linux-kernel - Re: [PATCH] net: stmmac: dwmac-qcom-ethqos: Configure host DMA width

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Date: Thu, 30 May 2024 08:00:58 -0500
From: Andrew Halaney <ahalaney@...hat.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Sagar Cheluvegowda <quic_scheluve@...cinc.com>, 
	Vinod Koul <vkoul@...nel.org>, Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Jose Abreu <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Jochen Henneberg <jh@...neberg-systemdesign.com>, linux-arm-msm@...r.kernel.org, netdev@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: stmmac: dwmac-qcom-ethqos: Configure host DMA width

On Thu, May 30, 2024 at 12:22:52AM GMT, Andrew Lunn wrote:
> On Wed, May 29, 2024 at 03:50:28PM -0500, Andrew Halaney wrote:
> > $Subject should be have [PATCH net] since this targets the net tree:
> > 
> > https://docs.kernel.org/process/maintainer-netdev.html
> > 
> > On Wed, May 29, 2024 at 11:39:04AM GMT, Sagar Cheluvegowda wrote:
> > > Fixes: 070246e4674b ("net: stmmac: Fix for mismatched host/device DMA address width")
> > > Signed-off-by: Sagar Cheluvegowda <quic_scheluve@...cinc.com>
> 
> > Also, I think the Fixes: here would be for adding support for this SoC
> > in the driver, not what's listed? Might make more sense after you have a
> > proper body though.
> 
> This is a tricky one. 
> 
> Fixes: 070246e4674b ("net: stmmac: Fix for mismatched host/device DMA
> address width") is when support for different DMA address widths was
> added. This fix cannot easily be back ported past that.
> 
> 070246e4674b first appears in v6.3-rc4.
> 
> dwmac-qcom-ethqos.c first appears in v5.1-rc1. However, Qualcomm did
> not start hacking on it until v6.7-rc6. It is unclear to me without a
> deep dive when Qualcomm actually started using this driver.
> 
> We might actually be looking at this the wrong way, and should in fact
> be looking at when a DT patch was added that made use of the driver,
> not the driver itself. If it was not used, it cannot be broken....
> 

I should have been more specific, sorry.

I think this should be:

    Fixes: 8c4d92e82d500 ("net: stmmac: dwmac-qcom-ethqos: add support for emac4 on sa8775p platforms")

Which appears after 070246e4674b ("net: stmmac: Fix for mismatched host/device DMA address width").

Reason being that specifically Sagar's patch is indicating that for the
SoC's/compatibles that currently use emac_v4_0_0_data structure, the DMA
address width needs to be specified.

If we were modifying structs that were added prior to 070246e4674b then
I agree, but at least the change as is I think could indicate the above
Fixes.

Thanks,
Andrew