Subject: Re: [PATCH net-next v5 5/7] net: stmmac: Signal to PHY/PCS drivers to keep RX clock on

From: "Russell King (Oracle)" <[email-masked]>
Date: Mon, 4 Mar 2024 14:34:18 +0000

On Fri, Mar 01, 2024 at 04:35:02PM +0100, Romain Gantois wrote:
> There is a reocurring issue with stmmac controllers where the MAC fails to
> initialize its hardware if an RX clock signal isn't provided on the MAC/PHY
> link.
> 
> This causes issues when PHY or PCS devices either go into suspend while
> cutting the RX clock or do not bring the clock signal up early enough for
> the MAC to initialize successfully.
> 
> Set the mac_requires_rxc flag in the stmmac phylink config so that PHY/PCS
> drivers know to keep the RX clock up at all times.
> 
> Reported-by: Clark Wang <[email-masked]>
> Link: https://lore.kernel.org/all/[email-masked]/
> Reported-by: Clément Léger <[email-masked]>
> Link: https://lore.kernel.org/linux-arm-kernel/[email-masked]/
> Suggested-by: Russell King <[email-masked]>

This should be:
Co-developed-by: Russell King (Oracle) <[email-masked]>

> Signed-off-by: Romain Gantois <[email-masked]>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 79844dbe4258..2290f4808d7e 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1218,6 +1218,9 @@ static int stmmac_phy_setup(struct stmmac_priv *priv)
>  	priv->phylink_config.type = PHYLINK_NETDEV;
>  	priv->phylink_config.mac_managed_pm = true;
>  
> +	/* Stmmac always requires an RX clock for hardware initialization */
> +	priv->phylink_config.mac_requires_rxc = true;
> +
>  	mdio_bus_data = priv->plat->mdio_bus_data;
>  	if (mdio_bus_data)
>  		priv->phylink_config.ovr_an_inband =
> @@ -3408,6 +3411,10 @@ static int stmmac_hw_setup(struct net_device *dev, bool ptp_register)
>  	u32 chan;
>  	int ret;
>  
> +	/* Make sure RX clock is enabled */
> +	if (priv->hw->phylink_pcs)
> +		phylink_pcs_pre_init(priv->phylink, priv->hw->phylink_pcs);
> +
>  	/* DMA initialization and SW reset */
>  	ret = stmmac_init_dma_engine(priv);
>  	if (ret < 0) {
> 
> -- 
> 2.43.2
> 
> 

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