| Message ID | 20210830214859.403100-4-linus.walleij@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | RTL8366RB improvements | expand |
On Mon, Aug 30, 2021 at 11:48:57PM +0200, Linus Walleij wrote: > The RTL8366RB hardware supports disabling learning per-port > so let's make use of this feature. Rename some unfortunately > named registers in the process. > > Suggested-by: Vladimir Oltean <olteanv@gmail.com> > Cc: Alvin Šipraga <alsi@bang-olufsen.dk> > Cc: Mauri Sandberg <sandberg@mailfence.com> > Cc: DENG Qingfang <dqfext@gmail.com> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > ChangeLog v1->v2: > - New patch suggested by Vladimir. > --- > drivers/net/dsa/rtl8366rb.c | 47 +++++++++++++++++++++++++++++++++---- > 1 file changed, 42 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/dsa/rtl8366rb.c b/drivers/net/dsa/rtl8366rb.c > index 8b040440d2d4..2cadd3e57e8b 100644 > --- a/drivers/net/dsa/rtl8366rb.c > +++ b/drivers/net/dsa/rtl8366rb.c > @@ -14,6 +14,7 @@ > > #include <linux/bitops.h> > #include <linux/etherdevice.h> > +#include <linux/if_bridge.h> > #include <linux/interrupt.h> > #include <linux/irqdomain.h> > #include <linux/irqchip/chained_irq.h> > @@ -42,9 +43,12 @@ > /* Port Enable Control register */ > #define RTL8366RB_PECR 0x0001 > > -/* Switch Security Control registers */ > -#define RTL8366RB_SSCR0 0x0002 > -#define RTL8366RB_SSCR1 0x0003 > +/* Switch per-port learning disablement register */ > +#define RTL8366RB_PORT_LEARNDIS_CTRL 0x0002 > + > +/* Security control, actually aging register */ > +#define RTL8366RB_SECURITY_CTRL 0x0003 > + > #define RTL8366RB_SSCR2 0x0004 > #define RTL8366RB_SSCR2_DROP_UNKNOWN_DA BIT(0) > > @@ -912,12 +916,12 @@ static int rtl8366rb_setup(struct dsa_switch *ds) > rb->max_mtu[i] = 1532; > > /* Enable learning for all ports */ > - ret = regmap_write(smi->map, RTL8366RB_SSCR0, 0); > + ret = regmap_write(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, 0); So the expected behavior for standalone ports would be to _disable_ learning. In rtl8366rb_setup, they are standalone. > if (ret) > return ret; > > /* Enable auto ageing for all ports */ > - ret = regmap_write(smi->map, RTL8366RB_SSCR1, 0); > + ret = regmap_write(smi->map, RTL8366RB_SECURITY_CTRL, 0); > if (ret) > return ret; > > @@ -1148,6 +1152,37 @@ rtl8366rb_port_disable(struct dsa_switch *ds, int port) > rb8366rb_set_port_led(smi, port, false); > } > > +static int > +rtl8366rb_port_pre_bridge_flags(struct dsa_switch *ds, int port, > + struct switchdev_brport_flags flags, > + struct netlink_ext_ack *extack) > +{ > + /* We support enabling/disabling learning */ > + if (flags.mask & ~(BR_LEARNING)) > + return -EINVAL; > + > + return 0; > +} > + > +static int > +rtl8366rb_port_bridge_flags(struct dsa_switch *ds, int port, > + struct switchdev_brport_flags flags, > + struct netlink_ext_ack *extack) > +{ > + struct realtek_smi *smi = ds->priv; > + int ret; > + > + if (flags.mask & BR_LEARNING) { > + ret = regmap_update_bits(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, > + BIT(port), > + (flags.val & BR_LEARNING) ? 0 : BIT(port)); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > static int > rtl8366rb_port_bridge_join(struct dsa_switch *ds, int port, > struct net_device *bridge) > @@ -1600,6 +1635,8 @@ static const struct dsa_switch_ops rtl8366rb_switch_ops = { > .port_vlan_del = rtl8366_vlan_del, > .port_enable = rtl8366rb_port_enable, > .port_disable = rtl8366rb_port_disable, > + .port_pre_bridge_flags = rtl8366rb_port_pre_bridge_flags, > + .port_bridge_flags = rtl8366rb_port_bridge_flags, > .port_change_mtu = rtl8366rb_change_mtu, > .port_max_mtu = rtl8366rb_max_mtu, > }; > -- > 2.31.1 >
On Tue, Aug 31, 2021 at 12:40 AM Vladimir Oltean <olteanv@gmail.com> wrote: > > /* Enable learning for all ports */ > > - ret = regmap_write(smi->map, RTL8366RB_SSCR0, 0); > > + ret = regmap_write(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, 0); > > So the expected behavior for standalone ports would be to _disable_ > learning. In rtl8366rb_setup, they are standalone. OK I altered the code such that I disable learning on all ports instead, the new callback can be used to enable it. What about the CPU port here? Sorry if it is a dumb question... I just disabled learning on all ports including the CPU port, but should I just leave learning on on the CPU port? Yours, Linus Walleij
On Tue, Sep 07, 2021 at 05:52:01PM +0200, Linus Walleij wrote: > On Tue, Aug 31, 2021 at 12:40 AM Vladimir Oltean <olteanv@gmail.com> wrote: > > > > /* Enable learning for all ports */ > > > - ret = regmap_write(smi->map, RTL8366RB_SSCR0, 0); > > > + ret = regmap_write(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, 0); > > > > So the expected behavior for standalone ports would be to _disable_ > > learning. In rtl8366rb_setup, they are standalone. > > OK I altered the code such that I disable learning on all ports instead, > the new callback can be used to enable it. > > What about the CPU port here? Sorry if it is a dumb question... > > I just disabled learning on all ports including the CPU port, but > should I just leave learning on on the CPU port? Not a dumb question. DSA does not change the learning state of the CPU port and lets drivers choose among two solutions: (a) enable hardware address learning manually on it. This was the traditional approach, and the exact meaning of what this actually does will vary from one switch vendor to another, so you need to know what you get and if it complies with the network stack's expectations. At one end, you have ASICs where despite this setting, the {MAC SA, VLAN ID} will not be learned for packets injected towards a precise destination port specified in the DSA tag (so-called "control packets"). These ASICs would only learn the {MAC SA, VLAN ID} from packets sent from the CPU that are not injected precisely into a port, but forwarded freely according to the FDB (in the case of your Realtek tagging protocol, think of it as an all-zeroes