linux-kernel - Re: [PATCH v1] sun4i-emac.c: enable emac tx dma

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Date:   Sun, 9 Jan 2022 21:45:01 +0100
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     conleylee@...mail.com
Cc:     davem@...emloft.net, mripard@...nel.org, wens@...e.org,
        jernej.skrabec@...il.com, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] sun4i-emac.c: enable emac tx dma

Le Sun, Jan 09, 2022 at 05:17:55PM +0800, conleylee@...mail.com a écrit :
> From: conley <conleylee@...mail.com>
> 
> Hello
> I am reading the R40 user manual and trying to create a new path to enable
> emac tx dma channel. According to the figure 8-21(TX Operation Diagram),
> I try to enable emac tx dma channel by the follow steps:
> 1. enable tx dma mode
> 2. set packet lengths
> 2. move data from skb to tx fifo by using dma in xmit function.
> 3. start transfer from tx fifo to phy in dma tx done callback
> 
> But it doesn't work. emac tx interrupt and dma finished interrupt are
> raised, but no packets are transmitted (I test it by tcpdump).
> Do you know how to configure the emac tx dma correctly? Thanks ~
> 

Hello

Here are my thoughts to help you:
- Your email is not a real patch, but an ask for help, so you should not use [ PATCH ] in the subject.
- If it was a patch, "v1" is not necessary
- Your patch below is doing too many unrelated different things, it is hard to see the DMA TX enable part
- I think you could first send a preliminary patch which adds all EMAC_INT_CTL_TX_xxx which are already used by the driver (to reduce the diff)
- Without the DTB change, it is hard to see the whole picture, did you correctly use the right dma number for an easy example.
- Knowing also the board (and so PHY, modes etc...) could help
- I think your priority should not to add TX, but to fix reported problems to your initial patch (build warnings/error https://marc.info/?l=linux-arm-kernel&m=164159846213585&w=2) since your work on TX will need to be applied after this.
- For the previous point, always build test with at least 2 different 32/64 arch. And if possible a total different arch (like x86_64).

Anyway, I will try to test your patch on my a10 board

Regards