Re: [PATCH net-next v3 3/3] net: dsa: microchip: ksz8: add MTU configuration support

[Arun.Ramadoss]

On Tue, 2022-11-08 at 06:43 +0100, Oleksij Rempel wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
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> 
> Make MTU configurable on KSZ87xx and KSZ88xx series of switches.
> 
> Before this patch, pre-configured behavior was different on different
> switch series, due to opposite meaning of the same bit:
> - KSZ87xx: Reg 4, Bit 1 - if 1, max frame size is 1532; if 0 - 1514
> - KSZ88xx: Reg 4, Bit 1 - if 1, max frame size is 1514; if 0 - 1532
> 
> Since the code was telling "... SW_LEGAL_PACKET_DISABLE, true)", I
> assume, the idea was to set max frame size to 1532.
> 
> With this patch, by setting MTU size 1500, both switch series will be
> configured to the 1532 frame limit.
> 
> This patch was tested on KSZ8873.

Acked-by: Arun Ramadoss <arun.ramadoss@xxxxxxxxxxxxx>

> 
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
>  drivers/net/dsa/microchip/ksz8.h        |  1 +
>  drivers/net/dsa/microchip/ksz8795.c     | 57
> ++++++++++++++++++++++++-
>  drivers/net/dsa/microchip/ksz8795_reg.h |  3 ++
>  drivers/net/dsa/microchip/ksz_common.c  |  7 +++
>  drivers/net/dsa/microchip/ksz_common.h  |  4 ++
>  5 files changed, 70 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz8.h
> b/drivers/net/dsa/microchip/ksz8.h
> index 8582b4b67d98..ea05abfbd51d 100644
> --- a/drivers/net/dsa/microchip/ksz8.h
> +++ b/drivers/net/dsa/microchip/ksz8.h
> @@ -57,5 +57,6 @@ int ksz8_reset_switch(struct ksz_device *dev);
>  int ksz8_switch_detect(struct ksz_device *dev);
>  int ksz8_switch_init(struct ksz_device *dev);
>  void ksz8_switch_exit(struct ksz_device *dev);
> +int ksz8_change_mtu(struct ksz_device *dev, int port, int mtu);
> 
>  #endif
> diff --git a/drivers/net/dsa/microchip/ksz8795.c
> b/drivers/net/dsa/microchip/ksz8795.c
> index bd3b133e7085..ac03625d427e 100644
> --- a/drivers/net/dsa/microchip/ksz8795.c
> +++ b/drivers/net/dsa/microchip/ksz8795.c
> @@ -76,6 +76,61 @@ int ksz8_reset_switch(struct ksz_device *dev)
>         return 0;
>  }
> 
> +static int ksz8863_change_mtu(struct ksz_device *dev, int port, int
> max_frame)
> +{
> +       u8 ctrl2 = 0;
> +
> +       if (max_frame <= KSZ8_LEGAL_PACKET_SIZE)
> +               ctrl2 |= KSZ8863_LEGAL_PACKET_ENABLE;
> +       else if (max_frame > KSZ8863_NORMAL_PACKET_SIZE)
> +               ctrl2 |= KSZ8863_HUGE_PACKET_ENABLE;
> +
> +       return ksz_rmw8(dev, REG_SW_CTRL_2,
> KSZ8863_LEGAL_PACKET_ENABLE
> +                       | KSZ8863_HUGE_PACKET_ENABLE, ctrl2);
> +}
> +
> +static int ksz8795_change_mtu(struct ksz_device *dev, int port, int
> max_frame)
> +{
> +       u8 ctrl1 = 0, ctrl2 = 0;
> +       int ret;
> +
> +       if (max_frame > KSZ8_LEGAL_PACKET_SIZE)
> +               ctrl2 |= SW_LEGAL_PACKET_DISABLE;
> +       else if (max_frame > KSZ8863_NORMAL_PACKET_SIZE)
> +               ctrl1 |= SW_HUGE_PACKET;
> +
> +       ret = ksz_rmw8(dev, REG_SW_CTRL_1, SW_HUGE_PACKET, ctrl1);
> +       if (ret)
> +               return ret;
> +
> +       return ksz_rmw8(dev, REG_SW_CTRL_2, SW_LEGAL_PACKET_DISABLE,
> ctrl2);
> +}
> +
> +int ksz8_change_mtu(struct ksz_device *dev, int port, int mtu)
> +{
> +       u16 frame_size, max_frame = 0;
> +       int i;
> +
> +       frame_size = mtu + VLAN_ETH_HLEN + ETH_FCS_LEN;
> +
