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This switch implements Hold/Release in a strange way, with no control
from the user as required by IEEE 802.1Q-2018 through Set-And-Hold-MAC
and Set-And-Release-MAC, but rather, it emits HOLD requests implicitly
based on the schedule.
Namely, when the gate of a preemptible TC is about to close (actually
QSYS::PREEMPTION_CFG.HOLD_ADVANCE octet times in advance of this event),
the QSYS seems to emit a HOLD request pulse towards the MAC which
preempts the currently transmitted packet, and further packets are held
back in the queue system.
This allows large frames to be squeezed through small time slots,
because HOLD requests initiated by the gate events result in the frame
being segmented in multiple fragments, the bit time of which is equal to
the size of the time slot.
It has been reported that the vsc9959_tas_guard_bands_update() logic
breaks this, because it doesn't take preemptible TCs into account, and
enables oversized frame dropping when the time slot doesn't allow a full
MTU to be sent, but it does allow 2*minFragSize to be sent (128B).
Packets larger than 128B are dropped instead of being sent in multiple
fragments.
Confusingly, the manual says:
| For guard band, SDU calculation of a traffic class of a port, if
| preemption is enabled (through 'QSYS::PREEMPTION_CFG.P_QUEUES') then
| QSYS::PREEMPTION_CFG.HOLD_ADVANCE is used, otherwise
| QSYS::QMAXSDU_CFG_*.QMAXSDU_* is used.
but this only refers to the static guard band durations, and the
QMAXSDU_CFG_* registers have dual purpose - the other being oversized
frame dropping, which takes place irrespective of whether frames are
preemptible or express.
So, to fix the problem, we need to call vsc9959_tas_guard_bands_update()
from ocelot_port_update_active_preemptible_tcs(), and modify the guard
band logic to consider a different (lower) oversize limit for
preemptible traffic classes.
Fixes: 403ffc2c34de ("net: mscc: ocelot: add support for preemptible traffic classes")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Message-ID: <20230705104422.49025-4-vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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In a future commit we will have to call vsc9959_tas_guard_bands_update()
from ocelot_port_update_active_preemptible_tcs(), and that will be
impossible due to the AB/BA locking dependencies between
ocelot->tas_lock and ocelot->fwd_domain_lock.
Just like we did in commit 3ff468ef987e ("net: mscc: ocelot: remove
struct ocelot_mm_state :: lock"), the only solution is to expand the
scope of ocelot->fwd_domain_lock for it to also serialize changes made
to the Time-Aware Shaper, because those will have to result in a
recalculation of cut-through TCs, which is something that depends on the
forwarding domain.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Message-ID: <20230705104422.49025-2-vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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In order to not transmit (preemptible) frames which will be received by
the link partner as corrupted (because it doesn't support FP), the
hardware requires the driver to program the QSYS_PREEMPTION_CFG_P_QUEUES
register only after the MAC Merge layer becomes active (verification
succeeds, or was disabled).
There are some cases when FP is known (through experimentation) to be
broken. Give priority to FP over cut-through switching, and disable FP
for known broken link modes.
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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ocelot_mm_update_port_status() updates mm->verify_status, but when the
verification state of a port changes, an IRQ isn't emitted, but rather,
only when the verification state reaches one of the final states (like
DISABLED, FAILED, SUCCEEDED) - things that would affect mm->tx_active,
which is what the IRQ *is* actually emitted for.
That is to say, user space may miss reports of an intermediary MAC Merge
verification state (like from INITIAL to VERIFYING), unless there was an
IRQ notifying the driver of the change in mm->tx_active as well.
This is not a huge deal, but for reliable reporting to user space, let's
call ocelot_mm_update_port_status() synchronously from
ocelot_port_get_mm(), which makes user space see the current MM status.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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The MAC Merge IRQ of all ports is shared with the PTP TX timestamp IRQ
of all ports, which means that currently, when a PTP TX timestamp is
generated, felix_irq_handler() also polls for the MAC Merge layer status
of all ports, looking for changes. This makes the kernel do more work,
and under certain circumstances may make ptp4l require a
tx_timestamp_timeout argument higher than before.
Changes to the MAC Merge layer status are only to be expected under
certain conditions - its TX direction needs to be enabled - so we can
check early if that is the case, and omit register access otherwise.
Make ocelot_mm_update_port_status() skip register access if
mm->tx_enabled is unset, and also call it once more, outside IRQ
context, from ocelot_port_set_mm(), when mm->tx_enabled transitions from
true to false, because an IRQ is also expected in that case.
Also, a port may have its MAC Merge layer enabled but it may not have
generated the interrupt. In that case, there's no point in writing to
DEV_MM_STATUS to acknowledge that IRQ. We can reduce the number of
register writes per port with MM enabled by keeping an "ack" variable
which writes the "write-one-to-clear" bits. Those are 3 in number:
PRMPT_ACTIVE_STICKY, UNEXP_RX_PFRM_STICKY and UNEXP_TX_PFRM_STICKY.
The other fields in DEV_MM_STATUS are read-only and it doesn't matter
what is written to them, so writing zero is just fine.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Unfortunately, the workarounds for the hardware bugs make it pointless
to keep fine-grained locking for the MAC Merge state of each port.
Our vsc9959_cut_through_fwd() implementation requires
ocelot->fwd_domain_lock to be held, in order to serialize with changes
to the bridging domains and to port speed changes (which affect which
ports can be cut-through). Simultaneously, the traffic classes which can
be cut-through cannot be preemptible at the same time, and this will
depend on the MAC Merge layer state (which changes from threaded
interrupt context).
Since vsc9959_cut_through_fwd() would have to hold the mm->lock of all
ports for a correct and race-free implementation with respect to
ocelot_mm_irq(), in practice it means that any time a port's mm->lock is
held, it would potentially block holders of ocelot->fwd_domain_lock.
In the interest of simple locking rules, make all MAC Merge layer state
changes (and preemptible traffic class changes) be serialized by the
ocelot->fwd_domain_lock.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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When the switch emits an IRQ, we don't know what caused it, and we
iterate through all ports to check the MAC Merge status.
Move that iteration inside the ocelot lib; we will change the locking in
a future change and it would be good to encapsulate that lock completely
within the ocelot lib.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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We don't read the verify_enabled variable from hardware in the MAC Merge
layer state GET operation, instead we always leave it set to "false".
The user may think something is wrong if they set verify_enabled to
true, then read it back and see it's still false, even though the
configuration took place.
Fixes: 6505b6805655 ("net: mscc: ocelot: add MAC Merge layer support for VSC9959")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230123184538.3420098-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Felix (VSC9959) has a DEV_GMII:MM_CONFIG block composed of 2 registers
(ENABLE_CONFIG and VERIF_CONFIG). Because the MAC Merge statistics and
pMAC statistics are already in the Ocelot switch lib even if just Felix
supports them, I'm adding support for the whole MAC Merge layer in the
common Ocelot library too.
There is an interrupt (shared with the PTP interrupt) which signals
changes to the MM verification state. This is done because the
preemptible traffic classes should be committed to hardware only once
the verification procedure has declared the link partner of being
capable of receiving preemptible frames.
We implement ethtool getters and setters for the MAC Merge layer state.
The "TX enabled" and "verify status" are taken from the IRQ handler,
using a mutex to ensure serialized access.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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