RE: [PATCH] net: stmmac: fix FPE events losing

From: Jianheng Zhang
Date: Thu Nov 23 2023 - 04:53:24 EST

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> From: Serge Semin <fancer.lancer@xxxxxxxxx>
> Sent: Wednesday, November 22, 2023 11:07 PM
> To: Jianheng Zhang <jianheng@xxxxxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>; Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>; Jose
> Abreu <joabreu@xxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet
> <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>;
> Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>; Tan Tee Min <tee.min.tan@xxxxxxxxx>; Ong Boon
> Leong <boon.leong.ong@xxxxxxxxx>; Voon Weifeng <weifeng.voon@xxxxxxxxx>; Mohammad Athari Bin
> Ismail <mohammad.athari.ismail@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; James Li <lijames@xxxxxxxxxxxx>; Martin McKenny
> <mmckenny@xxxxxxxxxxxx>
> Subject: Re: [PATCH] net: stmmac: fix FPE events losing
>
> On Wed, Nov 22, 2023 at 07:37:51AM +0000, Jianheng Zhang wrote:
> > > From: Serge Semin <fancer.lancer@xxxxxxxxx>
> > > Sent: Tuesday, November 21, 2023 8:09 PM
> > > To: Jianheng Zhang <jianheng@xxxxxxxxxxxx>
> > > Cc: Russell King <linux@xxxxxxxxxxxxxxx>; Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>; Jose
> > > Abreu <joabreu@xxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet
> > > <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>;
> > > Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>; Tan Tee Min <tee.min.tan@xxxxxxxxx>; Ong
> Boon
> > > Leong <boon.leong.ong@xxxxxxxxx>; Voon Weifeng <weifeng.voon@xxxxxxxxx>; Mohammad Athari
> Bin
> > > Ismail <mohammad.athari.ismail@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> > > linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > linux-kernel@xxxxxxxxxxxxxxx; James Li <lijames@xxxxxxxxxxxx>
> > > Subject: Re: [PATCH] net: stmmac: fix FPE events losing
> > >
> > > On Tue, Nov 21, 2023 at 09:31:31AM +0000, Jianheng Zhang wrote:
> > > > > From: Jianheng Zhang
> > > > > Sent: Thursday, November 16, 2023 12:01 AM
> > > > > To: Russell King <linux@xxxxxxxxxxxxxxx>; Serge Semin <fancer.lancer@xxxxxxxxx>
> > > > > Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>; Jose Abreu <joabreu@xxxxxxxxxxxx>;
> David
> > > S.
> > > > > Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski
> > > > > <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>; Maxime Coquelin
> > > > > <mcoquelin.stm32@xxxxxxxxx>; Tan Tee Min <tee.min.tan@xxxxxxxxx>; Ong Boon Leong
> > > > > <boon.leong.ong@xxxxxxxxx>; Voon Weifeng <weifeng.voon@xxxxxxxxx>; Mohammad Athari Bin
> > > Ismail
> > > > > <mohammad.athari.ismail@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> > > > > linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > > > linux-kernel@xxxxxxxxxxxxxxx
> > > > > Subject: RE: [PATCH] net: stmmac: fix FPE events losing
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Russell King <linux@xxxxxxxxxxxxxxx>
> > > > > > Sent: Wednesday, November 15, 2023 10:26 PM
> > > > > > To: Serge Semin <fancer.lancer@xxxxxxxxx>
> > > > > > Cc: Jianheng Zhang <jianheng@xxxxxxxxxxxx>; Alexandre Torgue
> > > <alexandre.torgue@xxxxxxxxxxx>;
> > > > > Jose
> > > > > > Abreu <joabreu@xxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet
> > > > > > <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni
> <pabeni@xxxxxxxxxx>;
> > > > > > Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>; Tan Tee Min <tee.min.tan@xxxxxxxxx>; Ong
> > > Boon
> > > > > > Leong <boon.leong.ong@xxxxxxxxx>; Voon Weifeng <weifeng.voon@xxxxxxxxx>; Mohammad
> > > Athari
> > > > > Bin
> > > > > > Ismail <mohammad.athari.ismail@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> > > > > > linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > > > > linux-kernel@xxxxxxxxxxxxxxx
> > > > > > Subject: Re: [PATCH] net: stmmac: fix FPE events losing
> > > > > >
> > > > > > On Tue, Nov 14, 2023 at 02:59:57PM +0300, Serge Semin wrote:
> > > > > > > On Tue, Nov 14, 2023 at 11:07:34AM +0000, Jianheng Zhang wrote:
> > > > > > > > The 32-bit access of register MAC_FPE_CTRL_STS may clear the FPE status
> > > > > > > > bits unexpectedly. Use 8-bit access for MAC_FPE_CTRL_STS control bits to
> > > > > > > > avoid unexpected access of MAC_FPE_CTRL_STS status bits that can reduce
> > > > > > > > the FPE handshake retries.
