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Message-ID: <f2a8ede9-52fa-4f69-8ab2-3290171bc886@intel.com> Date: Thu, 27 Mar 2025 15:02:07 +0200 From: Mor Bar-Gabay <morx.bar.gabay@...el.com> To: Faizal Rahim <faizal.abdul.rahim@...ux.intel.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, Alexandre Torgue <alexandre.torgue@...s.st.com>, Simon Horman <horms@...nel.org>, Vladimir Oltean <vladimir.oltean@....com>, Russell King <linux@...linux.org.uk>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, Furong Xu <0x1207@...il.com>, Choong Yong Liang <yong.liang.choong@...ux.intel.com>, Russell King <rmk+kernel@...linux.org.uk>, Hariprasad Kelam <hkelam@...vell.com>, Xiaolei Wang <xiaolei.wang@...driver.com>, "Suraj Jaiswal" <quic_jsuraj@...cinc.com>, Kory Maincent <kory.maincent@...tlin.com>, Gal Pressman <gal@...dia.com>, Jesper Nilsson <jesper.nilsson@...s.com>, <linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>, <linux-stm32@...md-mailman.stormreply.com>, Chwee-Lin Choong <chwee.lin.choong@...el.com>, Vinicius Costa Gomes <vinicius.gomes@...el.com>, Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>, Serge Semin <fancer.lancer@...il.com> Subject: Re: [Intel-wired-lan] [PATCH iwl-next v10 10/14] igc: add support for frame preemption verification On 18/03/2025 5:07, Faizal Rahim wrote: > This patch implements the "ethtool --set-mm" callback to trigger the > frame preemption verification handshake. > > Uses the MAC Merge Software Verification (mmsv) mechanism in ethtool > to perform the verification handshake for igc. > The structure fpe.mmsv is set by mmsv in ethtool and should remain > read-only for the driver. > > Other mmsv callbacks: > a) configure_tx() -> not used yet at this point > - igc lacks registers to configure FPE in the transmit direction, so > this API is not utilized for now. When igc supports preemptible queue, > driver will use this API to manage its configuration. > > b) configure_pmac() -> not used > - this callback dynamically controls pmac_enabled at runtime. For > example, mmsv calls configure_pmac() and disables pmac_enabled when > the link partner goes down, even if the user previously enabled it. > The intention is to save power but it is not feasible in igc > because it causes an endless adapter reset loop: > > 1) Board A and Board B complete the verification handshake. Tx mode > register for both boards are in TSN mode. > 2) Board B link goes down. > > On Board A: > 3) mmsv calls configure_pmac() with pmac_enabled = false. > 4) configure_pmac() in igc updates a new field based on pmac_enabled. > Driver uses this field in igc_tsn_new_flags() to indicate that the > user enabled/disabled FPE. > 5) configure_pmac() in igc calls igc_tsn_offload_apply() to check > whether an adapter reset is needed. Calls existing logic in > igc_tsn_will_tx_mode_change() and igc_tsn_new_flags(). > 6) Since pmac_enabled is now disabled and no other TSN feature is > active, igc_tsn_will_tx_mode_change() evaluates to true because Tx > mode will switch from TSN to Legacy. > 7) Driver resets the adapter. > 8) Registers are set, and Tx mode switches to Legacy. > 9) When link partner is up, steps 3–8 repeat, but this time with > pmac_enabled = true, reactivating TSN. > igc_tsn_will_tx_mode_change() evaluates to true again, since Tx > mode will switch from Legacy to TSN. > 10) Driver resets the adapter. > 11) Adapter reset completes, registers are set, and Tx mode switches to > TSN. > > On Board B: > 12) Adapter reset on Board A at step 10 causes it to detect its link > partner as down. > 13) Repeats steps 3–8. > 14) Once reset adapter on Board A is completed at step 11, it detects > its link partner as up. > 15) Repeats steps 9–11. > > - this cycle repeats indefinitely. To avoid this issue, igc only uses > mmsv.pmac_enabled to track whether FPE is enabled or disabled. > > Co-developed-by: Vinicius Costa Gomes <vinicius.gomes@...el.com> > Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com> > Co-developed-by: Choong Yong Liang <yong.liang.choong@...ux.intel.com> > Signed-off-by: Choong Yong Liang <yong.liang.choong@...ux.intel.com> > Co-developed-by: Chwee-Lin Choong <chwee.lin.choong@...el.com> > Signed-off-by: Chwee-Lin Choong <chwee.lin.choong@...el.com> > Reviewed-by: Vladimir Oltean <vladimir.oltean@....com> > Signed-off-by: Faizal Rahim <faizal.abdul.rahim@...ux.intel.com> > --- > drivers/net/ethernet/intel/Kconfig | 1 + > drivers/net/ethernet/intel/igc/igc.h | 12 +- > drivers/net/ethernet/intel/igc/igc_base.h | 1 + > drivers/net/ethernet/intel/igc/igc_defines.h | 8 +- > drivers/net/ethernet/intel/igc/igc_ethtool.c | 21 +++ > drivers/net/ethernet/intel/igc/igc_main.c | 52 ++++++- > drivers/net/ethernet/intel/igc/igc_tsn.c | 146 ++++++++++++++++++- > drivers/net/ethernet/intel/igc/igc_tsn.h | 50 +++++++ > 8 files changed, 286 insertions(+), 5 deletions(-) > Tested-by: Mor Bar-Gabay <morx.bar.gabay@...el.com>
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