netdev - Re: [PATCH] net: fec: allow disable coalescing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f2647407-3de0-4afd-bc79-5b58e13f10aa@pengutronix.de>
Date: Thu, 26 Jun 2025 10:33:51 +0200
From: Jonas Rebmann <jre@...gutronix.de>
To: Andrew Lunn <andrew@...n.ch>, Wei Fang <wei.fang@....com>
Cc: "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "kernel@...gutronix.de" <kernel@...gutronix.de>,
 Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....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>
Subject: Re: [PATCH] net: fec: allow disable coalescing

Hi Andrew,

On 2025-06-26 10:12, Andrew Lunn wrote:
> On Thu, Jun 26, 2025 at 02:36:37AM +0000, Wei Fang wrote:
>>>
>>> -       /* Must be greater than zero to avoid unpredictable behavior */
>>> -       if (!fep->rx_time_itr || !fep->rx_pkts_itr ||
>>> -           !fep->tx_time_itr || !fep->tx_pkts_itr)
>>> -               return;
> 
> Hi Wei
> 
> When i see a comment like this being removed, i wounder if there is
> any danger of side effects? Do you know what is being done here is
> actually safe, for all the different versions of the FEC which support
> coalescence?

For reference, this comment is taken in plain from section 11.6.4.1.16.3
in the i.MX 8M Plus Applications Processor Reference Manual (and is the
same for the 6UL).

I was also worried about this so I made sure that in any case where
either of those is zero, the coalescing enable bit (FEC_ITR_EN) is
explicitly disabled.

fec_enet_itr_coal_set is only ever called if FEC_QUIRK_HAS_COALESCE is
set and for those models, we expect disabling coalescing via FEC_ITR_EN
-- and consequently also setting the parameters to zero -- to be
unproblematic. This is also the reset default.

Regards,
Jonas

-- 
Pengutronix e.K.                           | Jonas Rebmann               |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |