linux-kernel - Re: [PATCH net v2] net: stmmac: Set MAC's flow control register to reflect current settings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y30XoUHXscGSMHaL@shell.armlinux.org.uk>
Date:   Tue, 22 Nov 2022 18:40:33 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     "Goh, Wei Sheng" <wei.sheng.goh@...el.com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Voon Wei Feng <weifeng.voon@...el.com>,
        Tan Tee Min <tee.min.tan@...el.com>,
        Ahmad Tarmizi Noor Azura <noor.azura.ahmad.tarmizi@...el.com>,
        Looi Hong Aun <hong.aun.looi@...el.com>
Subject: Re: [PATCH net v2] net: stmmac: Set MAC's flow control register to
 reflect current settings

On Tue, Nov 22, 2022 at 02:39:35PM +0800, Goh, Wei Sheng wrote:
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> index c25bfecb4a2d..369db308b1dd 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> @@ -748,6 +748,9 @@ static void dwmac4_flow_ctrl(struct mac_device_info *hw, unsigned int duplex,
>  	if (fc & FLOW_RX) {
>  		pr_debug("\tReceive Flow-Control ON\n");
>  		flow |= GMAC_RX_FLOW_CTRL_RFE;
> +	} else {
> +		pr_debug("\tReceive Flow-Control OFF\n");
> +		flow &= ~GMAC_RX_FLOW_CTRL_RFE;
>  	}
>  	writel(flow, ioaddr + GMAC_RX_FLOW_CTRL);

This doesn't look correct to me. The function starts off:

        unsigned int flow = 0;

flow is not written to before the context above. So, the code you've
added effectively does:

	flow = 0 & ~GMAC_RX_FLOW_CTRL_RFE;

which is still zero. So, I don't think this hunk is meaningful apart
from adding the pr_debug().

> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 8273e6a175c8..ab7f48f32f5b 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1061,8 +1061,16 @@ static void stmmac_mac_link_up(struct phylink_config *config,
>  		ctrl |= priv->hw->link.duplex;
>  
>  	/* Flow Control operation */
> -	if (tx_pause && rx_pause)
> -		stmmac_mac_flow_ctrl(priv, duplex);
> +	if (rx_pause && tx_pause)
> +		priv->flow_ctrl = FLOW_AUTO;
> +	else if (rx_pause && !tx_pause)
> +		priv->flow_ctrl = FLOW_RX;
> +	else if (!rx_pause && tx_pause)
> +		priv->flow_ctrl = FLOW_TX;
> +	else
> +		priv->flow_ctrl = FLOW_OFF;
> +
> +	stmmac_mac_flow_ctrl(priv, duplex);
>  
>  	if (ctrl != old_ctrl)
>  		writel(ctrl, priv->ioaddr + MAC_CTRL_REG);

This looks like the true fix for correctly setting the flow control
depending on the phylink link_up() (which will contain the resuts of
pause negotiation, rate adaption or overriden by ethtool - but only
when operating in full duplex mode.)

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!