linux-kernel - Re: [PATCH v3] net: stmmac: fix FPE events losing

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Message-ID: <1716792a3881338b1a416b1f4dd85a9437746ec2.camel@redhat.com>
Date:   Thu, 30 Nov 2023 10:55:34 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jianheng Zhang <Jianheng.Zhang@...opsys.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Simon Horman <horms@...nel.org>,
        Andrew Halaney <ahalaney@...hat.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Shenwei Wang <shenwei.wang@....com>,
        Johannes Zink <j.zink@...gutronix.de>,
        "Russell King (Oracle" <rmk+kernel@...linux.org.uk>,
        Jochen Henneberg <jh@...neberg-systemdesign.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Tan Tee Min <tee.min.tan@...el.com>
Cc:     "open list:STMMAC ETHERNET DRIVER" <netdev@...r.kernel.org>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        James Li <James.Li1@...opsys.com>,
        Martin McKenny <Martin.McKenny@...opsys.com>
Subject: Re: [PATCH v3] net: stmmac: fix FPE events losing

On Tue, 2023-11-28 at 05:56 +0000, Jianheng Zhang wrote:
> The status bits of register MAC_FPE_CTRL_STS are clear on read. Using
> 32-bit read for MAC_FPE_CTRL_STS in dwmac5_fpe_configure() and
> dwmac5_fpe_send_mpacket() clear the status bits. Then the stmmac interrupt
> handler missing FPE event status and leads to FPE handshaking failure and
> retries.
> To avoid clear status bits of MAC_FPE_CTRL_STS in dwmac5_fpe_configure()
> and dwmac5_fpe_send_mpacket(), add fpe_csr to stmmac_fpe_cfg structure to
> cache the control bits of MAC_FPE_CTRL_STS and to avoid reading
> MAC_FPE_CTRL_STS in those methods.
> 
> Fixes: 5a5586112b92 ("net: stmmac: support FPE link partner hand-shaking procedure")
> Reviewed-by: Serge Semin <fancer.lancer@...il.com>
> Signed-off-by: Jianheng Zhang <jianheng@...opsys.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac5.c       | 45 +++++++++-------------
>  drivers/net/ethernet/stmicro/stmmac/dwmac5.h       |  4 +-
>  .../net/ethernet/stmicro/stmmac/dwxgmac2_core.c    |  3 +-
>  drivers/net/ethernet/stmicro/stmmac/hwif.h         |  4 +-
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c  |  8 +++-
>  drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c    |  1 +
>  include/linux/stmmac.h                             |  1 +
>  7 files changed, 36 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> index e95d35f..8fd1675 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> @@ -710,28 +710,22 @@ void dwmac5_est_irq_status(void __iomem *ioaddr, struct net_device *dev,
>  	}
>  }
>  
> -void dwmac5_fpe_configure(void __iomem *ioaddr, u32 num_txq, u32 num_rxq,
> +void dwmac5_fpe_configure(void __iomem *ioaddr, struct stmmac_fpe_cfg *cfg,
> +			  u32 num_txq, u32 num_rxq,
>  			  bool enable)
>  {
>  	u32 value;
>  
> -	if (!enable) {
> -		value = readl(ioaddr + MAC_FPE_CTRL_STS);
> -
> -		value &= ~EFPE;
> -
> -		writel(value, ioaddr + MAC_FPE_CTRL_STS);
> -		return;
> +	if (enable) {
> +		cfg->fpe_csr = EFPE;
> +		value = readl(ioaddr + GMAC_RXQ_CTRL1);
> +		value &= ~GMAC_RXQCTRL_FPRQ;
> +		value |= (num_rxq - 1) << GMAC_RXQCTRL_FPRQ_SHIFT;
> +		writel(value, ioaddr + GMAC_RXQ_CTRL1);
> +	} else {
> +		cfg->fpe_csr = 0;
>  	}
> -
> -	value = readl(ioaddr + GMAC_RXQ_CTRL1);
> -	value &= ~GMAC_RXQCTRL_FPRQ;
> -	value |= (num_rxq - 1) << GMAC_RXQCTRL_FPRQ_SHIFT;
> -	writel(value, ioaddr + GMAC_RXQ_CTRL1);
> -
> -	value = readl(ioaddr + MAC_FPE_CTRL_STS);
> -	value |= EFPE;
> -	writel(value, ioaddr + MAC_FPE_CTRL_STS);
> +	writel(cfg->fpe_csr, ioaddr + MAC_FPE_CTRL_STS);
>  }
>  
>  int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
> @@ -741,6 +735,9 @@ int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
>  
>  	status = FPE_EVENT_UNKNOWN;
>  
> +	/* Reads from the MAC_FPE_CTRL_STS register should only be performed
> +	 * here, since the status flags of MAC_FPE_CTRL_STS are "clear on read"
> +	 */
>  	value = readl(ioaddr + MAC_FPE_CTRL_STS);
>  
>  	if (value & TRSP) {
> @@ -766,19 +763,15 @@ int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
>  	return status;
>  }
>  
> -void dwmac5_fpe_send_mpacket(void __iomem *ioaddr, enum stmmac_mpacket_type type)
> +void dwmac5_fpe_send_mpacket(void __iomem *ioaddr, struct stmmac_fpe_cfg *cfg,
> +			     enum stmmac_mpacket_type type)
>  {
> -	u32 value;
> +	u32 value = cfg->fpe_csr;
>  
> -	value = readl(ioaddr + MAC_FPE_CTRL_STS);
> -
> -	if (type == MPACKET_VERIFY) {
> -		value &= ~SRSP;
> +	if (type == MPACKET_VERIFY)
>  		value |= SVER;
> -	} else {
> -		value &= ~SVER;
> +	else if (type == MPACKET_RESPONSE)
>  		value |= SRSP;
> -	}
>  
>  	writel(value, ioaddr + MAC_FPE_CTRL_STS);
>  }

It's unclear to me why it's not necessary to preserve the SVER/SRSP
bits across MAC_FPE_CTRL_STS writes. I guess they are not part of the
status bits? perhaps an explicit comment somewhere will help?

Thanks

Paolo