Subject: Re: [PATCH net-next v2 2/2] net: dsa: realtek: rtl8365mb: add support for rtl8_4t

From: Alvin Šipraga <[email-masked]>
Date: Fri, 18 Feb 2022 12:26:28 +0000

Luiz Angelo Daros de Luca <[email-masked]> writes:

> The trailing tag is also supported by this family. The default is still
> rtl8_4 but now the switch supports changing the tag to rtl8_4t.
>
> Signed-off-by: Luiz Angelo Daros de Luca <[email-masked]>
> ---
>  drivers/net/dsa/realtek/rtl8365mb.c | 78 ++++++++++++++++++++++++-----
>  1 file changed, 66 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/dsa/realtek/rtl8365mb.c b/drivers/net/dsa/realtek/rtl8365mb.c
> index 2ed592147c20..043cac34e906 100644
> --- a/drivers/net/dsa/realtek/rtl8365mb.c
> +++ b/drivers/net/dsa/realtek/rtl8365mb.c
> @@ -524,9 +524,7 @@ enum rtl8365mb_cpu_rxlen {
>   * @mask: port mask of ports that parse should parse CPU tags
>   * @trap_port: forward trapped frames to this port
>   * @insert: CPU tag insertion mode in switch->CPU frames
> - * @position: position of CPU tag in frame
>   * @rx_length: minimum CPU RX length
> - * @format: CPU tag format
>   *
>   * Represents the CPU tagging and CPU port configuration of the switch. These
>   * settings are configurable at runtime.
> @@ -536,9 +534,7 @@ struct rtl8365mb_cpu {
>  	u32 mask;
>  	u32 trap_port;
>  	enum rtl8365mb_cpu_insert insert;
> -	enum rtl8365mb_cpu_position position;
>  	enum rtl8365mb_cpu_rxlen rx_length;
> -	enum rtl8365mb_cpu_format format;

This struct is meant to represent the whole CPU config register. Rather
than pulling it out and adding tag_protocol to struct rtl8365mb, can you
instead do something like:

- keep these members of _cpu
- put back the cpu member of struct rtl8365mb (I don't know why it was removed...)
- in get_tag_protocol: return mb->cpu.position == AFTER_SA ? RTL8_4 : RTL8_4T;
- in change_tag_protocol: just update mb->cpu.position and call
  rtl8365mb_cpu_config again
- avoid the arcane call to rtl8365mb_change_tag_protocol in _setup
- avoid the need to do regmap_update_bits instead of a clean
  regmap_write in one place

The reason I'm saying this is because, in the original version of the
driver, CPU configuration was in a single place. Now it is scattered. I
would kindly ask that you try to respect the existing design because I
can already see that things are starting to get a bit messy.

If we subsequently want to configure other CPU parameters on the fly, it
will be as easy as updating the cpu struct and calling cpu_config
again. This register is also non-volatile so the state we keep will
always conform with the switch configuration.

Sorry if you find the feedback too opinionated - I don't mean anything
personally. But the original design was not by accident, so I would
appreciate if we can keep it that way unless there is a good reason to
change it.

>  };
>  
>  /**
> @@ -566,6 +562,7 @@ struct rtl8365mb_port {
>   * @chip_ver: chip silicon revision
>   * @port_mask: mask of all ports
>   * @learn_limit_max: maximum number of L2 addresses the chip can learn
> + * @tag_protocol: current switch CPU tag protocol
>   * @mib_lock: prevent concurrent reads of MIB counters
>   * @ports: per-port data
>   * @jam_table: chip-specific initialization jam table
> @@ -580,6 +577,7 @@ struct rtl8365mb {
>  	u32 chip_ver;
>  	u32 port_mask;
>  	u32 learn_limit_max;
> +	enum dsa_tag_protocol tag_protocol;
>  	struct mutex mib_lock;
>  	struct rtl8365mb_port ports[RTL8365MB_MAX_NUM_PORTS];
>  	const struct rtl8365mb_jam_tbl_entry *jam_table;
> @@ -770,7 +768,54 @@ static enum dsa_tag_protocol
>  rtl8365mb_get_tag_protocol(struct dsa_switch *ds, int port,
>  			   enum dsa_tag_protocol mp)
>  {
> -	return DSA_TAG_PROTO_RTL8_4;
> +	struct realtek_priv *priv = ds->priv;
> +	struct rtl8365mb *chip_data;

Please stick to the convention and call this struct rtl8365mb pointer mb.

> +
> +	chip_data = priv->chip_data;
> +
> +	return chip_data->tag_protocol;
> +}
> +
> +static int rtl8365mb_change_tag_protocol(struct dsa_switch *ds, int cpu,
> +					 enum dsa_tag_protocol proto)
> +{
> +	struct realtek_priv *priv = ds->priv;
> +	struct rtl8365mb *chip_data;

s/chip_data/mb/ per convention

> +	int tag_position;
> +	int tag_format;
> +	int ret;
> +
> +	switch (proto) {
> +	case DSA_TAG_PROTO_RTL8_4:
> +		tag_format = RTL8365MB_CPU_FORMAT_8BYTES;
> +		tag_position = RTL8365MB_CPU_POS_AFTER_SA;
> +		break;
> +	case DSA_TAG_PROTO_RTL8_4T:
> +		tag_format = RTL8365MB_CPU_FORMAT_8BYTES;
> +		tag_position = RTL8365MB_CPU_POS_BEFORE_CRC;
> +		break;
> +	/* The switch also supports a 4-byte format, similar to rtl4a but with
> +	 * the same 0x04 8-bit version and probably 8-bit port source/dest.
> +	 * There is no public doc about it. Not supported yet.
> +	 */
> +	default:
> +		return -EPROTONOSUPPORT;
> +	}
> +
> +	ret = regmap_update_bits(priv->map, RTL8365MB_CPU_CTRL_REG,
> +				 RTL8365MB_CPU_CTRL_TAG_POSITION_MASK |
> +				 RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK,
> +				 FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_POSITION_MASK,
> +					    tag_position) |
> +				 FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK,
> +					    tag_format));
> +	if (ret)
> +		return ret;
> +
> +	chip_data = priv->chip_data;

nit: I would put this assignment up top like in the rest of the driver,
respecting reverse-christmass-tree order. It's nice to stick to the
existing style.

