[PATCH net-next v2 0/3] net: stmmac: fpe: pmac and fprq fixes

[PATCH net-next v2 0/3] net: stmmac: fpe: pmac and fprq fixes

[muhammad.nazim.amirul.nazle.asmade]

From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>

Three fixes for the stmmac FPE implementation:

- Keep pmac_enabled true in DWMAC since the preemptive MAC is always
  on, enforce this in set_mm(), and guard set_mm() with fpesel check
- Fix missing return in stmmac_fpe_init() when FPE is unsupported
- Move fprq configuration to stmmac_fpe_configure_pmac() where it
  belongs

v2:
  - Drop u32_replace_bits() in patch 3; fprq_mask is not a compile-time
    constant and triggered __bad_mask on x86 builds. Keep the open-coded
    mask/shift update instead.
  - Collect Reviewed-by from Maxime Chevallier.

Nazim Amirul (3):
  net: stmmac: fpe: Enforce pmac_enabled in set_mm and keep it on at
    init
  net: stmmac: fpe: Add missing return in stmmac_fpe_init()
  net: stmmac: fpe: Move fprq configuration to
    stmmac_fpe_configure_pmac()

 .../ethernet/stmicro/stmmac/stmmac_ethtool.c  |  7 +++++
 .../net/ethernet/stmicro/stmmac/stmmac_fpe.c  | 34 +++++++++++++-------
 2 files changed, 29 insertions(+), 12 deletions(-)

-- 
2.43.7

[PATCH net-next v2 1/3] net: stmmac: fpe: Enforce pmac_enabled in set_mm and keep it on at init

[muhammad.nazim.amirul.nazle.asmade]

From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>

The preemptive MAC in DWMAC is always enabled, meaning DWMAC is always
ready to receive preemptive mPackets. Initialize pmac_enabled to true
at init time and reject attempts to disable it via ethtool set_mm.

Also add a missing fpesel capability check in stmmac_set_mm() to return
-EOPNOTSUPP early on hardware without FPE support.

Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
v2: No changes. Collect Reviewed-by from Maxime Chevallier.

 drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c | 7 +++++++
 drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c     | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
index 92585d27ab88..8ebdd249e5c8 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
@@ -1064,6 +1064,13 @@ static int stmmac_set_mm(struct net_device *ndev, struct ethtool_mm_cfg *cfg,
 	if (err)
 		return err;
 
+	if (!priv->dma_cap.fpesel)
+		return -EOPNOTSUPP;
+
+	/* DWMAC always have preemptible MAC enabled */
+	if (!cfg->pmac_enabled)
+		return -EINVAL;
+
 	stmmac_fpe_set_add_frag_size(priv, frag_size);
 	ethtool_mmsv_set_mm(&priv->fpe_cfg.mmsv, cfg);
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
index c54c70224351..2f880c5e35b0 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
@@ -176,6 +176,11 @@ void stmmac_fpe_init(struct stmmac_priv *priv)
 	if ((!priv->fpe_cfg.reg || !priv->hw->mac->fpe_map_preemption_class) &&
 	    priv->dma_cap.fpesel)
 		dev_info(priv->device, "FPE is not supported by driver.\n");
+
+	/* The preemptive MAC in DWMAC is always enabled, so initialize
+	 * pmac_enabled to true to reflect the hardware state.
+	 */
+	priv->fpe_cfg.mmsv.pmac_enabled = true;
 }
 
 int stmmac_fpe_get_add_frag_size(struct stmmac_priv *priv)
-- 
2.43.7

[PATCH net-next v2 2/3] net: stmmac: fpe: Add missing return in stmmac_fpe_init()

[muhammad.nazim.amirul.nazle.asmade]

From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>

When FPE is not supported by the driver, stmmac_fpe_init() prints a
warning but falls through into the pmac_enabled initialization, which
should only be reached on supported hardware. Add the missing return
to prevent this.

Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
v2: No changes. Collect Reviewed-by from Maxime Chevallier.

 drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
index 2f880c5e35b0..3436e962a238 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
@@ -174,8 +174,10 @@ void stmmac_fpe_init(struct stmmac_priv *priv)
 			  &stmmac_mmsv_ops);
 
 	if ((!priv->fpe_cfg.reg || !priv->hw->mac->fpe_map_preemption_class) &&
-	    priv->dma_cap.fpesel)
+	    priv->dma_cap.fpesel) {
 		dev_info(priv->device, "FPE is not supported by driver.\n");
+		return;
+	}
 
 	/* The preemptive MAC in DWMAC is always enabled, so initialize
 	 * pmac_enabled to true to reflect the hardware state.
-- 
2.43.7

Re: [PATCH net-next v2 2/3] net: stmmac: fpe: Add missing return in stmmac_fpe_init()

[Paolo Abeni]

