[PATCH net-next v5 0/3] net: macb: implement ethtool set channels count operation

Add support for changing the active number of queues. Tested on Mobileye
EyeQ5. I had stalled this series, focusing on other topics. It is time
to bring it up to date and gather reviews.

I am posting this while the context-swapping series is in the mailing
lists as well; context-swapping should land first then we'll care about
set_channels. Why we want set_channels:
 - To reduce the memory usage of too many queues.
 - It makes sense to have before XDP, which is per-queue. In particular
   testing is simpler.

Have a nice day,
Thanks,
Théo

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
Changes in v5:
- New patch: add missing MACB_CAPS_QUEUE_DISABLE to 3 compatibles based
  on publicly available datasheets. That means they can benefit from
  the set_channels implementation.
- set_channels patch:
  - Refuse set_channels if it disables a queue with active TAPRIO.
  - Use TBQP.QUEUE_DISABLE bit to also disable transmit; previously we
    only disabled the receive engine.
  - Migrate code to newly introduced macb_queue_isr_clear() helper.
  - Adapt to newly introduced macb_quiesce_start(), where we want to
    synchronize_irq() on all queues, even the disabled ones.
  - IRQ handler now self-disarms on disabled queues.
  - Drop `old_count` unused stack variable.
  - Only allow TAPRIO rules on active queues.
  - Fix comments style and text in macb_set_channels(); in particular
    mention we'll use context-swapping once it is available.
- Distribute SRAM segments patch:
  - Introduce GEM_TXQSEGALLOC_MASK(q) and use field_prep|get() macros.
  - Introduce capability for this feature, as many publicly available
    GEM datasheets don't document the registers.
  - Remove upper register support. Lower register is enough to handle 8
    queues, which is the max we support.
  - Add edge case kunit for num_segments=128.
  - Introduce static_assert(MACB_MAX_QUEUES == 8) in
    gem_sram_distribute_segments() to signal that code will need
    updating if/when the constant changes.
- Update To/Cc list: drop Nicolas and Claudiu, add Conor and Nicolai.
- Rebase onto latest net-next/main (6b3e73774815).
- Link to v4: https://patch.msgid.link/20260317-macb-set-channels-v4-0-1bd4f4ffcfca@bootlin.com (local)

Changes in v4:
- macb_set_channels(): drop `count == old_count` check, it is redundant
  with both netlink and ioctl codepaths. See early returns in
  ethnl_set_channels() and ethtool_set_channels(). Discussion @ V2.
- Rebase to latest net-next (8737d7194d6d); nothing to report.
- Link to v3: https://patch.msgid.link/20260313-macb-set-channels-v3-0-c66b7781ddb8@bootlin.com (local)

Changes in v3:
- Makefile: fix compilation of kunit tests. This bug was hidden before
  because everything was builtin so it ended up linked together anyway.
  Now macb.o is the amalgation of macb_{main,ptp,utils}.o and
  macb_test.o is the amalgation of macb_{kunit,utils}.o.
- Kconfig CONFIG_MACB_KUNIT_TEST entry:
  - Turn into tristate; no good reason to restrict to bool.
  - Drop "depends on MACB". We do not need to compile the full MACB
    driver to test gem_sram_distribute_segments().
- Add usual MODULE_*() macros to macb_kunit.c.
- Drop unused init value of `ret` in macb_set_channels().
- Rebase to latest net-next; nothing to report.
- Link to v2: https://patch.msgid.link/20260311-macb-set-channels-v2-0-982693a1f5fc@bootlin.com (local)

Changes in v2:
- Move gem_sram_distribute_segments() from macb_main.c to macb_utils.c
  and kunit tests from macb_main.c to macb_kunit.c.
- macb_set_channels():
  - Add comment about MACB_CAPS_QUEUE_DISABLE.
  - Refuse operation if netif_running(), with code comment.
  - Drop useless sanity checks on ch->{combined,rx,tx}_count.
- Add help text to CONFIG_MACB_KUNIT_TEST.
- Fix `checkpatch --max-line-length=80` warnings.
- Rebase onto latest net-next; nothing to report.
- Link to v1: https://lore.kernel.org/r/20260305-macb-set-channels-v1-0-28e3a96a3dc3@bootlin.com (local)

---
Théo Lebrun (3):
      net: macb: add QUEUE_DISABLE capability to 3 compatibles
      net: macb: implement ethtool_ops.get|set_channels()
      net: macb: distribute evenly Tx SRAM segments

 drivers/net/ethernet/cadence/Kconfig      |  12 +++
 drivers/net/ethernet/cadence/Makefile     |   5 +-
 drivers/net/ethernet/cadence/macb.h       |  20 +++++
 drivers/net/ethernet/cadence/macb_kunit.c |  78 +++++++++++++++++
 drivers/net/ethernet/cadence/macb_main.c  | 135 +++++++++++++++++++++++++-----
 drivers/net/ethernet/cadence/macb_utils.c |  60 +++++++++++++
 6 files changed, 287 insertions(+), 23 deletions(-)
---
base-commit: 6b3e73774815910a39d8ca75b9ad7df963f61d50
change-id: 20260305-macb-set-channels-5bf6e07f3270

Best regards,
--  
Théo Lebrun [off-list ref]