destination port mask). These are so-called "data plane packets", and DSA has traditionally not had any means for building/sending one, hence the complete lack of address learning for this type of switches, practically. On the other end you will have switches which will learn the {MAC SA, VLAN ID} from both control and data packets, with no way of controlling which one gets learned and which one doesn't. This will further cause problems when you consider that some packets might need to be partially forwarded in software between switch ports that are members of a hardware bridge. In general, address learning must be recognized as a bridge layer function, and only packets pertaining to the data plane of a bridge must be subject to learning. Ergo: if you inject a packet into a standalone port, its MAC SA should not be learned (for reasons that have real life implications, but are a bit beside the point to detail here). There might also exist in-between hardware implementations, where there might be a global learning setting for the CPU port, with an override per packet (a bit in the DSA tag). (b) implement .port_fdb_add and .port_fdb_del and then set ds->assisted_learning_on_cpu_port = true. This was created exactly for the category of switches that won't learn from CPU-injected traffic even when asked to do so, but has since been extended to cover use cases even for switches where that is a possibility. For example, in a setup with multiple CPU ports (and this includes obscure setups where every switch has a single CPU port, but is part of a multi-chip topology), hardware address learning on any individual CPU port does not make sense, because that learned address would keep bouncing back and forth between one CPU port and the other, when it really should have stayed fixed on both. The way this option works is that it tells DSA to listen for switchdev events emitted by the bridge for FDB entries that were learned by the software path and point towards the general direction of the bridge (towards the bridge itself, or towards a non-DSA interface in the same bridge as a DSA port, like a Wi-Fi AP). These software FDB entries will then be installed through .port_fdb_add as static FDB entries on the CPU port(s), and removed when they are no longer needed. Drivers which support multiple CPU ports should then program these FDB entries to hardware in a way in which installing the entry towards CPU port B will not override a pre-existing FDB entry that was pointing towards CPU port A, but instead just append to the destination port mask of any pre-existing FDB entry. This is also the pattern used when programming multicast (MDB) entries to hardware. This solution also addresses the observation that packets injected towards standalone ports should not result in the {MAC SA, VLAN ID} getting learned, due to a combination of two factors: - When you set ds->assisted_learning_on_cpu_port = true, you must disable hardware learning on the CPU port(s) - Since the only FDB entries installed on the CPU port are ones originating from switchdev events emitted by a bridge, learning is limited to the bridging layer It is understandable if you do not want to opt into ds->assisted_learning_on_cpu_port, and if the way in which your DSA tagging protocol injects packets into the hardware will always remain as "control packets", this might not even show up any problem. Typically, "control packets" will be sent to the destination port mask from the DSA tag with no questions asked. That is to say, if you want to xmit a packet with a given {MAC DA, VLAN ID} towards port 0, but the same {MAC DA, VLAN ID} was already learned on the CPU port, the switch will be happy to send it towards port 0 precisely because it's a "control packet" and it will not look up the FDB for it. With "data packets" it's an entirely different story, the FDB will be looked up, and the switch will say "hey, I received a packet with this MAC DA from the CPU port, but my FDB says the destination is the CPU port. I am told to not reflect packets back from where they came from, so just drop it". If you are sure that neither you nor anyone else will ever implement support for data plane packets (bridge tx_fwd_offload) for this hardware, then statically enabling hardware learning on the CPU port might be enough if it actually works. There is a third option where you can still learn the {MAC SA, VLAN ID} in-band from bridging layer packets (and not from packets sent to standalone ports), without the overhead of extra SPI/MDIO/I2C transactions that the assisted learning feature requires. This third option is available if you can tell the switch to learn on a per-packet basis, and then to implement the tx_fwd_offload bridge feature. The idea is to tell the hardware, through the DSA tag on xmit, to only learn the MAC SA from packets which are sent on behalf of a bridge (these will have skb->offload_fwd_mark == true). So in the end, you have quite a bit of choice. First of all I would start by figuring out what the hardware is capable of doing. Enable the hardware learning bit on the CPU port, then build this setup: 192.168.100.3 br0 / \ / \ / \ swp0 swp1 | | Station A Station B 192.168.100.1 192.168.100.2 And ping br0 from Station A, attached to the swp0 of your board. Then tcpdump on Station B, to see all packets. If you see the ICMP requests sent by Station A towards br0, it means that the switch has not learned the MAC SA from br0's ICMP replies, and it basically doesn't know where the MAC address of br0 is. So it will always flood the packets targeting br0, towards all ports in br0's forwarding domain. "All ports" includes swp1 in this case, the curious neighbor. With address learning functioning properly on the CPU port, you will only see an initial pair of packets being flooded, that being during a time when the switch does not know what the intended destination is, because it has not seen that MAC DA in the MAC SA field of any prior packets on any ports.
