[PATCH 1/2] stmmac: introduce flag to dynamically disable TX offload for rockchip devices

["Leonidas P. Papadakos" <papadakospan@gmail.com>]

From: =?UTF-8?q?Kamil=20Trzci=C5=84ski?= <ayufan@ayufan.eu>

Some rockchip boards exhibit an issue where tx checksumming does not work with
packets larger than 1498.

This is bad for network stability.

The previous approach was using force_thresh_dma_mode in the board dts, which
does more than we need.

Signed-off-by: Leonidas P. Papadakos <papadakospan@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     | 4 ++++
 drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 2 ++
 include/linux/stmmac.h                                | 1 +
 3 files changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 6a2e1031a..4552147e9 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3660,6 +3660,10 @@ static netdev_features_t stmmac_fix_features(struct net_device *dev,
 	if (priv->plat->bugged_jumbo && (dev->mtu > ETH_DATA_LEN))
 		features &= ~NETIF_F_CSUM_MASK;
 
+	/* Including very small MTUs of 1498 for Rockchip devices */
+	if (priv->plat->bugged_tx_coe && (dev->mtu > ETH_DATA_LEN - 2))
+		features &= ~NETIF_F_CSUM_MASK;
+
 	/* Disable tso if asked by ethtool */
 	if ((priv->plat->tso_en) && (priv->dma_cap.tsoen)) {
 		if (features & NETIF_F_TSO)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
index 3031f2bf1..807cf5826 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
@@ -519,6 +519,8 @@ stmmac_probe_config_dt(struct platform_device *pdev, const char **mac)
 		pr_warn("force_sf_dma_mode is ignored if force_thresh_dma_mode is set.");
 	}
 
+	plat->bugged_tx_coe = of_property_read_bool(np, "rockchip,bugged_tx_coe");
+
 	of_property_read_u32(np, "snps,ps-speed", &plat->mac_port_sel_speed);
 
 	plat->axi = stmmac_axi_setup(pdev);
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index 4335bd771..60c411f43 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h
@@ -162,6 +162,7 @@ struct plat_stmmacenet_data {
 	int pmt;
 	int force_sf_dma_mode;
 	int force_thresh_dma_mode;
+	int bugged_tx_coe;
 	int riwt_off;
 	int max_speed;
 	int maxmtu;
-- 
2.21.0