> > > > > > > >
> > > > > > > > The bit[19:17] of register MAC_FPE_CTRL_STS are status register bits.
> > > > > > > > Those bits are clear on read (or write of 1 when RCWE bit in
> > > > > > > > MAC_CSR_SW_Ctrl register is set). Using 32-bit access for
> > > > > > > > MAC_FPE_CTRL_STS control bits makes side effects that clear the status
> > > > > > > > bits. Then the stmmac interrupt handler missing FPE event status and
> > > > > > > > leads to FPE handshake failure and retries.
> > > > > > > >
> > > > > > > > The bit[7:0] of register MAC_FPE_CTRL_STS are control bits or reserved
> > > > > > > > that have no access side effects, so can use 8-bit access for
> > > > > > > > MAC_FPE_CTRL_STS control bits.
> > > > > > > >
> > > > > > > > Fixes: 5a5586112b92 ("net: stmmac: support FPE link partner hand-shaking procedure")
> > > > > > > > Signed-off-by: jianheng <jianheng@xxxxxxxxxxxx>
> > > > > > > > ---
> > > > > > > > drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 12 ++++++------
> > > > > > > > 1 file changed, 6 insertions(+), 6 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > > > b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > > > > > index e95d35f..7333995 100644
> > > > > > > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > > > > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > > > > > @@ -716,11 +716,11 @@ void dwmac5_fpe_configure(void __iomem *ioaddr, u32
> num_txq,
> > > u32
> > > > > > num_rxq,
> > > > > > > > u32 value;
> > > > > > > >
> > > > > > > > if (!enable) {
> > > > > > >
> > > > > > > > - value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > > > > > > > + value = readb(ioaddr + MAC_FPE_CTRL_STS);
> > > > > > >
> > > > > > > Note this may break the platforms which don't support non-32 MMIOs for
> > > > > > > some devices. None of the currently supported glue-drivers explicitly
> > > > > > > state they have such peculiarity, but at the same time the STMMAC-core
> > > > > > > driver at the present state uses the dword IO ops only. For instance
> > > > > > > the PCIe subsystem has the special accessors for such cases:
> > > > > > > pci_generic_config_read32()
> > > > > > > pci_generic_config_write32()
> > > > > > > which at the very least are utilized on the Tegra and Loongson
> > > > > > > platforms to access the host CSR spaces. These platforms are also
> > > > > > > equipped with the DW MACs. The problem might be irrelevant for all the
> > > > > > > currently supported DW MAC controllers implementations though, but
> > > > > > > still it worth to draw an attention to the problem possibility and in
> > > > > > > order to prevent it before ahead it would be better to just avoid
> > > > > > > using the byte-/word- IOs if it's possible.
> > > > > >
> > > > > > Yes, this exists for configuration accesses, and is damn annoying
> > > > > > because the read-modify-write of these can end up clearing PCI
> > > > > > status register bits that are W1C.
