netdev - Re: [PATCH net] Revert "net: stmmac: Specify hardware capability value when FIFO size isn't specified"

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Message-ID: <Z6STSb0ZSKN1e1rX@shell.armlinux.org.uk>
Date: Thu, 6 Feb 2025 10:47:37 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.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>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net] Revert "net: stmmac: Specify hardware capability
 value when FIFO size isn't specified"

On Thu, Feb 06, 2025 at 09:08:10AM +0100, Paolo Abeni wrote:
> On 2/5/25 1:57 PM, Russell King (Oracle) wrote:
> > This reverts commit 8865d22656b4, which caused breakage for platforms
> > which are not using xgmac2 or gmac4. Only these two cores have the
> > capability of providing the FIFO sizes from hardware capability fields
> > (which are provided in priv->dma_cap.[tr]x_fifo_size.)
> > 
> > All other cores can not, which results in these two fields containing
> > zero. We also have platforms that do not provide a value in
> > priv->plat->[tr]x_fifo_size, resulting in these also being zero.
> > 
> > This causes the new tests introduced by the reverted commit to fail,
> > and produce e.g.:
> > 
> > 	stmmaceth f0804000.eth: Can't specify Rx FIFO size
> > 
> > An example of such a platform which fails is QEMU's npcm750-evb.
> > This uses dwmac1000 which, as noted above, does not have the capability
> > to provide the FIFO sizes from hardware.
> > 
> > Therefore, revert the commit to maintain compatibility with the way
> > the driver used to work.
> > 
> > Reported-by: Guenter Roeck <linux@...ck-us.net>
> > Link: https://lore.kernel.org/r/4e98f967-f636-46fb-9eca-d383b9495b86@roeck-us.net
> > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> 
> Given the fallout caused by the blamed commit, the imminent net PR, and
> the substantial agreement about the patch already shared by many persons
> on the ML, unless someone raises very serious concerns very soon, I'm
> going to apply this patch (a little) earlier than the 24h grace period,
> to fit the mentioned PR.

Thanks. Here's the missing Fixes tag that I missed:

Fixes: 8865d22656b4 ("net: stmmac: Specify hardware capability value when
FIFO size isn't specified")

Not sure if patchwork will pick that up.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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