linux-kernel - Re: [PATCH net-next 2/2] net: stmmac: TBS support for platform driver

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Date: Thu, 11 Jan 2024 18:26:18 +0800
From: Rohan G Thomas <rohan.g.thomas@...el.com>
To: quic_abchauha@...cinc.com
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Subject: Re: [PATCH net-next 2/2] net: stmmac: TBS support for platform driver

On Wed, 10 Jan 2024 20:20:39 +0000 : Abhishek Chauhan (ABC) wrote:

> Qualcomm had similar discussions with respect to enabling of TBS for a
> particular queue.
> We had similar discussion on these terms yesterday with Redhat. Adding
> Andrew from Redhat here
> 
> What we discovered as part of the discussions is listed below.
> 
> 1. Today upstream stmmac code is designed in such a way that TBS flag is put
> as part of queue configurations(see below snippet) and as well know that
> stmmac queue configuration comes from the dtsi file.
> 
> //ndo_open => stmmac_open
> int tbs_en = priv->plat->tx_queues_cfg[chan].tbs_en;(comes from
> tx_queues_cfg)
> 
> /* Setup per-TXQ tbs flag before TX descriptor alloc */ tx_q->tbs |= tbs_en ?
> STMMAC_TBS_AVAIL : 0;
> 
> 2. There is a no way to do this dynamically from user space because we don't
> have any API exposed which can do it from user space and also TBS rely on
> special descriptors aka enhanced desc this cannot be done run time and
> stmmac has to be aware of it before we do DMA/MAC/MTL start. To do this
> dynamically would only mean stopping DMA/MAC/MTL realloc resources for
> enhanced desc and the starting MAC/DMA/MTL. This means we are disrupting
> other traffic(By stopping MAC block).
> 
> 3. I dont think there is a way we can enable this dynamically today. I would like
> upstream community to share your thoughts as well.
> 
> 4. I agree with Rohan's patch here and want upstream community to accept it.
> This will allow use to configure the queues where TBS needs to be enabled as
> hardcoding in the code unless upstream has better way to this using
> userspace.
> 
> Please let us know if you think otherwise.
> 
> 

Hi Abhishek,

Thanks for bringing this to discussion and a better explanation from
your side. I agree with you.

Best Regards,
Rohan