[U-Boot-Board-Maintainers] Raspberry pi 4 - u-boot - genet / scb

From: Andre Przywara <andre.przywara@arm.com>
To: u-boot@lists.denx.de
Subject: [U-Boot-Board-Maintainers] Raspberry pi 4 - u-boot - genet / scb
Date: Thu, 12 Dec 2019 18:38:29 +0000	[thread overview]
Message-ID: <20191212183829.1ab3fdf6@donnerap.cambridge.arm.com> (raw)
In-Reply-To: <02f18c7a-08cd-c5e8-164a-14dd9e472b6c@gmail.com>

On Thu, 12 Dec 2019 10:13:27 -0800
Florian Fainelli <f.fainelli@gmail.com> wrote:

Hi Florian,

thanks for chiming in!

> On 12/12/19 3:59 AM, Matthias Brugger wrote:
> > 
> > 
> > On 12/12/2019 11:41, Andre Przywara wrote:  
> >> On Wed, 11 Dec 2019 10:23:16 +0100
> >> Matthias Brugger <matthias.bgg@gmail.com> wrote:
> >>
> >> Hi,
> >>  
> >>> On 09/12/2019 14:33, Sascha Dewald wrote:  
> >>>> Hello Amit,
> >>>>
> >>>> no problem.
> >>>>
> >>>> Is there some git feature branch, to have a look ?    
> >>>
> >>> Yes I'd love to have a look as well :)  
> >>
> >> We will send an RFC later this week, Amit is doing some cleanup now. At the moment transfers work up to 256 packets (375KB when using TFTP), at this point it breaks, because recycling DMA descriptors is not working for some reason. I haven't found any documentation for the MAC, so I am reverse engineering the Linux driver and doing printf and tcpdump debugging right now. Looking forward to people joining us in this effort ;-)
> >>  
> > 
> > Thanks for the update. I CC'ed Florian who I think is the SW expert on that
> > chip. Maybe he can help you.  
> 
> Transfers work for up to 256 packets in which direction? Are you
> properly consuming descriptors that were produced by the RDMA (on
> receive), 

Yes, not sure we do it properly, but we do.

The problem I see is that the TDMA_CONS_INDEX does not increase after it reaches 256, although RDMA_PROD_INDEX does. Is there any cleanup in the actual descriptors needed?
Did I get this right that those indices are just linear "progress counters", and not actual descriptor indices? I see the Linux code masks them with 0xffff, not with the number of descriptors.

Will try to dig a bit deeper on this.

> conversely, polling the TDMA consumer index on transmit?

Yes, I switched over to that (from polling for the DMA_OWN bit).

> Can you share your code somewhere so I could see if there are obvious problems?

Of course, we just need to clean it up a bit, and it's getting late for Amit today. We will CC: you on the post tomorrow.

Thanks for you help!

Cheers,
Andre.