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Date: Fri, 1 Dec 2023 02:49:40 +0000
From: Jianheng Zhang <Jianheng.Zhang@...opsys.com>
To: Paolo Abeni <pabeni@...hat.com>, Serge Semin <fancer.lancer@...il.com>
CC: 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>,
        "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


> -----Original Message-----
> From: Paolo Abeni <pabeni@...hat.com>
> Sent: Thursday, November 30, 2023 10:14 PM
> To: Serge Semin <fancer.lancer@...il.com>
> Cc: Jianheng Zhang <jianheng@...opsys.com>; Alexandre Torgue <alexandre.torgue@...s.st.com>; Jose
> Abreu <joabreu@...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>; 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
> <lijames@...opsys.com>; Martin McKenny <mmckenny@...opsys.com>
> Subject: Re: [PATCH v3] net: stmmac: fix FPE events losing
> 
> On Thu, 2023-11-30 at 15:09 +0100, Paolo Abeni wrote:
> > On Thu, 2023-11-30 at 16:09 +0300, Serge Semin wrote:
> > > Hi Paolo
> > >
> > > On Thu, Nov 30, 2023 at 10:55:34AM +0100, Paolo Abeni wrote:
> > > > 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?
> > >
> > > The SRSP and SVER are self-cleared flags with no effect on zero
> > > writing. Their responsibility is to emit the Respond and Verify
> > > mPackets respectively. As soon as the packets are sent, the flags will
> > > be reset by hardware automatically. So no, they aren't a part of the
> > > status bits.
> > >
> > > Note since 'value' now isn't read from the MAC_FPE_CTRL_STS register,
> > > there is no point in clearing up these flags in the local variable
> > > because 'value' has now them cleared by default.
> > >
> > > Not sure whether a comment about that is required, since the described
> > > behavior is well documented in the Synopsys HW-manual.

Thanks for Serge’s explanation.
> >
> > Thanks for the explanation, it clarifies the things to me. I agree
> > there is no need for a patch change.
> 
> I'm sorry, I have to take back the last sentence: the submitter and SoB
> email address still don't match. @Jianheng: please fix it for good at
> the next iteration.

OH, sorry~ I mixed up my internet email address with the internal one. I will fix it and resend the patch. 

Best Regards, 
Jianheng
> 
> Cheers,
> 
> Paolo

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