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

[Jonas Rebmann <jre@pengutronix.de>]

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

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