> +       /* Cache the per-port MTU setting */
> +       dev->ports[port].max_frame = frame_size;
> +
> +       for (i = 0; i < dev->info->port_cnt; i++)
> +               max_frame = max(max_frame, dev->ports[i].max_frame);
> +
> +       switch (dev->chip_id) {
> +       case KSZ8795_CHIP_ID:
> +       case KSZ8794_CHIP_ID:
> +       case KSZ8765_CHIP_ID:
> +               return ksz8795_change_mtu(dev, port, max_frame);
> +       case KSZ8830_CHIP_ID:
> +               return ksz8863_change_mtu(dev, port, max_frame);
> +       }
> +
> +       return -EOPNOTSUPP;
> +}
> +
>  static void ksz8795_set_prio_queue(struct ksz_device *dev, int port,
> int queue)
>  {
>         u8 hi, lo;
> @@ -1233,8 +1288,6 @@ void ksz8_config_cpu_port(struct dsa_switch
> *ds)
>         masks = dev->info->masks;
>         regs = dev->info->regs;
> 
> -       /* Switch marks the maximum frame with extra byte as
> oversize. */
> -       ksz_cfg(dev, REG_SW_CTRL_2, SW_LEGAL_PACKET_DISABLE, true);
>         ksz_cfg(dev, regs[S_TAIL_TAG_CTRL],
> masks[SW_TAIL_TAG_ENABLE], true);
> 
>         p = &dev->ports[dev->cpu_port];
> diff --git a/drivers/net/dsa/microchip/ksz8795_reg.h
> b/drivers/net/dsa/microchip/ksz8795_reg.h
> index 77487d611824..7a57c6088f80 100644
> --- a/drivers/net/dsa/microchip/ksz8795_reg.h
> +++ b/drivers/net/dsa/microchip/ksz8795_reg.h
> @@ -48,6 +48,9 @@
>  #define NO_EXC_COLLISION_DROP          BIT(3)
>  #define SW_LEGAL_PACKET_DISABLE                BIT(1)
> 
> +#define KSZ8863_HUGE_PACKET_ENABLE     BIT(2)
> +#define KSZ8863_LEGAL_PACKET_ENABLE    BIT(1)
> +
>  #define REG_SW_CTRL_3                  0x05
>   #define WEIGHTED_FAIR_QUEUE_ENABLE    BIT(3)
> 
> diff --git a/drivers/net/dsa/microchip/ksz_common.c
> b/drivers/net/dsa/microchip/ksz_common.c
> index 486ad03d0acf..188c66145df7 100644
> --- a/drivers/net/dsa/microchip/ksz_common.c
> +++ b/drivers/net/dsa/microchip/ksz_common.c
> @@ -172,6 +172,7 @@ static const struct ksz_dev_ops ksz8_dev_ops = {
>         .reset = ksz8_reset_switch,
>         .init = ksz8_switch_init,
>         .exit = ksz8_switch_exit,
> +       .change_mtu = ksz8_change_mtu,
>  };
> 
>  static void ksz9477_phylink_mac_link_up(struct ksz_device *dev, int
> port,
> @@ -2473,6 +2474,12 @@ static int ksz_max_mtu(struct dsa_switch *ds,
> int port)
>         struct ksz_device *dev = ds->priv;
> 
>         switch (dev->chip_id) {
> +       case KSZ8795_CHIP_ID:
> +       case KSZ8794_CHIP_ID:
> +       case KSZ8765_CHIP_ID:
> +               return KSZ8795_HUGE_PACKET_SIZE - VLAN_ETH_HLEN -
> ETH_FCS_LEN;
> +       case KSZ8830_CHIP_ID:
> +               return KSZ8863_HUGE_PACKET_SIZE - VLAN_ETH_HLEN -
> ETH_FCS_LEN;
>         case KSZ8563_CHIP_ID:
>         case KSZ9477_CHIP_ID:
>         case KSZ9567_CHIP_ID:
> diff --git a/drivers/net/dsa/microchip/ksz_common.h
> b/drivers/net/dsa/microchip/ksz_common.h
> index 85ce6ec573ba..4a43a2cf7017 100644
> --- a/drivers/net/dsa/microchip/ksz_common.h
> +++ b/drivers/net/dsa/microchip/ksz_common.h
> @@ -589,6 +589,10 @@ static inline int is_lan937x(struct ksz_device
> *dev)
> 
>  #define PORT_SRC_PHY_INT               1
> 
> +#define KSZ8795_HUGE_PACKET_SIZE       2000
> +#define KSZ8863_HUGE_PACKET_SIZE       1916
> +#define KSZ8863_NORMAL_PACKET_SIZE     1536
> +#define KSZ8_LEGAL_PACKET_SIZE         1518
>  #define KSZ9477_MAX_FRAME_SIZE         9000
> 
>  /* Regmap tables generation */
> --
> 2.30.2
>