[PATCH net-next v2 13/14] net: stmmac: check txpbl for TSO

[Russell King (Oracle)]

Documentation states that TxPBL must be >= 4 to allow TSO support, but
the driver doesn't check this. TxPBL comes from the platform glue code
or DT. Add a check with a warning if platform glue code attempts to
enable TSO support with TxPBL too low.

Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 5286ad6412a3..406c32142d90 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4388,6 +4388,8 @@ static void stmmac_set_gso_types(struct stmmac_priv *priv, bool tso)
 static void stmmac_set_gso_features(struct net_device *ndev)
 {
 	struct stmmac_priv *priv = netdev_priv(ndev);
+	const struct stmmac_dma_cfg *dma_cfg;
+	int txpbl;
 
 	if (!(priv->plat->flags & STMMAC_FLAG_TSO_EN))
 		return;
@@ -4397,6 +4399,18 @@ static void stmmac_set_gso_features(struct net_device *ndev)
 		return;
 	}
 
+	/* FIXME:
+	 *  STM32MP151 (v4.2 userver v4.0) states that TxPBL must be >= 4. It
+	 *  is not clear whether PBLx8 (which multiplies the PBL value by 8)
+	 *  influences this.
+	 */
+	dma_cfg = priv->plat->dma_cfg;
+	txpbl = dma_cfg->txpbl ?: dma_cfg->pbl;
+	if (txpbl < 4) {
+		dev_warn(priv->device, "txpbl(%d) is too low for TSO\n", txpbl);
+		return;
+	}
+
 	ndev->hw_features |= NETIF_F_TSO | NETIF_F_TSO6;
 	if (priv->plat->core_type == DWMAC_CORE_GMAC4)
 		ndev->hw_features |= NETIF_F_GSO_UDP_L4;
-- 
2.47.3