Re: [PATCH net] net: bcmgenet: if UMAC was suspended in SW_RESET, restore it to SW_RESET

[Nicolai Buchwitz <nb@tipi-net.de>]

Hi Justin

On 29.9.2026 21:22, Justin Chen wrote:
> When the revised suspend/resume sequence was introduced this led to an 
> edge
> case where the TX is left disabled in the following sequence.
> 
> 1. phy link is down, so UMAC is held in reset and then network 
> interface
>    is WoL enabled
> 2. Enter suspend, bcmgenet_wol_power_down_cfg() enables UMAC_RX since 
> MAC
>    is in SW_RESET
> 4. Enter resume, UMAC_RX is left enabled. Since we only enable UMAC_TX
>    and UMAC_RX in SW_RESET. The UMAC_TX is never enabled again on link 
> up.
> 
> Fixes: 254f3239dd07 ("net: bcmgenet: revise suspend/resume")
> Fixes: 88f6c8bf1aae ("net: bcmgenet: keep MAC in reset until PHY is 
> up")

AFAIU before 254f3239dd07 resume always went through init_umac(), so 
older
kernels shouldn't be affected. If we drop the tag for, it would save 
some
backports to the older LTS kernels.

> Signed-off-by: Justin Chen <justin.chen@broadcom.com>
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c 
> b/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c
> index 96d5d4f7f51f..984432952963 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c
> @@ -253,6 +253,17 @@ int bcmgenet_wol_power_up_cfg(struct bcmgenet_priv 
> *priv,
>  	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
>  	reg &= ~CMD_CRC_FWD;
>  	bcmgenet_umac_writel(priv, reg, UMAC_CMD);
> +
> +	/*
> +	 * Mirror wol_power_down_cfg(). If only UMAC_RX
> +	 * is enabled, then we must place the UMAC back
> +	 * into SW_RESET.
> +	 */
> +	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
> +	if ((reg & CMD_RX_EN) && !(reg & CMD_TX_EN)) {
> +		reg |= CMD_SW_RESET;
> +		bcmgenet_umac_writel(priv, reg, UMAC_CMD);
> +	}
>  	spin_unlock_bh(&priv->reg_lock);
> 
>  	/* Resume link status tracking */

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>

Thanks,
Nicolai