linux-kernel - Re: [PATCH net-next v1] net: stmmac: TSO: Simplify the code flow of DMA descriptor allocations

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Message-ID: <20241217195454.000016ce@gmail.com>
Date: Tue, 17 Dec 2024 19:54:54 +0800
From: Furong Xu <0x1207@...il.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
 <joabreu@...opsys.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
 xfr@...look.com
Subject: Re: [PATCH net-next v1] net: stmmac: TSO: Simplify the code flow of
 DMA descriptor allocations

On Tue, 17 Dec 2024 10:30:24 +0100, Paolo Abeni <pabeni@...hat.com> wrote:

> On 12/13/24 04:00, Furong Xu wrote:
> > The DMA AXI address width of DWMAC cores can be configured to
> > 32-bit/40-bit/48-bit, then the format of DMA transmit descriptors
> > get a little different between 32-bit and 40-bit/48-bit.
> > Current driver code checks priv->dma_cap.addr64 to use certain format
> > with certain configuration.
> > 
> > This patch converts the format of DMA transmit descriptors on platforms
> > that the DMA AXI address width is configured to 32-bit (as described by
> > function comments of stmmac_tso_xmit() in current code) to a more generic
> > format (see the updated function comments after this patch) which is
> > actually already used on 40-bit/48-bit platforms to provide better
> > compatibility and make code flow cleaner.
> > 
> > Tested and verified on:
> > DWMAC CORE 5.10a with 32-bit DMA AXI address width
> > DWXGMAC CORE 3.20a with 40-bit DMA AXI address width
> > 
> > Signed-off-by: Furong Xu <0x1207@...il.com>  
> 
> Makes sense to me.
> 
> Since this could potentially impact multiple versions, it would be great
> if we could have a little more 3rd parties testing.

Totally agree.

Multiple devices with multiple versions of DWMAC core which is
configured to 32-bit DMA AXI address width seem to very hard to find
and test this patch :(

Jon Hunter @ NVIDIA has two versions of DWMAC cores different from mine,
Tegra186 Jetson TX2 (DWMAC CORE 4.10) and
Tegra194 Jetson AGX Xavier (DWMAC CORE 5.00),
but both of them are configured to 40-bit DMA AXI address width, this does
not match the case that this patch tries to convert. So I decided not to
request him to provide help.