Re: [PATCH net-next v1 1/1] net: dsa: microchip: ksz8: add MTU configuration support

From: Arun.Ramadoss
Date: Thu Nov 03 2022 - 10:04:03 EST

On Thu, 2022-11-03 at 10:57 +0000, Arun Ramadoss - I17769 wrote:
> Hi Oleksij,
>
> On Thu, 2022-11-03 at 10:13 +0100, Oleksij Rempel wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you
> > know the content is safe
> >
> > 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.
> >
> > Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> > ---
> > drivers/net/dsa/microchip/ksz8.h | 2 +
> > drivers/net/dsa/microchip/ksz8795.c | 74
> > ++++++++++++++++++++++++-
> > drivers/net/dsa/microchip/ksz8795_reg.h | 9 +++
> > drivers/net/dsa/microchip/ksz_common.c | 2 +
> > 4 files changed, 85 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/dsa/microchip/ksz8.h
> > b/drivers/net/dsa/microchip/ksz8.h
> > index 8582b4b67d98..027b92f5fa73 100644
> > --- a/drivers/net/dsa/microchip/ksz8.h
> > +++ b/drivers/net/dsa/microchip/ksz8.h
> > @@ -57,5 +57,7 @@ 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);
> > +int ksz8_max_mtu(struct ksz_device *dev, int port);
> >
> > #endif
> > diff --git a/drivers/net/dsa/microchip/ksz8795.c
> > b/drivers/net/dsa/microchip/ksz8795.c
> > index bd3b133e7085..fd2539aabb2c 100644
> > --- a/drivers/net/dsa/microchip/ksz8795.c
> > +++ b/drivers/net/dsa/microchip/ksz8795.c
> > @@ -76,6 +76,78 @@ 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 <= KSZ8863_LEGAL_PACKET_SIZE)
> > + ctrl2 |= KSZ8863_LEGAL_PACKET_ENABLE;
> > + else if (max_frame > KSZ8863_NORMAL_PACKET_SIZE)
> > + ctrl2 |= KSZ8863_HUGE_PACKET_ENABLE;
> > +
> > + return regmap_update_bits(dev->regmap[0], REG_SW_CTRL_2,
> > + KSZ8863_LEGAL_PACKET_ENABLE
> > + | KSZ8863_HUGE_PACKET_ENABLE,
> > ctrl2);
> > +}
>
> Suggestion:
> regmap_update_bits, can you create a macro like ksz_rmw8 similar to
> what we have ksz_prmw8 in ksz_common.h. So that it can used across
> the
> ksz and lan937x switches.
>
> > +
> > +static int ksz8795_change_mtu(struct ksz_device *dev, int port,
> > int
> > max_frame)
> > +{
> > + u8 ctrl1 = 0, ctrl2 = 0;
> > + int ret;
> > +
> > + if (max_frame > KSZ8863_LEGAL_PACKET_SIZE)
> > + ctrl2 |= SW_LEGAL_PACKET_DISABLE;
> > + else if (max_frame > KSZ8863_NORMAL_PACKET_SIZE)
> > + ctrl1 |= SW_HUGE_PACKET;
> > +
> > + ret = regmap_update_bits(dev->regmap[0], REG_SW_CTRL_1,
> > + SW_HUGE_PACKET, ctrl1);
> > + if (ret)
> > + return ret;
> > +
> > + return regmap_update_bits(dev->regmap[0], 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);
>
> This port caching snippet is present in ksz9477_change_mtu function
> also. It can be moved to ksz_change_mtu and remove it in
> ksz9477_change_mtu.

I overlooked code. Caching port max frame is applicable only ksz9477
not for lan937x. In lan937x it has per port mtu settings where ksz has
switch wide mtu seeting.

>
> > +
> > + 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;
> > +}
> > +
> > +int ksz8_max_mtu(struct ksz_device *dev, int port)
> > +{
> > + 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;
> > + }
> > +
> > + return -EOPNOTSUPP;
> > +}
> > +
>
> Intially KSZ9477 had the max_mtu which I used for the LAN937x. Since
> there is no much thing to do in this function, why can't we move it
> ksz_common.c and add chip id for ksz9 and lan937x & remove
> ksz9477_max_mtu. It will reduce the max_mtu functioin pointer in
> ksz_dev_ops.
>
> >
> > diff --git a/drivers/net/dsa/microchip/ksz_common.c
> > b/drivers/net/dsa/microchip/ksz_common.c
> > index d612181b3226..40fd78951bf8 100644
> > --- a/drivers/net/dsa/microchip/ksz_common.c
> > +++ b/drivers/net/dsa/microchip/ksz_common.c
> > @@ -171,6 +171,8 @@ 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,
> > + .max_mtu = ksz8_max_mtu,
> > };
> >
> > static void ksz9477_phylink_mac_link_up(struct ksz_device *dev,
> > int
> > port,
> > -
> > 2.30.2
> >