> > > > > >
> > > > > > I've never heard of that problem with MMIO though.
> > > > > >
> > > > > > --
> > > > > > RMK's Patch system:
> > > > > >
> > > > >
> > >
> https://urldefense.com/v3/__https://www.armlinux.org.uk/developer/patches/__;!!A4F2R9G_pg!ZnsQc
> > > > > >
> > > > >
> > >
> 7LKbdCiIj_nLBkt44MRSL8W8YD4WvMmPNkHFlDMrjrVqEVOVA1-P-9BVE3Oa5bC1ymKXLNV5C9mJ_rfFtLW
> > > > > > Fg$
> > > > > > FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
> > > > > Thanks for all your mention about the potential risks of using readb and suggestions, I'll consider a
> > > new
> > > > > solution and update the patch.
> > > > >
> > > > > Best Regards,
> > > > > Jianheng
> > > >
> > > > Thanks for Andrew's suggestion. I consider the solution of set
> > > > MAC_CSR_SW_Ctrl.RCWE carefully and found that the MAC_CSR_SW_Ctrl.RCWE
> > > > is efficient for many other interrupt status registers, and some are used
> > > > in current stmmac driver (LPI PMT MMC etc). Those registers work fine in
> > > > clear on read mode with current code. So, I think there is no need to
> > > > set MAC_CSR_SW_Ctrl.RCWE that will make a large impact to current
> > > > interrupt handler.
> > > >
> > > > I try adding a new member variable(staged_fpe_state) to stmmac_fpe_cfg
> > > > that is used to stage the MAC_FPE_CTRL_STS value read in
> > > > dwmac5_fpe_send_mpacket(). And in dwmac5_fpe_irq_status(), use this staged
> > > > value and current value of MAC_FPE_CTRL_STS to check FPE status. The
> > > > draft patch is below.
> > >
> > > Are the status flags in the MAC_FPE_CTRL_STS register cleared on
> > > _writes_? (I am asking because for some reason my DW QoS Eth v5.10a HW
> > > manual has the status MAC_FPE_CTRL_STS flags marked as R/W, which is
> > > weird access mode for the status flags.) If they turn to be _not_
> > > changeable on writes, then what about just converting the
> > > dwmac5_fpe_configure() and dwmac5_fpe_send_mpacket() methods to always
> > > writing to the MAC_FPE_CTRL_STS register, and if required preserve the
> > > shadow control MAC_FPE_CTRL_STS flags in the stmmac_fpe_cfg structure?
> > > AFAICS the only flag which needs to be preserved is EFPE - "enable
> > > FPE" flag.
> > >
> > > Such implementation (if it's possible) shall be free from the _status_
> > > flags race condition and won't require additional serializations. On
> > > the contrary your suggestion AFAICS causes unresolved race condition
> > > in here
> > >
> > > > + value = readl(ioaddr + MAC_FPE_CTRL_STS) | fpe_cfg->staged_fpe_state;
> > > > + fpe_cfg->staged_fpe_state = 0x0;
> > >
> > > and here
> > >
> > > > value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > > > + cfg->staged_fpe_state = value;
> > >
> > > Depending on the IRQ handling and the task scheduling timing you may
> > > end up with loosing the status flags anyway.
> > >
> > > * Note I am not concerning here the MAC_FPE_CTRL_STS control flags
> > > * race condition which AFAICS already exist in the current frame
> > > * preemption code. See the configs performed in the open/close/suspend
> > > * methods, in the link state change callbacks, in the worker task and
> > > * in the FPE status IRQ handler. Control flag accesses don't look
> > > * coherent there.