> +	chip_data->tag_protocol = proto;
> +
> +	return 0;
>  }
>  
>  static int rtl8365mb_ext_config_rgmii(struct realtek_priv *priv, int port,
> @@ -1739,13 +1784,18 @@ static int rtl8365mb_cpu_config(struct realtek_priv *priv, const struct rtl8365m
>  
>  	val = FIELD_PREP(RTL8365MB_CPU_CTRL_EN_MASK, cpu->enable ? 1 : 0) |
>  	      FIELD_PREP(RTL8365MB_CPU_CTRL_INSERTMODE_MASK, cpu->insert) |
> -	      FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_POSITION_MASK, cpu->position) |
>  	      FIELD_PREP(RTL8365MB_CPU_CTRL_RXBYTECOUNT_MASK, cpu->rx_length) |
> -	      FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK, cpu->format) |
>  	      FIELD_PREP(RTL8365MB_CPU_CTRL_TRAP_PORT_MASK, cpu->trap_port & 0x7) |
>  	      FIELD_PREP(RTL8365MB_CPU_CTRL_TRAP_PORT_EXT_MASK,
>  			 cpu->trap_port >> 3 & 0x1);
> -	ret = regmap_write(priv->map, RTL8365MB_CPU_CTRL_REG, val);
> +
> +	ret = regmap_update_bits(priv->map, RTL8365MB_CPU_CTRL_REG,
> +				 RTL8365MB_CPU_CTRL_EN_MASK |
> +				 RTL8365MB_CPU_CTRL_INSERTMODE_MASK |
> +				 RTL8365MB_CPU_CTRL_RXBYTECOUNT_MASK |
> +				 RTL8365MB_CPU_CTRL_TRAP_PORT_MASK |
> +				 RTL8365MB_CPU_CTRL_TRAP_PORT_EXT_MASK,
> +				 val);
>  	if (ret)
>  		return ret;
>  
> @@ -1827,6 +1877,11 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
>  		dev_info(priv->dev, "no interrupt support\n");
>  
>  	/* Configure CPU tagging */
> +	ret = rtl8365mb_change_tag_protocol(priv->ds, -1, DSA_TAG_PROTO_RTL8_4);
> +	if (ret) {
> +		dev_err(priv->dev, "failed to set default tag protocol: %d\n", ret);
> +		return ret;
> +	}
>  	cpu.trap_port = RTL8365MB_MAX_NUM_PORTS;
>  	dsa_switch_for_each_cpu_port(cpu_dp, priv->ds) {
>  		cpu.mask |= BIT(cpu_dp->index);
> @@ -1834,13 +1889,9 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
>  		if (cpu.trap_port == RTL8365MB_MAX_NUM_PORTS)
>  			cpu.trap_port = cpu_dp->index;
>  	}
> -
>  	cpu.enable = cpu.mask > 0;
>  	cpu.insert = RTL8365MB_CPU_INSERT_TO_ALL;
> -	cpu.position = RTL8365MB_CPU_POS_AFTER_SA;
>  	cpu.rx_length = RTL8365MB_CPU_RXLEN_64BYTES;
> -	cpu.format = RTL8365MB_CPU_FORMAT_8BYTES;

Like I said above, I think it would be nice to put this cpu struct back
in the rtl8365mb private data.

> -
>  	ret = rtl8365mb_cpu_config(priv, &cpu);
>  	if (ret)
>  		goto out_teardown_irq;
> @@ -1982,6 +2033,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
>  		mb->learn_limit_max = RTL8365MB_LEARN_LIMIT_MAX;
>  		mb->jam_table = rtl8365mb_init_jam_8365mb_vc;
>  		mb->jam_size = ARRAY_SIZE(rtl8365mb_init_jam_8365mb_vc);
> +		mb->tag_protocol = DSA_TAG_PROTO_RTL8_4;
>  
>  		break;
>  	default:
> @@ -1996,6 +2048,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
>  
>  static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
>  	.get_tag_protocol = rtl8365mb_get_tag_protocol,
> +	.change_tag_protocol = rtl8365mb_change_tag_protocol,
>  	.setup = rtl8365mb_setup,
>  	.teardown = rtl8365mb_teardown,
>  	.phylink_get_caps = rtl8365mb_phylink_get_caps,
> @@ -2014,6 +2067,7 @@ static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
>  
>  static const struct dsa_switch_ops rtl8365mb_switch_ops_mdio = {
>  	.get_tag_protocol = rtl8365mb_get_tag_protocol,
> +	.change_tag_protocol = rtl8365mb_change_tag_protocol,
>  	.setup = rtl8365mb_setup,
>  	.teardown = rtl8365mb_teardown,
>  	.phylink_get_caps = rtl8365mb_phylink_get_caps,