[PATCH 5.15 094/136] net: stmmac: work around sporadic tx issue on link-up

Greg Kroah-Hartman
2022-08-29T11:17:43Z

From: Heiner Kallweit <hkallweit1@gmail.com>

[ Upstream commit a3a57bf07de23fe1ff779e0fdf710aa581c3ff73 ]

This is a follow-up to the discussion in [0]. It seems to me that
at least the IP version used on Amlogic SoC's sometimes has a problem
if register MAC_CTRL_REG is written whilst the chip is still processing
a previous write. But that's just a guess.
Adding a delay between two writes to this register helps, but we can
also simply omit the offending second write. This patch uses the second
approach and is based on a suggestion from Qi Duan.
Benefit of this approach is that we can save few register writes, also
on not affected chip versions.

[0] https://www.spinics.net/lists/netdev/msg831526.html

Fixes: bfab27a146ed ("stmmac: add the experimental PCI support")
Suggested-by: Qi Duan <qi.duan@amlogic.com>
Suggested-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/e99857ce-bd90-5093-ca8c-8cd480b5a0a2@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c | 8 ++++++--
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 +++++----
2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
index d1c31200bb911..01d0a14f67520 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
@@ -258,14 +258,18 @@ EXPORT_SYMBOL_GPL(stmmac_set_mac_addr);
/* Enable disable MAC RX/TX */
void stmmac_set_mac(void __iomem *ioaddr, bool enable)
{
- u32 value = readl(ioaddr + MAC_CTRL_REG);
+ u32 old_val, value;
+
+ old_val = readl(ioaddr + MAC_CTRL_REG);
+ value = old_val;

if (enable)
value |= MAC_ENABLE_RX | MAC_ENABLE_TX;
else
value &= ~(MAC_ENABLE_TX | MAC_ENABLE_RX);

- writel(value, ioaddr + MAC_CTRL_REG);
+ if (value != old_val)
+ writel(value, ioaddr + MAC_CTRL_REG);
}

void stmmac_get_mac_addr(void __iomem *ioaddr, unsigned char *addr,
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b4f83c8655684..2569673559df3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1083,10 +1083,10 @@ static void stmmac_mac_link_up(struct phylink_config *config,
bool tx_pause, bool rx_pause)
{
struct stmmac_priv *priv = netdev_priv(to_net_dev(config->dev));
- u32 ctrl;
+ u32 old_ctrl, ctrl;

- ctrl = readl(priv->ioaddr + MAC_CTRL_REG);
- ctrl &= ~priv->hw->link.speed_mask;
+ old_ctrl = readl(priv->ioaddr + MAC_CTRL_REG);
+ ctrl = old_ctrl & ~priv->hw->link.speed_mask;

if (interface == PHY_INTERFACE_MODE_USXGMII) {
switch (speed) {
@@ -1161,7 +1161,8 @@ static void stmmac_mac_link_up(struct phylink_config *config,
if (tx_pause && rx_pause)
stmmac_mac_flow_ctrl(priv, duplex);

- writel(ctrl, priv->ioaddr + MAC_CTRL_REG);
+ if (ctrl != old_ctrl)
+ writel(ctrl, priv->ioaddr + MAC_CTRL_REG);

stmmac_mac_set(priv, priv->ioaddr, true);
if (phy && priv->dma_cap.eee) {
--
2.35.1