Re: [PATCH net-next 1/3] net: lan966x: Add function lan966x_mac_cpu_copy()

[Horatiu Vultur <horatiu.vultur@microchip.com>]

The 01/03/2022 14:27, Vladimir Oltean wrote:
> 
> On Mon, Jan 03, 2022 at 02:10:37PM +0100, Horatiu Vultur wrote:
> > Extend mac functionality with the function lan966x_mac_cpu_copy. This
> > function adds an entry in the MAC table where a frame is copy to the CPU
> 
> s/copy/copied/
> 
> > but also can be forward on the front ports.
> 
> s/forward/forwarded/
> 
> > This functionality is needed for mdb support. In case the CPU and some
> > of the front ports subscribe to an IP multicast address.
> >
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
> > ---
> >  .../ethernet/microchip/lan966x/lan966x_mac.c  | 27 ++++++++++++++++---
> >  .../ethernet/microchip/lan966x/lan966x_main.h |  5 ++++
> >  .../ethernet/microchip/lan966x/lan966x_regs.h |  6 +++++
> >  3 files changed, 34 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c b/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
> > index efadb8d326cc..ae3a7a10e0d6 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
> > @@ -68,16 +68,18 @@ static void lan966x_mac_select(struct lan966x *lan966x,
> >       lan_wr(mach, lan966x, ANA_MACHDATA);
> >  }
> >
> > -int lan966x_mac_learn(struct lan966x *lan966x, int port,
> > -                   const unsigned char mac[ETH_ALEN],
> > -                   unsigned int vid,
> > -                   enum macaccess_entry_type type)
> > +static int lan966x_mac_learn_impl(struct lan966x *lan966x, int port,
> > +                               bool cpu_copy,
> > +                               const unsigned char mac[ETH_ALEN],
> > +                               unsigned int vid,
> > +                               enum macaccess_entry_type type)
> 
> In the kernel, the __lan966x_mac_learn naming scheme seems to be more
> popular than _impl.
> 
> Also, may I suggest that the "int port" argument may be better named
> "int pgid"?

Yes, I will rename it and change the argument name.

> 
> >  {
> >       lan966x_mac_select(lan966x, mac, vid);
> >
> >       /* Issue a write command */
> >       lan_wr(ANA_MACACCESS_VALID_SET(1) |
> >              ANA_MACACCESS_CHANGE2SW_SET(0) |
> > +            ANA_MACACCESS_MAC_CPU_COPY_SET(cpu_copy) |
> >              ANA_MACACCESS_DEST_IDX_SET(port) |
> >              ANA_MACACCESS_ENTRYTYPE_SET(type) |
> >              ANA_MACACCESS_MAC_TABLE_CMD_SET(MACACCESS_CMD_LEARN),
> > @@ -86,6 +88,23 @@ int lan966x_mac_learn(struct lan966x *lan966x, int port,
> >       return lan966x_mac_wait_for_completion(lan966x);
> >  }
> >
> > +int lan966x_mac_cpu_copy(struct lan966x *lan966x, int port,
> > +                      bool cpu_copy,
> > +                      const unsigned char mac[ETH_ALEN],
> > +                      unsigned int vid,
> > +                      enum macaccess_entry_type type)
> 
> This doesn't seem to use the "port" argument from any of its call sites.
> It is always 0. What would it even mean?

When adding MAC table entries for IPv4/IPv6 then the port which is the
DEST_IDX needs to be 0. It should not point to a PGID entry because the
destination ports are encoded in the MAC address.

> 
> > +{
> > +     return lan966x_mac_learn_impl(lan966x, port, cpu_copy, mac, vid, type);
> > +}
> > +
> > +int lan966x_mac_learn(struct lan966x *lan966x, int port,
> > +                   const unsigned char mac[ETH_ALEN],
> > +                   unsigned int vid,
> > +                   enum macaccess_entry_type type)
> > +{
> > +     return lan966x_mac_learn_impl(lan966x, port, false, mac, vid, type);
> 
> If you call lan966x_mac_cpu_copy() on an address and then
> lan966x_mac_learn() on the same address but on an external port, how
> does that work (why doesn't the "false" here overwrite the cpu_copy in
> the previous command, breaking the copy-to-CPU feature)?

Then you will overwrite the cpu_copy so the frames will not reach the
CPU anymore.
But you should not do that. The function lan966x_mac_cpu_copy() should be
used for IPv4/IPv6 and lan966x_mac_learn() for the other types.

Maybe the function lan966x_mac_cpu_copy() is too generic. It should be
something like lan966x_mac_ipv4(), lan966x_mac_ipv6() and these functions
will call __lan966x_mac_learn with the correct parameters. Also I can
add a WARN_ON(...) inside lan966x_mac_learn not to be used with the
IPv4/IPv6 types.

> 
> > +}
> > +
> >  int lan966x_mac_forget(struct lan966x *lan966x,
> >                      const unsigned char mac[ETH_ALEN],
> >                      unsigned int vid,
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > index c399b1256edc..a7a2a3537036 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > @@ -157,6 +157,11 @@ int lan966x_port_pcs_set(struct lan966x_port *port,
> >                        struct lan966x_port_config *config);
> >  void lan966x_port_init(struct lan966x_port *port);
> >
> > +int lan966x_mac_cpu_copy(struct lan966x *lan966x, int port,
> > +                      bool cpu_copy,
> > +                      const unsigned char mac[ETH_ALEN],
> > +                      unsigned int vid,
> > +                      enum macaccess_entry_type type);
> >  int lan966x_mac_learn(struct lan966x *lan966x, int port,
> >                     const unsigned char mac[ETH_ALEN],
> >                     unsigned int vid,
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h b/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
> > index a13c469e139a..797560172aca 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
> > @@ -169,6 +169,12 @@ enum lan966x_target {
> >  #define ANA_MACACCESS_CHANGE2SW_GET(x)\
> >       FIELD_GET(ANA_MACACCESS_CHANGE2SW, x)
> >
> > +#define ANA_MACACCESS_MAC_CPU_COPY               BIT(16)
> > +#define ANA_MACACCESS_MAC_CPU_COPY_SET(x)\
> > +     FIELD_PREP(ANA_MACACCESS_MAC_CPU_COPY, x)
> > +#define ANA_MACACCESS_MAC_CPU_COPY_GET(x)\
> > +     FIELD_GET(ANA_MACACCESS_MAC_CPU_COPY, x)
> > +
> >  #define ANA_MACACCESS_VALID                      BIT(12)
> >  #define ANA_MACACCESS_VALID_SET(x)\
> >       FIELD_PREP(ANA_MACACCESS_VALID, x)
> > --
> > 2.33.0
> >

-- 
/Horatiu