> > >
> > > -Serge(y)
> > >
> > > >
> > > > Best Regards,
> > > > Jianheng
> > > >
> > > > [PATCH v2] net: stmmac: fix FPE events losing
> > > >
> > > > ---
> > > > drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 9 +++++++--
> > > > drivers/net/ethernet/stmicro/stmmac/dwmac5.h | 1 +
> > > > drivers/net/ethernet/stmicro/stmmac/hwif.h | 1 +
> > > > drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 6 +++++-
> > > > include/linux/stmmac.h | 1 +
> > > > 5 files changed, 15 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > index e95d35f..8917fd0 100644
> > > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > > @@ -736,12 +736,15 @@ void dwmac5_fpe_configure(void __iomem *ioaddr, u32 num_txq, u32
> > > num_rxq,
> > > >
> > > > int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
> > > > {
> > > > + struct stmmac_priv *priv = netdev_priv(dev);
> > > > + struct stmmac_fpe_cfg *fpe_cfg = priv->plat->fpe_cfg;
> > > > u32 value;
> > > > int status;
> > > >
> > > > status = FPE_EVENT_UNKNOWN;
> > > >
> > > > - value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > > > + value = readl(ioaddr + MAC_FPE_CTRL_STS) | fpe_cfg->staged_fpe_state;
> > > > + fpe_cfg->staged_fpe_state = 0x0;
> > > >
> > > > if (value & TRSP) {
> > > > status |= FPE_EVENT_TRSP;
> > > > @@ -766,11 +769,13 @@ 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;
> > > >
> > > > value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > > > + cfg->staged_fpe_state = value;
> > > >
> > > > if (type == MPACKET_VERIFY) {
> > > > value &= ~SRSP;
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > > b/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > > > index 53c138d..022c1a2 100644
> > > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > > > @@ -156,6 +156,7 @@ 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,
> > > > bool enable);
> > > > void dwmac5_fpe_send_mpacket(void __iomem *ioaddr,
> > > > + struct stmmac_fpe_cfg *cfg,
> > > > enum stmmac_mpacket_type type);
> > > > int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev);
> > > >
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > > b/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > > > index b95d3e1..5496781 100644
> > > > --- a/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > > > +++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > > > @@ -415,6 +415,7 @@ struct stmmac_ops {
> > > > void (*fpe_configure)(void __iomem *ioaddr, u32 num_txq, u32 num_rxq,
> > > > bool enable);
> > > > void (*fpe_send_mpacket)(void __iomem *ioaddr,
> > > > + struct stmmac_fpe_cfg *cfg,
> > > > enum stmmac_mpacket_type type);
> > > > int (*fpe_irq_status)(void __iomem *ioaddr, struct net_device *dev);
> > > > };
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > index 3e50fd5..6a29f55 100644
> > > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > @@ -964,7 +964,8 @@ static void stmmac_fpe_link_state_handle(struct stmmac_priv *priv, bool
> > > is_up)
> > > > bool *hs_enable = &fpe_cfg->hs_enable;
> > > >
> > > > if (is_up && *hs_enable) {
> > > > - stmmac_fpe_send_mpacket(priv, priv->ioaddr, MPACKET_VERIFY);
> > > > + stmmac_fpe_send_mpacket(priv, priv->ioaddr, fpe_cfg,
> > > > + MPACKET_VERIFY);
> > > > } else {
> > > > *lo_state = FPE_STATE_OFF;
> > > > *lp_state = FPE_STATE_OFF;
> > > > @@ -5838,6 +5839,7 @@ static void stmmac_fpe_event_status(struct stmmac_priv *priv, int
> status)
> > > > /* If user has requested FPE enable, quickly response */
> > > > if (*hs_enable)
> > > > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > > > + fpe_cfg,
> > > > MPACKET_RESPONSE);
> > > > }
> > > >
> > > > @@ -7280,6 +7282,7 @@ static void stmmac_fpe_lp_task(struct work_struct *work)
> > > > netdev_info(priv->dev, SEND_VERIFY_MPAKCET_FMT,
> > > > *lo_state, *lp_state);
> > > > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > > > + fpe_cfg,
> > > > MPACKET_VERIFY);
> > > > }
> > > > /* Sleep then retry */
> > > > @@ -7294,6 +7297,7 @@ void stmmac_fpe_handshake(struct stmmac_priv *priv, bool enable)
> > > > if (priv->plat->fpe_cfg->hs_enable != enable) {
> > > > if (enable) {
> > > > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > > > + priv->plat->fpe_cfg,
> > > > MPACKET_VERIFY);
> > > > } else {
> > > > priv->plat->fpe_cfg->lo_fpe_state = FPE_STATE_OFF;
> > > > diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> > > > index 0b4658a..1322c78 100644
> > > > --- a/include/linux/stmmac.h
> > > > +++ b/include/linux/stmmac.h
> > > > @@ -175,6 +175,7 @@ struct stmmac_fpe_cfg {
> > > > bool hs_enable; /* FPE handshake enable */
> > > > enum stmmac_fpe_state lp_fpe_state; /* Link Partner FPE state */
> > > > enum stmmac_fpe_state lo_fpe_state; /* Local station FPE state */
> > > > + u32 staged_fpe_state; /* Staged FPE state when read MAC_FPE_CTRL_STS */
> > > > };
> > > >
> > > > struct stmmac_safety_feature_cfg {
> > > > --
> > > > 1.8.3.1
> > > >
> >
> > Hi Serge,
> >
> > Thanks for your suggestion.
> >
> > > Are the status flags in the MAC_FPE_CTRL_STS register cleared on
> > > _writes_?
>
> > A write of 0 has no impact irrespective of the value programmed in RCWE bit.
> > This is safe option when writing the MAC_FPE_CTRL_STS register, which will
> > ensure that bits[19:16] are not modified unintentionally.
> > When RCWE bit is 0 and status bits[19:16] are read, those will be cleared, a write
> > of 0 or 1 do not have any impact in this mode.
>
> Great! Than always writing shall do the trick.
>
> >
> > > then what about just converting the
> > > dwmac5_fpe_configure() and dwmac5_fpe_send_mpacket() methods to always
> > > writing to the MAC_FPE_CTRL_STS register, and if required preserve the
> > > shadow control MAC_FPE_CTRL_STS flags in the stmmac_fpe_cfg structure?
> > > AFAICS the only flag which needs to be preserved is EFPE - "enable
> > > FPE" flag.
>
> > I think this is a good solution, pls check my draft patch below.
>
> Some comments are below.
>
> >
> > -Jianheng
> >
> > [PATCH v2] net: stmmac: fix FPE events losing
> >
> > ---
> > drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 26 +++++++++-------------
> > 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, 28 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > index e95d35f..9575e84 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > @@ -710,17 +710,15 @@ 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);
> > + writel(0x0, ioaddr + MAC_FPE_CTRL_STS);
> > + cfg->fpe_ctrl_sts_shadow = 0x0;
> > return;
> > }
> >
> > @@ -729,9 +727,9 @@ void dwmac5_fpe_configure(void __iomem *ioaddr, u32 num_txq, u32
> num_rxq,
> > value |= (num_rxq - 1) << GMAC_RXQCTRL_FPRQ_SHIFT;
> > writel(value, ioaddr + GMAC_RXQ_CTRL1);
> >
> > - value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > - value |= EFPE;
>
> > + value = EFPE;
> > writel(value, ioaddr + MAC_FPE_CTRL_STS);
> > + cfg->fpe_ctrl_sts_shadow = EFPE;
>
> What about just:
> if (enable)
> cfg->fpe_csr = EFPE;
> else
> cfg->fpe_csr = 0;
>
> writel(cfg->fpe_csr, ioaddr + MAC_FPE_CTRL_STS);
>
> then ...
