linux-kernel - Re: [PATCH net-next v4 1/2] net: stmmac: Refactor VLAN implementation

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Message-ID: <aAovTY6Q-4S__0Mh@shell.armlinux.org.uk>
Date: Thu, 24 Apr 2025 13:32:13 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Boon Khai Ng <boon.khai.ng@...era.com>, netdev@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, 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>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Furong Xu <0x1207@...il.com>,
	Matthew Gerlach <matthew.gerlach@...era.com>,
	Tien Sung Ang <tien.sung.ang@...era.com>,
	Mun Yew Tham <mun.yew.tham@...era.com>,
	G Thomas Rohan <rohan.g.thomas@...era.com>
Subject: Re: [PATCH net-next v4 1/2] net: stmmac: Refactor VLAN implementation

On Thu, Apr 24, 2025 at 02:04:04PM +0200, Paolo Abeni wrote:
> On 4/21/25 6:29 PM, Boon Khai Ng wrote:
> > Refactor VLAN implementation by moving common code for DWMAC4 and
> > DWXGMAC IPs into a separate VLAN module. VLAN implementation for
> > DWMAC4 and DWXGMAC differs only for CSR base address, the descriptor
> > for the VLAN ID and VLAN VALID bit field.
> > 
> > The descriptor format for VLAN is not moved to the common code due
> > to hardware-specific differences between DWMAC4 and DWXGMAC.
> > 
> > For the DWMAC4 IP, the Receive Normal Descriptor 0 (RDES0) is
> > formatted as follows:
> >     31                                                0
> >       ------------------------ -----------------------
> > RDES0| Inner VLAN TAG [31:16] | Outer VLAN TAG [15:0] |
> >       ------------------------ -----------------------
> > 
> > For the DWXGMAC IP, the RDES0 format varies based on the
> > Tunneled Frame bit (TNP):
> > 
> > a) For Non-Tunneled Frame (TNP=0)
> > 
> >     31                                                0
> >       ------------------------ -----------------------
> > RDES0| Inner VLAN TAG [31:16] | Outer VLAN TAG [15:0] |
> >       ------------------------ -----------------------
> > 
> > b) For Tunneled Frame (TNP=1)
> > 
> >      31                   8 7                3 2      0
> >       --------------------- ------------------ -------
> > RDES0| VNID/VSID           | Reserved         | OL2L3 |
> >       --------------------- ------------------ ------
> > 
> > The logic for handling tunneled frames is not yet implemented
> > in the dwxgmac2_wrback_get_rx_vlan_tci() function. Therefore,
> > it is prudent to maintain separate functions within their
> > respective descriptor driver files
> > (dwxgmac2_descs.c and dwmac4_descs.c).
> > 
> > Signed-off-by: Boon Khai Ng <boon.khai.ng@...era.com>
> > Reviewed-by: Matthew Gerlach <matthew.gerlach@...era.com>
> 
> This patch does IMHO too many things together, and should be split in
> several ones, i.e.:
> - just moving the code in a separate file
> - rename functions and simbols.
> - other random changes...
> 
> > -	ret = readl_poll_timeout(ioaddr + GMAC_VLAN_TAG, val,
> > -				 !(val & GMAC_VLAN_TAG_CTRL_OB),
> > -				 1000, 500000);
> > -	if (ret) {
> > -		netdev_err(dev, "Timeout accessing MAC_VLAN_Tag_Filter\n");
> > -		return -EBUSY;
> > -	}
> 
> > +	for (i = 0; i < timeout; i++) {
> > +		val = readl(ioaddr + VLAN_TAG);
> > +		if (!(val & VLAN_TAG_CTRL_OB))
> > +			return 0;
> > +		udelay(1);
> > +	}
> > +
> > +	netdev_err(dev, "Timeout accessing MAC_VLAN_Tag_Filter\n");
> > +
> > +	return -EBUSY;
> 
> ... like the above on (which looks unnecessary?!?)

Also looks like a backward step, because we ask people to use the helper
macros where possible.

-- 
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