linux-kernel - [PATCH net] net: stmmac: Apply redundant write work around on 4.xx too

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Date:   Fri, 21 Jul 2023 15:39:20 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        "Jakub Kicinski" <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>
CC:     <netdev@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>
Subject: [PATCH net] net: stmmac: Apply redundant write work around on 4.xx
 too

commit a3a57bf07de23fe1ff779e0fdf710aa581c3ff73 ("net: stmmac: work
around sporadic tx issue on link-up") worked around a problem with TX
sometimes not working after a link-up by avoiding a redundant write to
MAC_CTRL_REG (aka GMAC_CONFIG), since the IP appeared to have problems
with handling multiple writes to that register in some cases.

That commit however only added the work around to dwmac_lib.c (apart
from the common code in stmmac_main.c), but my systems with version
4.21a of the IP exhibit the same problem, so add the work around to
dwmac4_lib.c too.

Fixes: a3a57bf07de2 ("net: stmmac: work around sporadic tx issue on link-up")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
index df41eac54058..03ceb6a94073 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
@@ -240,13 +240,15 @@ void stmmac_dwmac4_set_mac_addr(void __iomem *ioaddr, const u8 addr[6],
 void stmmac_dwmac4_set_mac(void __iomem *ioaddr, bool enable)
 {
 	u32 value = readl(ioaddr + GMAC_CONFIG);
+	u32 old_val = value;
 
 	if (enable)
 		value |= GMAC_CONFIG_RE | GMAC_CONFIG_TE;
 	else
 		value &= ~(GMAC_CONFIG_TE | GMAC_CONFIG_RE);
 
-	writel(value, ioaddr + GMAC_CONFIG);
+	if (value != old_val)
+		writel(value, ioaddr + GMAC_CONFIG);
 }
 
 void stmmac_dwmac4_get_mac_addr(void __iomem *ioaddr, unsigned char *addr,

---
base-commit: fdf0eaf11452d72945af31804e2a1048ee1b574c
change-id: 20230721-stmmac-tx-workaround-fb17741c326e

Best regards,
-- 
Vincent Whitchurch <vincent.whitchurch@...s.com>