>
> > }
> >
> > int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
> > @@ -766,19 +764,17 @@ 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;
> >
> > - value = readl(ioaddr + MAC_FPE_CTRL_STS);
> > + value = cfg->fpe_ctrl_sts_shadow;
> >
> > - if (type == MPACKET_VERIFY) {
> > - value &= ~SRSP;
> > + if (type == MPACKET_VERIFY)
> > value |= SVER;
> > - } else {
> > - value &= ~SVER;
> > + else
> > value |= SRSP;
> > - }
> >
> > writel(value, ioaddr + MAC_FPE_CTRL_STS);
>
> this can be replaced with
>
> u32 value = cfg->fpe_csr;
>
> if (type == MPACKET_VERIFY)
> value |= SVER;
> else if (type == MPACKET_RESPONSE)
> value |= SRSP;
>
> writel(value, ioaddr + MAC_FPE_CTRL_STS);
>
> > }
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> b/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > index 53c138d..aca846d 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.h
> > @@ -153,9 +153,11 @@ int dwmac5_est_configure(void __iomem *ioaddr, struct stmmac_est *cfg,
> > unsigned int ptp_rate);
> > void dwmac5_est_irq_status(void __iomem *ioaddr, struct net_device *dev,
> > struct stmmac_extra_stats *x, u32 txqcnt);
> > -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);
> > void dwmac5_fpe_send_mpacket(void __iomem *ioaddr,
> > + struct stmmac_fpe_cfg *cfg,
> > enum stmmac_mpacket_type type);
> > int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev);
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
> b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
> > index 453e88b..a74e71d 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
> > @@ -1484,7 +1484,8 @@ static int dwxgmac3_est_configure(void __iomem *ioaddr, struct
> stmmac_est *cfg,
> > return 0;
> > }
> >
> > -static void dwxgmac3_fpe_configure(void __iomem *ioaddr, u32 num_txq,
> > +static void dwxgmac3_fpe_configure(void __iomem *ioaddr, struct stmmac_fpe_cfg *cfg,
> > + u32 num_txq,
> > u32 num_rxq, bool enable)
> > {
> > u32 value;
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h
> b/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > index b95d3e1..68aa2d5 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > +++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h
> > @@ -412,9 +412,11 @@ struct stmmac_ops {
> > unsigned int ptp_rate);
> > void (*est_irq_status)(void __iomem *ioaddr, struct net_device *dev,
> > struct stmmac_extra_stats *x, u32 txqcnt);
> > - void (*fpe_configure)(void __iomem *ioaddr, u32 num_txq, u32 num_rxq,
> > + void (*fpe_configure)(void __iomem *ioaddr, struct stmmac_fpe_cfg *cfg,
> > + u32 num_txq, u32 num_rxq,
> > bool enable);
> > void (*fpe_send_mpacket)(void __iomem *ioaddr,
> > + struct stmmac_fpe_cfg *cfg,
> > enum stmmac_mpacket_type type);
> > int (*fpe_irq_status)(void __iomem *ioaddr, struct net_device *dev);
> > };
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 3e50fd5..7791e9b 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -964,7 +964,8 @@ static void stmmac_fpe_link_state_handle(struct stmmac_priv *priv, bool
> is_up)
> > bool *hs_enable = &fpe_cfg->hs_enable;
> >
> > if (is_up && *hs_enable) {
> > - stmmac_fpe_send_mpacket(priv, priv->ioaddr, MPACKET_VERIFY);
> > + stmmac_fpe_send_mpacket(priv, priv->ioaddr, fpe_cfg,
> > + MPACKET_VERIFY);
> > } else {
> > *lo_state = FPE_STATE_OFF;
> > *lp_state = FPE_STATE_OFF;
> > @@ -5838,6 +5839,7 @@ static void stmmac_fpe_event_status(struct stmmac_priv *priv, int status)
