From: Simon Horman <horms@kernel.org>
To: Daniel Machon <daniel.machon@microchip.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Steen Hegelund <Steen.Hegelund@microchip.com>,
UNGLinuxDriver@microchip.com, netdev@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: sparx5/lan969x: fix DWRR cost max to match hardware register width
Date: Thu, 12 Feb 2026 17:53:39 +0000 [thread overview]
Message-ID: <aY4TozfU1piv40Nh@horms.kernel.org> (raw)
In-Reply-To: <20260210-sparx5-fix-dwrr-cost-max-v1-1-58fbdbc25652@microchip.com>
On Tue, Feb 10, 2026 at 02:44:01PM +0100, Daniel Machon wrote:
> DWRR (Deficit Weighted Round Robin) scheduling distributes bandwidth
> across traffic classes based on per-queue cost values, where lower cost
> means higher bandwidth share.
>
> The SPX5_DWRR_COST_MAX constant is 63 (6 bits) but the hardware
> register field HSCH_DWRR_ENTRY_DWRR_COST is GENMASK(24, 20), only
> 5 bits wide (max 31). This causes sparx5_weight_to_hw_cost() to
> compute cost values that silently overflow via FIELD_PREP, resulting
> in incorrect scheduling weights.
>
> Set SPX5_DWRR_COST_MAX to 31 to match the hardware register width.
>
> Fixes: 211225428d65 ("net: microchip: sparx5: add support for offloading ets qdisc")
> Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2026-02-12 17:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-10 13:44 [PATCH net] net: sparx5/lan969x: fix DWRR cost max to match hardware register width Daniel Machon
2026-02-12 17:53 ` Simon Horman [this message]
2026-02-13 3:10 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aY4TozfU1piv40Nh@horms.kernel.org \
--to=horms@kernel.org \
--cc=Steen.Hegelund@microchip.com \
--cc=UNGLinuxDriver@microchip.com \
--cc=andrew+netdev@lunn.ch \
--cc=daniel.machon@microchip.com \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=kuba@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox