep the original index at which
the BDs for this frame started. Then, if the verdict is XDP_PASS,
instead of converting the xdb_buff to an skb, we replay a call to
enetc_build_skb (just as in the normal enetc_clean_rx_ring case),
starting from the original BD index.

We would also like to be minimally invasive to the regular RX data path,
and not check whether there is a BPF program attached to the ring on
every packet. So we create a separate RX ring processing function for
XDP.

Because we only install/remove the BPF program while the interface is
down, we forgo the rcu_read_lock() in enetc_clean_rx_ring, since there
shouldn't be any circumstance in which we are processing packets and
there is a potentially freed BPF program attached to the RX ring.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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enetc: Fix reporting of h/w packet counters

Noticed some inconsistencies in packet statistics reporting.
This patch adds the missing Tx packet counter registers to
ethtool reporting and fixes the in

enetc: Fix reporting of h/w packet counters

Noticed some inconsistencies in packet statistics reporting.
This patch adds the missing Tx packet counter registers to
ethtool reporting and fixes the information strings for a
few of them.

Fixes: 16eb4c85c964 ("enetc: Add ethtool statistics")
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://lore.kernel.org/r/20201204171505.21389-1-claudiu.manoil@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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