Re: [PATCH net v4 3/3] net: stmmac: Specify hardware capability value when FIFO size isn't specified

[Guenter Roeck]

On 2/1/25 12:35, Russell King (Oracle) wrote:
> On Sat, Feb 01, 2025 at 11:14:41AM -0800, Guenter Roeck wrote:
> > Hi,
> >
> > On Mon, Jan 27, 2025 at 10:38:20AM +0900, Kunihiko Hayashi wrote:
> > > When Tx/Rx FIFO size is not specified in advance, the driver checks if
> > > the value is zero and sets the hardware capability value in functions
> > > where that value is used.
> > >
> > > Consolidate the check and settings into function stmmac_hw_init() and
> > > remove redundant other statements.
> > >
> > > If FIFO size is zero and the hardware capability also doesn't have upper
> > > limit values, return with an error message.
> > >
> > > Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
> >
> > This patch breaks qemu's stmmac emulation, for example for
> > npcm750-evb. The error message is:
> > 	stmmaceth f0804000.eth: Can't specify Rx FIFO size
>
> Interesting. I looked at QEMU to see whether anything in the Debian
> stable version of QEMU might possibly have STMMAC emulation, but
> drew a blank... Even trying to find where in QEMU it emulates the
> STMMAC. I do see that it does include this, so maybe I can use that
> to test some of my stmmac changes. Thanks!

Support was added in qemu v9.0.0. See qemu commit 08f787a34c
("hw/net: Add NPCMXXX GMAC device"). It doesn't directly say what
the emulated hardware actually is, but the commit message says

    The following message shows up with the change:
    Broadcom BCM54612E stmmac-0:00: attached PHY driver [Broadcom BCM54612E] (mii_bus:phy_addr=stmmac-0:00, irq=POLL)
    stmmaceth f0802000.eth eth0: Link is Up - 1Gbps/Full - flow control rx/tx

so that is a bit of a hint.

Guenter