netdev - [PATCH net-next v2 13/18] net: macb: avoid double endianness swap in macb_set

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Message-Id: <20250627-macb-v2-13-ff8207d0bb77@bootlin.com>
Date: Fri, 27 Jun 2025 11:08:59 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>, Samuel Holland <samuel.holland@...ive.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Russell King <linux@...linux.org.uk>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
 Gregory CLEMENT <gregory.clement@...tlin.com>, 
 Cyrille Pitchen <cyrille.pitchen@...el.com>, 
 Harini Katakam <harini.katakam@...inx.com>, 
 Rafal Ozieblo <rafalo@...ence.com>, 
 Haavard Skinnemoen <hskinnemoen@...el.com>, Jeff Garzik <jeff@...zik.org>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
 linux-mips@...r.kernel.org, Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Tawfik Bayouk <tawfik.bayouk@...ileye.com>, 
 Théo Lebrun <theo.lebrun@...tlin.com>
Subject: [PATCH net-next v2 13/18] net: macb: avoid double endianness swap
 in macb_set_hwaddr()

writel() does a CPU->LE conversion. Drop manual cpu_to_le*() calls.

On little-endian system:
 - cpu_to_le32() is a no-op (LE->LE),
 - writel() is a no-op (LE->LE),
 - dev_addr will therefore not be swapped and written as-is.

On big-endian system:
 - cpu_to_le32() is a swap (BE->LE),
 - writel() is a swap (BE->LE),
 - dev_addr will therefore be swapped twice and written as a BE value.

This was found using sparse:
   ⟩ make C=2 drivers/net/ethernet/cadence/macb_main.o
   warning: incorrect type in assignment (different base types)
      expected unsigned int [usertype] bottom
      got restricted __le32 [usertype]
   warning: incorrect type in assignment (different base types)
      expected unsigned short [usertype] top
      got restricted __le16 [usertype]
   ...

Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 578e72c7727d4f578478ff2b3d0a6316327271b1..34223dad2d01ae4bcefc0823c868a67f59435638 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -265,9 +265,9 @@ static void macb_set_hwaddr(struct macb *bp)
 	u32 bottom;
 	u16 top;

-	bottom = cpu_to_le32(*((u32 *)bp->dev->dev_addr));
+	bottom = *((u32 *)bp->dev->dev_addr);
 	macb_or_gem_writel(bp, SA1B, bottom);
-	top = cpu_to_le16(*((u16 *)(bp->dev->dev_addr + 4)));
+	top = *((u16 *)(bp->dev->dev_addr + 4));
 	macb_or_gem_writel(bp, SA1T, top);

 	if (gem_has_ptp(bp)) {

-- 
2.50.0