| From: |
| Théo Lebrun <theo.lebrun-AT-bootlin.com> |
| To: |
| Nicolas Ferre <nicolas.ferre-AT-microchip.com>, Claudiu Beznea <claudiu.beznea-AT-tuxon.dev>, Andrew Lunn <andrew+netdev-AT-lunn.ch>, "David S. Miller" <davem-AT-davemloft.net>, Eric Dumazet <edumazet-AT-google.com>, Jakub Kicinski <kuba-AT-kernel.org>, Paolo Abeni <pabeni-AT-redhat.com>, Richard Cochran <richardcochran-AT-gmail.com>, Russell King <linux-AT-armlinux.org.uk> |
| Subject: |
| [PATCH net-next 00/11] net: macb: implement context swapping |
| Date: |
| Wed, 01 Apr 2026 18:39:03 +0200 |
| Message-ID: |
| <20260401-macb-context-v1-0-9590c5ab7272@bootlin.com> |
| Cc: |
| Paolo Valerio <pvalerio-AT-redhat.com>, Conor Dooley <conor-AT-kernel.org>, Nicolai Buchwitz <nb-AT-tipi-net.de>, Vladimir Kondratiev <vladimir.kondratiev-AT-mobileye.com>, Gregory CLEMENT <gregory.clement-AT-bootlin.com>, Benoît Monin <benoit.monin-AT-bootlin.com>, Tawfik Bayouk <tawfik.bayouk-AT-mobileye.com>, Thomas Petazzoni <thomas.petazzoni-AT-bootlin.com>, Maxime Chevallier <maxime.chevallier-AT-bootlin.com>, netdev-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org, Théo Lebrun <theo.lebrun-AT-bootlin.com> |
| Archive-link: |
| Article |
MACB has a pretty primitive approach to buffer management. They are all
stored in `struct macb *bp`. On operations that require buffer realloc
(set_ringparam & change_mtu ATM), the only option is to close the
interface, change our global state and re-open the interface.
Two issues:
- It doesn't fly on memory pressured systems; we free our precious
buffers and don't manage to reallocate fully, meaning our machine
just lost its network access.
- Anecdotally, it is pretty slow because it implies a full PHY reinit.
Instead, we shall:
- allocate a new context (including buffers) first
- if it fails, early return without any impact to the interface
- stop interface
- update global state (bp, netdev, etc)
- pass newly allocated buffer pointers to the hardware
- start interface
- free old context
This is what we implement here. Both .set_ringparam() and
.ndo_change_mtu() are covered by this series. In the future,
at least .set_channels() [0], XDP [1] and XSK [2] would benefit.
The change is super intrusive so conflicts will be major. Sorry!
Thanks,
Have a nice day,
Théo
[0]: https://lore.kernel.org/netdev/20260317-macb-set-channels...
[1]: https://lore.kernel.org/netdev/20260323221047.2749577-1-p...
[2]: https://lore.kernel.org/netdev/20260304-macb-xsk-v1-0-ba2...
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
Théo Lebrun (11):
net: macb: unify device pointer naming convention
net: macb: unify `struct macb *` naming convention
net: macb: unify queue index variable naming convention and types
net: macb: enforce reverse christmas tree (RCT) convention
net: macb: allocate tieoff descriptor once across device lifetime
net: macb: introduce macb_context struct for buffer management
net: macb: avoid macb_init_rx_buffer_size() modifying state
net: macb: make `struct macb` subset reachable from macb_context struct
net: macb: introduce macb_context_alloc() helper
net: macb: use context swapping in .set_ringparam()
net: macb: use context swapping in .ndo_change_mtu()
drivers/net/ethernet/cadence/macb.h | 119 +-
drivers/net/ethernet/cadence/macb_main.c | 1731 +++++++++++++++++-------------
drivers/net/ethernet/cadence/macb_pci.c | 46 +-
drivers/net/ethernet/cadence/macb_ptp.c | 26 +-
4 files changed, 1090 insertions(+), 832 deletions(-)
---
base-commit: 321d1ee521de1362c22adadbc0ce066050a17783
change-id: 20260401-macb-context-bd0caf20414d
Best regards,
--
Théo Lebrun <theo.lebrun@bootlin.com>
