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Date: Thu, 20 Aug 2026 10:39:50 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Pavan Chebbi <pavan.chebbi@broadcom.com>
Cc: Thomas Walsh <thwalsh@redhat.com>, Michael Chan
 <michael.chan@broadcom.com>, Andrew Lunn <andrew+netdev@lunn.ch>, "David S.
 Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo
 Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, Michal Schmidt <mschmidt@redhat.com>
Subject: Re: [PATCH net] bnxt_en: Gate TPH enablement behind
 BNXT_SUPPORTS_QUEUE_API check
Message-ID: <20260820103950.5dfa2969@kernel.org>
In-Reply-To: <CALs4sv1zb7OemFcKRceoO49F8yPSOdZWSkomvU=mGmReR74=BA@mail.gmail.com>
References: <20260818141556.64303-1-thwalsh@redhat.com>
	<CALs4sv1zb7OemFcKRceoO49F8yPSOdZWSkomvU=mGmReR74=BA@mail.gmail.com>
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On Wed, 19 Aug 2026 15:18:49 +0530 Pavan Chebbi wrote:
> >         /* Enable TPH support as part of IRQ request */
> > -       rc = pcie_enable_tph(bp->pdev, PCI_TPH_ST_IV_MODE);
> > -       if (!rc)
> > -               bp->tph_mode = PCI_TPH_ST_IV_MODE;
> > +       if (BNXT_SUPPORTS_QUEUE_API(bp)) {  
> 
> IMO we should not gate pcie_enable_tph() on BNXT_SUPPORTS_QUEUE_API,
> since TPH's initial steering-tag placement is valid on its own and
> re-steering may never be needed in some cases?
> So in these cases it simply disables the feature.

Since irqs are requested at open wouldn't this mean that users who
program affinity (all serious users?) will have the wrong TPH? Which
is presumably worse than no TPH at all?

IMHO the simplicity and consistency is good. AFAIU queue API is
supported on fairly old bnxt NICs so the combination of CPU needing
TPH and NIC design being 15(?) years old is rather unlikely in the 
first place. The real scenario where users may run into no queue API
support is FW being old, in which case FW should be updated?