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

[nb@tipi-net.de]

On 23.2.2026 11:07, Russell King (Oracle) wrote:
> On Mon, Feb 23, 2026 at 10:04:10AM +0100, Nicolai Buchwitz wrote:
>> Implement software-managed TX Low Power Idle (LPI) for the Cadence GEM
>> MAC as part of IEEE 802.3az Energy Efficient Ethernet support.
>> 
>> The GEM MAC has no built-in idle timer - the TXLPIEN bit (NCR bit 19)
>> immediately asserts LPI and blocks all TX while set. The MAC does not
>> auto-wake for transmit. Per Microchip GMAC documentation (section
>> 40.6.19): "It is best to use firmware to control LPI."
>> 
>> This patch implements a software idle timer using delayed_work:
>> - On TX completion with an empty ring, schedule LPI entry after a
>>   configurable idle timeout (default 250ms). The work function
>>   verifies all TX queues are truly idle before entering LPI to
>>   prevent entering LPI while traffic is still active.
>> - On TX start, wake from LPI by clearing TXLPIEN, cancelling any
>>   pending re-entry, and waiting 50us for the PHY to exit LPI
>>   (conservative vs IEEE 802.3az Tw_sys of ~17us/~30us)
>> - On link up, check EEE negotiation via phy_init_eee() and defer
>>   first LPI entry by 1 second per IEEE 802.3az requirements
>> - On link down, immediately cancel pending work and clear TXLPIEN
>> 
>> The timer value is configurable at runtime via ethtool --set-eee
>> tx-timer.
>> 
>> The implementation is gated on MACB_CAPS_EEE so platforms must
>> explicitly opt in via their macb_config.
> 
> In addition to my comments, please check the nipabot status for this
> patch which can be found at:
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20260223090412.44070-4-nb@tipi-net.de/
> 

Thanks. I will have a look at the mentioned patches + feedback from the 
pipeline and prepare a v2 of this series.

> Thanks.

Nicolai