Subject: Re: [PATCH 1/2] net: emac: implement 802.1Q VLAN TX tagging support

From: Christian Lamparter <[email-masked]>
Date: Fri, 19 Oct 2018 17:56:31 +0200

On Wednesday, October 17, 2018 10:09:10 PM CEST Florian Fainelli wrote:
> On 10/17/2018 01:08 PM, Florian Fainelli wrote:
> > On 10/17/2018 12:53 PM, Christian Lamparter wrote:
> >> As per' APM82181 Embedded Processor User Manual 26.1 EMAC Features:
> >> VLAN:
> >>  - Support for VLAN tag ID in compliance with IEEE 802.3ac.
> >>  - VLAN tag insertion or replacement for transmit packets
> >>
> >> This patch completes the missing code for the VLAN tx tagging
> >> support, as the the EMAC_MR1_VLE was already enabled.
> >>
> >> Signed-off-by: Christian Lamparter <[email-masked]>
> >> ---
> >>  drivers/net/ethernet/ibm/emac/core.c | 32 ++++++++++++++++++++++++----
> >>  drivers/net/ethernet/ibm/emac/core.h |  6 +++++-
> >>  2 files changed, 33 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c
> >> index 760b2ad8e295..be560f9031f4 100644
> >> --- a/drivers/net/ethernet/ibm/emac/core.c
> >> +++ b/drivers/net/ethernet/ibm/emac/core.c
> >> @@ -37,6 +37,7 @@
> >>  #include <linux/ethtool.h>
> >>  #include <linux/mii.h>
> >>  #include <linux/bitops.h>
> >> +#include <linux/if_vlan.h>
> >>  #include <linux/workqueue.h>
> >>  #include <linux/of.h>
> >>  #include <linux/of_address.h>
> >> @@ -674,7 +675,7 @@ static int emac_configure(struct emac_instance *dev)
> >>  		 ndev->dev_addr[5]);
> >>  
> >>  	/* VLAN Tag Protocol ID */
> >> -	out_be32(&p->vtpid, 0x8100);
> >> +	out_be32(&p->vtpid, ETH_P_8021Q);
> >>  
> >>  	/* Receive mode register */
> >>  	r = emac_iff2rmr(ndev);
> >> @@ -1435,6 +1436,22 @@ static inline netdev_tx_t emac_xmit_finish(struct emac_instance *dev, int len)
> >>  	return NETDEV_TX_OK;
> >>  }
> >>  
> >> +static inline u16 emac_tx_vlan(struct emac_instance *dev, struct sk_buff *skb)
> >> +{
> >> +	/* Handle VLAN TPID and TCI insert if this is a VLAN skb */
> >> +	if (emac_has_feature(dev, EMAC_FTR_HAS_VLAN_CTAG_TX) &&
> >> +	    skb_vlan_tag_present(skb)) {
> >> +		struct emac_regs __iomem *p = dev->emacp;
> >> +
> >> +		/* update the VLAN TCI */
> >> +		out_be32(&p->vtci, (u32)skb_vlan_tag_get(skb));
> > 
> > The only case where this is likely not going to be 0x8100/ETH_P_8021Q is
> > if you do 802.1ad (QinQ) and you decided to somehow offload the S-Tag
> > instead of the C-Tag.
> 
> Sorry, looks like I mixed up TCI and TPID here, this looks obviously
> correct ;)

Ok, I wasn't really sure what to write anyway ;).

The hardware documentation mentions that:
"Support for VLAN tag ID in compliance with IEEE Draft 802.3ac/D1.0 standard".
It's too old for offloading any fancy QinQ stuff :(.