diff --git a/drivers/net/dsa/rtl8366rb.c b/drivers/net/dsa/rtl8366rb.c index 8b040440d2d4..2cadd3e57e8b 100644 --- a/drivers/net/dsa/rtl8366rb.c +++ b/drivers/net/dsa/rtl8366rb.c @@ -14,6 +14,7 @@ #include <linux/bitops.h> #include <linux/etherdevice.h> +#include <linux/if_bridge.h> #include <linux/interrupt.h> #include <linux/irqdomain.h> #include <linux/irqchip/chained_irq.h> @@ -42,9 +43,12 @@ /* Port Enable Control register */ #define RTL8366RB_PECR 0x0001 -/* Switch Security Control registers */ -#define RTL8366RB_SSCR0 0x0002 -#define RTL8366RB_SSCR1 0x0003 +/* Switch per-port learning disablement register */ +#define RTL8366RB_PORT_LEARNDIS_CTRL 0x0002 + +/* Security control, actually aging register */ +#define RTL8366RB_SECURITY_CTRL 0x0003 + #define RTL8366RB_SSCR2 0x0004 #define RTL8366RB_SSCR2_DROP_UNKNOWN_DA BIT(0) @@ -912,12 +916,12 @@ static int rtl8366rb_setup(struct dsa_switch *ds) rb->max_mtu[i] = 1532; /* Enable learning for all ports */ - ret = regmap_write(smi->map, RTL8366RB_SSCR0, 0); + ret = regmap_write(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, 0); if (ret) return ret; /* Enable auto ageing for all ports */ - ret = regmap_write(smi->map, RTL8366RB_SSCR1, 0); + ret = regmap_write(smi->map, RTL8366RB_SECURITY_CTRL, 0); if (ret) return ret; @@ -1148,6 +1152,37 @@ rtl8366rb_port_disable(struct dsa_switch *ds, int port) rb8366rb_set_port_led(smi, port, false); } +static int +rtl8366rb_port_pre_bridge_flags(struct dsa_switch *ds, int port, + struct switchdev_brport_flags flags, + struct netlink_ext_ack *extack) +{ + /* We support enabling/disabling learning */ + if (flags.mask & ~(BR_LEARNING)) + return -EINVAL; + + return 0; +} + +static int +rtl8366rb_port_bridge_flags(struct dsa_switch *ds, int port, + struct switchdev_brport_flags flags, + struct netlink_ext_ack *extack) +{ + struct realtek_smi *smi = ds->priv; + int ret; + + if (flags.mask & BR_LEARNING) { + ret = regmap_update_bits(smi->map, RTL8366RB_PORT_LEARNDIS_CTRL, + BIT(port), + (flags.val & BR_LEARNING) ? 0 : BIT(port)); + if (ret) + return ret; + } + + return 0; +} + static int rtl8366rb_port_bridge_join(struct dsa_switch *ds, int port, struct net_device *bridge) @@ -1600,6 +1635,8 @@ static const struct dsa_switch_ops rtl8366rb_switch_ops = { .port_vlan_del = rtl8366_vlan_del, .port_enable = rtl8366rb_port_enable, .port_disable = rtl8366rb_port_disable, + .port_pre_bridge_flags = rtl8366rb_port_pre_bridge_flags, + .port_bridge_flags = rtl8366rb_port_bridge_flags, .port_change_mtu = rtl8366rb_change_mtu, .port_max_mtu = rtl8366rb_max_mtu, };
The RTL8366RB hardware supports disabling learning per-port so let's make use of this feature. Rename some unfortunately named registers in the process. Suggested-by: Vladimir Oltean <olteanv@gmail.com> Cc: Alvin Šipraga <alsi@bang-olufsen.dk> Cc: Mauri Sandberg <sandberg@mailfence.com> Cc: DENG Qingfang <dqfext@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- ChangeLog v1->v2: - New patch suggested by Vladimir. --- drivers/net/dsa/rtl8366rb.c | 47 +++++++++++++++++++++++++++++++++---- 1 file changed, 42 insertions(+), 5 deletions(-) -- 2.31.1