Re: [PATCH net-next v4 09/13] net: renesas: rswitch: update port HW init

[Jakub Kicinski <kuba@kernel.org>]

This is an AI-generated review of your patch. The human sending this
email has considered the AI review valid, or at least plausible.
---
net: renesas: rswitch: update port HW init

Certain Ethernet and cpu port settings need to be updated to prepare
for vlan support.

> diff --git a/drivers/net/ethernet/renesas/rswitch_main.c b/drivers/net/ethernet/renesas/rswitch_main.c
> index 90c44dcfd1691..d00af333fcce5 100644
> --- a/drivers/net/ethernet/renesas/rswitch_main.c
> +++ b/drivers/net/ethernet/renesas/rswitch_main.c
> @@ -737,8 +737,11 @@ static int rswitch_gwca_hw_init(struct rswitch_private *priv)
>  	if (err < 0)
>  		return err;
>  
> -	iowrite32(GWVCC_VEM_SC_TAG, priv->addr + GWVCC);
> -	iowrite32(0, priv->addr + GWTTFC);
> +	iowrite32(0, priv->addr + GWIRC);

Is it safe to completely remove the initialization of GWVCC here rather
than explicitly clearing it with iowrite32(0, priv->addr + GWVCC)?

If a bootloader, firmware, or a prior kernel (e.g., across a kexec warm
reboot) previously configured the switch to use Switch Control Tags,
this register might retain a stale VEM_SC_TAG value.

> +	iowrite32(FIELD_PREP(DQD, DES_RAM_DP), priv->addr + GWRDQDC0);
> +	/* Drop frames with unknown tags */
> +	iowrite32(UT, priv->addr + GWTTFC);
> +
>  	iowrite32(lower_32_bits(priv->gwca.linkfix_table_dma), priv->addr + GWDCBAC1);

[ ... ]

> @@ -1284,7 +1288,12 @@ static int rswitch_etha_hw_init(struct rswitch_etha *etha, const u8 *mac)
>  	if (err < 0)
>  		return err;
>  
> -	iowrite32(EAVCC_VEM_SC_TAG, etha->addr + EAVCC);
> +	iowrite32(0, etha->addr + EAIRC);

Similarly, should EAVCC be explicitly cleared to 0 here?

Other registers like EAIRC and GWIRC are being explicitly set to 0
in this patch, which suggests the driver cannot always rely on the hardware
reset state to zero out configurations.

If a stale value is retained in EAVCC, could it cause issues for subsequent
checks that might rely on reading EAVCC to determine if a default VLAN is
already set?

> +	iowrite32(FIELD_PREP(DQD, DES_RAM_DP), etha->addr + EATDQDC0);
> +
> +	/* Drop frames with unknown tags */
> +	iowrite32(UT, etha->addr + EARTFC);
> +
>  	rswitch_rmac_setting(etha, mac);