[net-next PATCH] octeontx2-af: Workaround SQM/PSE stalls by disabling sticky

[net-next PATCH] octeontx2-af: Workaround SQM/PSE stalls by disabling sticky

[Geetha sowjanya]

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NIX SQ manager sticky mode is known to cause stalls when multiple SQs
share an SMQ and transmit concurrently. Additionally, PSE may deadlock
on transitions between sticky and non-sticky transmissions. There is
also a credit drop issue observed when certain condition clocks are
gated.

work around these hardware errata by:
- Disabling SQM sticky operation:
  - Clear TM6 (bit 15)
  - Clear TM11 (bit 14)
- Disabling sticky → non-sticky transition path that can deadlock PSE:
  - Clear TM5 (bit 23)
- Preventing credit drops by keeping the control-flow clock enabled:
  - Set TM9 (bit 21)

These changes are applied via NIX_AF_SQM_DBG_CTL_STATUS. With this
configuration the SQM/PSE maintain forward progress under load without
credit loss, at the cost of disabling sticky optimizations.

Signed-off-by: Geetha sowjanya <gakula@marvell.com>
---
 drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
index 2f485a930edd..9520a55cb710 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
@@ -4938,12 +4938,18 @@ static int rvu_nix_block_init(struct rvu *rvu, struct nix_hw *nix_hw)
 	/* Set chan/link to backpressure TL3 instead of TL2 */
 	rvu_write64(rvu, blkaddr, NIX_AF_PSE_CHANNEL_LEVEL, 0x01);
 
-	/* Disable SQ manager's sticky mode operation (set TM6 = 0)
+	/* Disable SQ manager's sticky mode operation (set TM6 = 0, TM11 = 0)
 	 * This sticky mode is known to cause SQ stalls when multiple
-	 * SQs are mapped to same SMQ and transmitting pkts at a time.
+	 * SQs are mapped to same SMQ and transmitting pkts simultaneously.
+	 * NIX PSE may deadlock when there are any sticky to non-sticky
+	 * transmission. Hence disable it (TM5 = 0).
 	 */
 	cfg = rvu_read64(rvu, blkaddr, NIX_AF_SQM_DBG_CTL_STATUS);
-	cfg &= ~BIT_ULL(15);
+	cfg &= ~(BIT_ULL(15) | BIT_ULL(14) | BIT_ULL(23));
+	/* NIX may drop credits when condition clocks are turned off.
+	 * Hence enable control flow clk (set TM9 = 1).
+	 */
+	cfg |= BIT_ULL(21);
 	rvu_write64(rvu, blkaddr, NIX_AF_SQM_DBG_CTL_STATUS, cfg);
 
 	ltdefs = rvu->kpu.lt_def;
-- 
2.25.1

Re: [net-next PATCH] octeontx2-af: Workaround SQM/PSE stalls by disabling sticky

[Simon Horman]

On Tue, Jan 27, 2026 at 06:21:47PM +0530, Geetha sowjanya wrote:
> NIX SQ manager sticky mode is known to cause stalls when multiple SQs
> share an SMQ and transmit concurrently. Additionally, PSE may deadlock
> on transitions between sticky and non-sticky transmissions. There is
> also a credit drop issue observed when certain condition clocks are
> gated.
> 
> work around these hardware errata by:
> - Disabling SQM sticky operation:
>   - Clear TM6 (bit 15)
>   - Clear TM11 (bit 14)
> - Disabling sticky → non-sticky transition path that can deadlock PSE:
>   - Clear TM5 (bit 23)
> - Preventing credit drops by keeping the control-flow clock enabled:
>   - Set TM9 (bit 21)
> 
> These changes are applied via NIX_AF_SQM_DBG_CTL_STATUS. With this
> configuration the SQM/PSE maintain forward progress under load without
> credit loss, at the cost of disabling sticky optimizations.
> 
> Signed-off-by: Geetha sowjanya <gakula@marvell.com>

I didn't look over the rest of the driver, but it strikes me that the code
touched by this patch could benefit from some defines for the bits of cfg.

But I don't think that needs to block progress of this patch.

Reviewed-by: Simon Horman <horms@kernel.org>

...

Re: [net-next PATCH] octeontx2-af: Workaround SQM/PSE stalls by disabling sticky

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 27 Jan 2026 18:21:47 +0530 you wrote:
> NIX SQ manager sticky mode is known to cause stalls when multiple SQs
> share an SMQ and transmit concurrently. Additionally, PSE may deadlock
> on transitions between sticky and non-sticky transmissions. There is
> also a credit drop issue observed when certain condition clocks are
> gated.
> 
> work around these hardware errata by:
> - Disabling SQM sticky operation:
>   - Clear TM6 (bit 15)
>   - Clear TM11 (bit 14)
> - Disabling sticky → non-sticky transition path that can deadlock PSE:
>   - Clear TM5 (bit 23)
> - Preventing credit drops by keeping the control-flow clock enabled:
>   - Set TM9 (bit 21)
> 
> [...]

Here is the summary with links:
  - [net-next] octeontx2-af: Workaround SQM/PSE stalls by disabling sticky
    https://git.kernel.org/netdev/net-next/c/70e9a5760abf

You are awesome, thank you!
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