> > /* If user has requested FPE enable, quickly response */
> > if (*hs_enable)
> > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > + fpe_cfg,
> > MPACKET_RESPONSE);
> > }
> >
> > @@ -7262,6 +7264,7 @@ static void stmmac_fpe_lp_task(struct work_struct *work)
> > if (*lo_state == FPE_STATE_ENTERING_ON &&
> > *lp_state == FPE_STATE_ENTERING_ON) {
> > stmmac_fpe_configure(priv, priv->ioaddr,
> > + fpe_cfg,
> > priv->plat->tx_queues_to_use,
> > priv->plat->rx_queues_to_use,
> > *enable);
> > @@ -7280,6 +7283,7 @@ static void stmmac_fpe_lp_task(struct work_struct *work)
> > netdev_info(priv->dev, SEND_VERIFY_MPAKCET_FMT,
> > *lo_state, *lp_state);
> > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > + fpe_cfg,
> > MPACKET_VERIFY);
> > }
> > /* Sleep then retry */
> > @@ -7294,6 +7298,7 @@ void stmmac_fpe_handshake(struct stmmac_priv *priv, bool enable)
> > if (priv->plat->fpe_cfg->hs_enable != enable) {
> > if (enable) {
> > stmmac_fpe_send_mpacket(priv, priv->ioaddr,
> > + priv->plat->fpe_cfg,
> > MPACKET_VERIFY);
> > } else {
> > priv->plat->fpe_cfg->lo_fpe_state = FPE_STATE_OFF;
> > @@ -7754,6 +7759,7 @@ int stmmac_suspend(struct device *dev)
> > if (priv->dma_cap.fpesel) {
> > /* Disable FPE */
> > stmmac_fpe_configure(priv, priv->ioaddr,
> > + priv->plat->fpe_cfg,
> > priv->plat->tx_queues_to_use,
> > priv->plat->rx_queues_to_use, false);
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > index ac41ef4..6ad3e0a 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > @@ -1079,6 +1079,7 @@ static int tc_setup_taprio(struct stmmac_priv *priv,
> >
> > priv->plat->fpe_cfg->enable = false;
> > stmmac_fpe_configure(priv, priv->ioaddr,
> > + priv->plat->fpe_cfg,
> > priv->plat->tx_queues_to_use,
> > priv->plat->rx_queues_to_use,
> > false);
> > diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> > index 0b4658a..48385c7 100644
> > --- a/include/linux/stmmac.h
> > +++ b/include/linux/stmmac.h
> > @@ -175,6 +175,7 @@ struct stmmac_fpe_cfg {
> > bool hs_enable; /* FPE handshake enable */
> > enum stmmac_fpe_state lp_fpe_state; /* Link Partner FPE state */
> > enum stmmac_fpe_state lo_fpe_state; /* Local station FPE state */
>
> > + u32 fpe_ctrl_sts_shadow; /* shadow of MAC_FPE_CTRL_STS */
>
> + u32 fpe_csr; /* MAC_FPE_CTRL_STS reg cache */
>
> I would have had it named as "fpe_csr" - short and well readable
> especially seeing CSR is a well known abbreviation for Control and
> Status register, which the MAC_FPE_CTRL_STS register actually is.
>
> * Note one more time: current FPE handshaking implementation is vastly
> clumsy, needlessly overcomplicated and prone to races. I would have
> seriously considered having it refactored.
>
> -Serge(y)
>
> > };
> >
> > struct stmmac_safety_feature_cfg {
> > --
> > 1.8.3.1
> >

Hi Serge，

Thanks for your comments and for pointing out the defects of the current FPE
handshaking implementation. I know that my patch cannot solve all the
defects of the current FPE handshaking. So, I want to know if it is necessary
that I continue submitting this patch if you want to refactor the FPE
handshaking further. Moreover, I want to add FPE handshaking support for DW
XGMAC (add fpe_send_mpacket() & fpe_irq_status() to dwxlgmac2_core.c) after
fixing this MAC_FPE_CTRL_STS register read issue.

-Jianheng

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