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Message-ID: <ZxE9+iaz+QI9Jeak@lizhi-Precision-Tower-5810>
Date: Thu, 17 Oct 2024 12:40:26 -0400
From: Frank Li <Frank.li@....com>
To: Wei Fang <wei.fang@....com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, robh@...nel.org, krzk+dt@...nel.org,
conor+dt@...nel.org, vladimir.oltean@....com,
claudiu.manoil@....com, xiaoning.wang@....com,
christophe.leroy@...roup.eu, linux@...linux.org.uk,
bhelgaas@...gle.com, horms@...nel.org, imx@...ts.linux.dev,
netdev@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 net-next 07/13] net: enetc: remove ERR050089
workaround for i.MX95
On Thu, Oct 17, 2024 at 03:46:31PM +0800, Wei Fang wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
>
> The ERR050089 workaround causes performance degradation and potential
> functional issues (e.g., RCU stalls) under certain workloads. Since
> new SoCs like i.MX95 do not require this workaround, use a static key
> to compile out enetc_lock_mdio() and enetc_unlock_mdio() at runtime,
> improving performance and avoiding unnecessary logic.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Signed-off-by: Wei Fang <wei.fang@....com>
Reviewed-by: Frank Li <Frank.Li@....com>
> ---
> v2 changes: no changes
> v3 changes: Change the title and refactor the commit message.
> ---
> .../net/ethernet/freescale/enetc/enetc_hw.h | 34 +++++++++++++------
> .../ethernet/freescale/enetc/enetc_pci_mdio.c | 17 ++++++++++
> 2 files changed, 41 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_hw.h b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
> index 1619943fb263..6a7b9b75d660 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_hw.h
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
> @@ -396,18 +396,22 @@ struct enetc_hw {
> */
> extern rwlock_t enetc_mdio_lock;
>
> +DECLARE_STATIC_KEY_FALSE(enetc_has_err050089);
> +
> /* use this locking primitive only on the fast datapath to
> * group together multiple non-MDIO register accesses to
> * minimize the overhead of the lock
> */
> static inline void enetc_lock_mdio(void)
> {
> - read_lock(&enetc_mdio_lock);
> + if (static_branch_unlikely(&enetc_has_err050089))
> + read_lock(&enetc_mdio_lock);
> }
>
> static inline void enetc_unlock_mdio(void)
> {
> - read_unlock(&enetc_mdio_lock);
> + if (static_branch_unlikely(&enetc_has_err050089))
> + read_unlock(&enetc_mdio_lock);
> }
>
> /* use these accessors only on the fast datapath under
> @@ -416,14 +420,16 @@ static inline void enetc_unlock_mdio(void)
> */
> static inline u32 enetc_rd_reg_hot(void __iomem *reg)
> {
> - lockdep_assert_held(&enetc_mdio_lock);
> + if (static_branch_unlikely(&enetc_has_err050089))
> + lockdep_assert_held(&enetc_mdio_lock);
>
> return ioread32(reg);
> }
>
> static inline void enetc_wr_reg_hot(void __iomem *reg, u32 val)
> {
> - lockdep_assert_held(&enetc_mdio_lock);
> + if (static_branch_unlikely(&enetc_has_err050089))
> + lockdep_assert_held(&enetc_mdio_lock);
>
> iowrite32(val, reg);
> }
> @@ -452,9 +458,13 @@ static inline u32 _enetc_rd_mdio_reg_wa(void __iomem *reg)
> unsigned long flags;
> u32 val;
>
> - write_lock_irqsave(&enetc_mdio_lock, flags);
> - val = ioread32(reg);
> - write_unlock_irqrestore(&enetc_mdio_lock, flags);
> + if (static_branch_unlikely(&enetc_has_err050089)) {
> + write_lock_irqsave(&enetc_mdio_lock, flags);
> + val = ioread32(reg);
> + write_unlock_irqrestore(&enetc_mdio_lock, flags);
> + } else {
> + val = ioread32(reg);
> + }
>
> return val;
> }
> @@ -463,9 +473,13 @@ static inline void _enetc_wr_mdio_reg_wa(void __iomem *reg, u32 val)
> {
> unsigned long flags;
>
> - write_lock_irqsave(&enetc_mdio_lock, flags);
> - iowrite32(val, reg);
> - write_unlock_irqrestore(&enetc_mdio_lock, flags);
> + if (static_branch_unlikely(&enetc_has_err050089)) {
> + write_lock_irqsave(&enetc_mdio_lock, flags);
> + iowrite32(val, reg);
> + write_unlock_irqrestore(&enetc_mdio_lock, flags);
> + } else {
> + iowrite32(val, reg);
> + }
> }
>
> #ifdef ioread64
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c b/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
> index a1b595bd7993..2445e35a764a 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c
> @@ -9,6 +9,9 @@
> #define ENETC_MDIO_BUS_NAME ENETC_MDIO_DEV_NAME " Bus"
> #define ENETC_MDIO_DRV_NAME ENETC_MDIO_DEV_NAME " driver"
>
> +DEFINE_STATIC_KEY_FALSE(enetc_has_err050089);
> +EXPORT_SYMBOL_GPL(enetc_has_err050089);
> +
> static int enetc_pci_mdio_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
> {
> @@ -62,6 +65,12 @@ static int enetc_pci_mdio_probe(struct pci_dev *pdev,
> goto err_pci_mem_reg;
> }
>
> + if (pdev->vendor == PCI_VENDOR_ID_FREESCALE &&
> + pdev->device == ENETC_MDIO_DEV_ID) {
> + static_branch_inc(&enetc_has_err050089);
> + dev_info(&pdev->dev, "Enabled ERR050089 workaround\n");
> + }
> +
> err = of_mdiobus_register(bus, dev->of_node);
> if (err)
> goto err_mdiobus_reg;
> @@ -88,6 +97,14 @@ static void enetc_pci_mdio_remove(struct pci_dev *pdev)
> struct enetc_mdio_priv *mdio_priv;
>
> mdiobus_unregister(bus);
> +
> + if (pdev->vendor == PCI_VENDOR_ID_FREESCALE &&
> + pdev->device == ENETC_MDIO_DEV_ID) {
> + static_branch_dec(&enetc_has_err050089);
> + if (!static_key_enabled(&enetc_has_err050089.key))
> + dev_info(&pdev->dev, "Disabled ERR050089 workaround\n");
> + }
> +
> mdio_priv = bus->priv;
> iounmap(mdio_priv->hw->port);
> pci_release_region(pdev, 0);
> --
> 2.34.1
>
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