Call stmmac_fpe_supported() to check both HW capability and
driver capability to keep FPE as an optional implementation
for current and new MAC cores.

Signed-off-by: Furong Xu <0x1207@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c |  2 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c     | 10 ++++++++++
 drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.h     |  1 +
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c    | 10 +++++-----
 4 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
index f2783f7c46f3..1d77389ce953 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
@@ -1271,7 +1271,7 @@ static int stmmac_get_mm(struct net_device *ndev,
 	unsigned long flags;
 	u32 frag_size;
 
-	if (!priv->dma_cap.fpesel)
+	if (!stmmac_fpe_supported(priv))
 		return -EOPNOTSUPP;
 
 	spin_lock_irqsave(&priv->fpe_cfg.lock, flags);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
index 818741579904..fe0877ef5f4f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
@@ -42,6 +42,12 @@ struct stmmac_fpe_reg {
 	const u32 int_en_bit;		/* Frame Preemption Interrupt Enable */
 };
 
+bool stmmac_fpe_supported(struct stmmac_priv *priv)
+{
+	return priv->dma_cap.fpesel && priv->fpe_cfg.reg &&
+		priv->hw->mac->fpe_map_preemption_class;
+}
+
 void stmmac_fpe_link_state_handle(struct stmmac_priv *priv, bool is_up)
 {
 	struct stmmac_fpe_cfg *fpe_cfg = &priv->fpe_cfg;
@@ -173,6 +179,10 @@ void stmmac_fpe_init(struct stmmac_priv *priv)
 	priv->fpe_cfg.status = ETHTOOL_MM_VERIFY_STATUS_DISABLED;
 	timer_setup(&priv->fpe_cfg.verify_timer, stmmac_fpe_verify_timer, 0);
 	spin_lock_init(&priv->fpe_cfg.lock);
+
+	if ((!priv->fpe_cfg.reg || !priv->hw->mac->fpe_map_preemption_class) &&
+	    priv->dma_cap.fpesel)
+		dev_info(priv->device, "FPE on this MAC is not supported by driver.\n");
 }
 
 void stmmac_fpe_apply(struct stmmac_priv *priv)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.h
index 15fcb9ef1a97..2f8bceaf7a0a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.h
@@ -16,6 +16,7 @@ struct stmmac_priv;
 struct stmmac_fpe_cfg;
 
 void stmmac_fpe_link_state_handle(struct stmmac_priv *priv, bool is_up);
+bool stmmac_fpe_supported(struct stmmac_priv *priv);
 void stmmac_fpe_init(struct stmmac_priv *priv);
 void stmmac_fpe_apply(struct stmmac_priv *priv);
 void stmmac_fpe_configure(struct stmmac_priv *priv, bool tx_enable,
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9fcf2df099ec..883b4b814125 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -978,7 +978,7 @@ static void stmmac_mac_link_down(struct phylink_config *config,
 	priv->eee_enabled = stmmac_eee_init(priv);
 	stmmac_set_eee_pls(priv, priv->hw, false);
 
-	if (priv->dma_cap.fpesel)
+	if (stmmac_fpe_supported(priv))
 		stmmac_fpe_link_state_handle(priv, false);
 }
 
@@ -1092,7 +1092,7 @@ static void stmmac_mac_link_up(struct phylink_config *config,
 		stmmac_set_eee_pls(priv, priv->hw, true);
 	}
 
-	if (priv->dma_cap.fpesel)
+	if (stmmac_fpe_supported(priv))
 		stmmac_fpe_link_state_handle(priv, true);
 
 	if (priv->plat->flags & STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY)
@@ -4040,7 +4040,7 @@ static int stmmac_release(struct net_device *dev)
 
 	stmmac_release_ptp(priv);
 
-	if (priv->dma_cap.fpesel)
+	if (stmmac_fpe_supported(priv))
 		timer_shutdown_sync(&priv->fpe_cfg.verify_timer);
 
 	pm_runtime_put(priv->device);
@@ -5943,7 +5943,7 @@ static void stmmac_common_interrupt(struct stmmac_priv *priv)
 		stmmac_est_irq_status(priv, priv, priv->dev,
 				      &priv->xstats, tx_cnt);
 
-	if (priv->dma_cap.fpesel)
+	if (stmmac_fpe_supported(priv))
 		stmmac_fpe_irq_status(priv);
 
 	/* To handle GMAC own interrupts */
@@ -7729,7 +7729,7 @@ int stmmac_suspend(struct device *dev)
 	}
 	rtnl_unlock();
 
-	if (priv->dma_cap.fpesel)
+	if (stmmac_fpe_supported(priv))
 		timer_shutdown_sync(&priv->fpe_cfg.verify_timer);
 
 	priv->speed = SPEED_UNKNOWN;
-- 
2.34.1

On Thu, Oct 31, 2024 at 08:37:58PM +0800, Furong Xu wrote:
> Call stmmac_fpe_supported() to check both HW capability and
> driver capability to keep FPE as an optional implementation
> for current and new MAC cores.
> 
> Signed-off-by: Furong Xu <0x1207@gmail.com>
> ---

Doesn't this commit actually fix a bug which patch 3/8 introduced?
If priv->fpe_cfg.reg is NULL, we will dereference that after just
patch 3/8 has been applied. During e.g. a git bisect landing in between,
that crash might be seen by users.

Thus, please reorder these 2 patches to prevent the bug from existing in
the first place, and say in the commit message that the reason for the
introduction of stmmac_fpe_supported() - initially simply implemented as
a single "priv->dma_cap.fpesel" check - is to prevent unexpected
behavior on unsupported FPE MACs during further refactoring.

Then, the patch "net: stmmac: Refactor FPE functions to generic version"
should be the one which also reimplements stmmac_fpe_supported() to
check for the presence of the newly added primitives.