netdev - [PATCH net] net: enetc: Correct endianness handling in _enetc_rd

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Message-Id: <20250624-etnetc-le-v1-1-a73a95d96e4e@kernel.org>
Date: Tue, 24 Jun 2025 17:35:12 +0100
From: Simon Horman <horms@...nel.org>
To: Claudiu Manoil <claudiu.manoil@....com>, 
 Vladimir Oltean <vladimir.oltean@....com>, Wei Fang <wei.fang@....com>, 
 Clark Wang <xiaoning.wang@....com>
Cc: 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>, 
 Alex Marginean <alexandru.marginean@....com>, imx@...ts.linux.dev, 
 netdev@...r.kernel.org
Subject: [PATCH net] net: enetc: Correct endianness handling in
 _enetc_rd_reg64

enetc_hw.h provides two versions of _enetc_rd_reg64.
One which simply calls ioread64() when available.
And another that composes the 64-bit result from ioread32() calls.

In the second case the code appears to assume that each ioread32() call
returns a little-endian value. However both the shift and logical or
used to compose the return value would not work correctly on big endian
systems if this were the case. Moreover, this is inconsistent with the
first case where the return value of ioread64() is assumed to be in host
byte order.

It appears that the correct approach is for both versions to treat the
return value of ioread*() functions as being in host byte order. And
this patch corrects the ioread32()-based version to do so.

This is a bug but would only manifest on big endian systems
that make use of the ioread32-based implementation of _enetc_rd_reg64.
While all in-tree users of this driver are little endian and
make use of the ioread64-based implementation of _enetc_rd_reg64.
Thus, no in-tree user of this driver is affected by this bug.

Flagged by Sparse.
Compile tested only.

Cc: Wei Fang <wei.fang@....com>
Fixes: 16eb4c85c964 ("enetc: Add ethtool statistics")
Closes: https://lore.kernel.org/all/AM9PR04MB850500D3FC24FE23DEFCEA158879A@AM9PR04MB8505.eurprd04.prod.outlook.com/
Signed-off-by: Simon Horman <horms@...nel.org>
---
 drivers/net/ethernet/freescale/enetc/enetc_hw.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_hw.h b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
index 4098f01479bc..53e8d18c7a34 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_hw.h
+++ b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
@@ -507,7 +507,7 @@ static inline u64 _enetc_rd_reg64(void __iomem *reg)
 		tmp = ioread32(reg + 4);
 	} while (high != tmp);

-	return le64_to_cpu((__le64)high << 32 | low);
+	return (u64)high << 32 | low;
 }
 #endif