On 8/3/26 5:23 AM, muhammad.nazim.amirul.nazle.asmade@altera.com wrote:
> From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
> 
> When FPE is not supported by the driver, stmmac_fpe_init() prints a
> warning but falls through into the pmac_enabled initialization, which
> should only be reached on supported hardware. Add the missing return
> to prevent this.
> 
> Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
> Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
> Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> ---
> v2: No changes. Collect Reviewed-by from Maxime Chevallier.
> 
>  drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
> index 2f880c5e35b0..3436e962a238 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
> @@ -174,8 +174,10 @@ void stmmac_fpe_init(struct stmmac_priv *priv)
>  			  &stmmac_mmsv_ops);
>  
>  	if ((!priv->fpe_cfg.reg || !priv->hw->mac->fpe_map_preemption_class) &&
> -	    priv->dma_cap.fpesel)
> +	    priv->dma_cap.fpesel) {

Sashiko noted that the above condition does not reach the intended effect:

https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260803032358.16282-1-muhammad.nazim.amirul.nazle.asmade%40altera.com

Also please be aware of net-next commit c82ff94592fb

/P

[PATCH net-next v2 3/3] net: stmmac: fpe: Move fprq configuration to stmmac_fpe_configure_pmac()

[muhammad.nazim.amirul.nazle.asmade]

From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>

The Frame Preemption Residue Queue (fprq) controls which Rx queue
receives residual preemptive mPackets from the pmac. This is a pmac
concern, not a TX concern, so move its configuration from
stmmac_fpe_configure_tx() to stmmac_fpe_configure_pmac() where it
logically belongs.

Keep the open-coded mask/shift update rather than u32_replace_bits(),
since fprq_mask is not a compile-time constant.

Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@altera.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
v2: Drop u32_replace_bits(); fprq_mask is not a compile-time constant
    and triggered __bad_mask on x86. Keep open-coded mask/shift.
    Collect Reviewed-by from Maxime Chevallier.

 .../net/ethernet/stmicro/stmmac/stmmac_fpe.c  | 24 ++++++++++---------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
index 3436e962a238..55b4df3c677b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
@@ -47,20 +47,13 @@ static void stmmac_fpe_configure_tx(struct ethtool_mmsv *mmsv, bool tx_enable)
 	struct stmmac_fpe_cfg *cfg = container_of(mmsv, struct stmmac_fpe_cfg, mmsv);
 	struct stmmac_priv *priv = container_of(cfg, struct stmmac_priv, fpe_cfg);
 	const struct stmmac_fpe_reg *reg = cfg->reg;
-	u32 num_rxq = priv->plat->rx_queues_to_use;
 	void __iomem *ioaddr = priv->ioaddr;
-	u32 value;
 
-	if (tx_enable) {
+	if (tx_enable)
 		cfg->fpe_csr = STMMAC_MAC_FPE_CTRL_STS_EFPE;
-		value = readl(ioaddr + reg->rxq_ctrl1_reg);
-		value &= ~reg->fprq_mask;
-		/* Keep this SHIFT, FIELD_PREP() expects a constant mask :-/ */
-		value |= (num_rxq - 1) << __ffs(reg->fprq_mask);
-		writel(value, ioaddr + reg->rxq_ctrl1_reg);
-	} else {
+	else
 		cfg->fpe_csr = 0;
-	}
+
 	writel(cfg->fpe_csr, ioaddr + reg->mac_fpe_reg);
 }
 
@@ -68,10 +61,11 @@ static void stmmac_fpe_configure_pmac(struct ethtool_mmsv *mmsv, bool pmac_enabl
 {
 	struct stmmac_fpe_cfg *cfg = container_of(mmsv, struct stmmac_fpe_cfg, mmsv);
 	struct stmmac_priv *priv = container_of(cfg, struct stmmac_priv, fpe_cfg);
+	u32 num_rxq = priv->plat->rx_queues_to_use;
 	const struct stmmac_fpe_reg *reg = cfg->reg;
 	void __iomem *ioaddr = priv->ioaddr;
 	unsigned long flags;
-	u32 value;
+	u32 value, value_2;
 
 	spin_lock_irqsave(&priv->hw->irq_ctrl_lock, flags);
 	value = readl(ioaddr + reg->int_en_reg);
@@ -83,6 +77,14 @@ static void stmmac_fpe_configure_pmac(struct ethtool_mmsv *mmsv, bool pmac_enabl
 
 			value |= reg->int_en_bit;
 		}
+		/* Frame Preemption Residue Queue is the Rx Queue to which
+		 * residual preemptive mPackets must be forwarded from the pmac.
+		 */
+		value_2 = readl(ioaddr + reg->rxq_ctrl1_reg);
+		value_2 &= ~reg->fprq_mask;
+		/* Keep this SHIFT, FIELD_PREP() expects a constant mask :-/ */
+		value_2 |= (num_rxq - 1) << __ffs(reg->fprq_mask);
+		writel(value_2, ioaddr + reg->rxq_ctrl1_reg);
 	} else {
 		value &= ~reg->int_en_bit;
 	}
-- 
2.43.7