Re: [PATCH 3/5] net: cadence: macb: implement EEE TX LPI support

[Nicolai Buchwitz <nb@tipi-net.de>]

On 26.2.2026 10:52, Théo Lebrun wrote:
> On Wed Feb 25, 2026 at 6:50 PM CET, Russell King (Oracle) wrote:
>> On Wed, Feb 25, 2026 at 06:42:08PM +0100, Théo Lebrun wrote:
>>> On Wed Feb 25, 2026 at 10:15 AM CET, Nicolai Buchwitz wrote:
>>> > @@ -2349,6 +2454,8 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
>>> >  	netdev_tx_sent_queue(netdev_get_tx_queue(bp->dev, queue_index),
>>> >  			     skb->len);
>>> >
>>> > +	macb_tx_lpi_wake(bp);
>>> 
>>> Should this be protected by a bp->eee_active condition? It could go
>>> in macb_tx_lpi_wake(). We avoid a spinlock acquire per xmit for most
>>> platforms. Probably negligeable though.
>> 
>> It will read the register, find the bit clear, and then return if
>> EEE is already disabled.
> 
> Yes I agree with your sentence, sorry my point was unclear. I was not
> describing a bug but rather a performance optimisation.
> 
> We would look up bp->eee_active to know if we can avoid calling
> macb_tx_lpi_set(), to avoid grabbing bp->lock once per xmit.
> That spinlock is interface-wide.

So you're suggesting to revert to the v2 approach?
https://patchwork.kernel.org/project/netdevbpf/patch/20260224091821.47671-4-nb@tipi-net.de/
> 
> Thanks,
> 
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

Nicolai