linux-kernel - [PATCH] RAS/AMD/ATL: Remove bitwise_xor

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Message-ID: <20251113111125.823960-1-nik.borisov@suse.com>
Date: Thu, 13 Nov 2025 13:11:25 +0200
From: Nikolay Borisov <nik.borisov@...e.com>
To: Yazen.Ghannam@....com
Cc: bp@...en8.de,
	linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Nikolay Borisov <nik.borisov@...e.com>
Subject: [PATCH] RAS/AMD/ATL: Remove bitwise_xor_bits

The name of the function is somewhat misleading, it's not just XORing
bits, but is calculating the parity of the passed in value. There's
already a compiler builtin function for this - __builtin_parity. Just
use it. No functional changes.

Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>
---
 drivers/ras/amd/atl/umc.c | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/drivers/ras/amd/atl/umc.c b/drivers/ras/amd/atl/umc.c
index 6e072b7667e9..7ff4a5a1c5da 100644
--- a/drivers/ras/amd/atl/umc.c
+++ b/drivers/ras/amd/atl/umc.c
@@ -49,18 +49,6 @@ static u8 get_coh_st_inst_id_mi300(struct atl_err *err)
 	return i;
 }
 
-/* XOR the bits in @val. */
-static u16 bitwise_xor_bits(u16 val)
-{
-	u16 tmp = 0;
-	u8 i;
-
-	for (i = 0; i < 16; i++)
-		tmp ^= (val >> i) & 0x1;
-
-	return tmp;
-}
-
 struct xor_bits {
 	bool	xor_enable;
 	u16	col_xor;
@@ -250,17 +238,17 @@ static unsigned long convert_dram_to_norm_addr_mi300(unsigned long addr)
 		if (!addr_hash.bank[i].xor_enable)
 			continue;
 
-		temp  = bitwise_xor_bits(col & addr_hash.bank[i].col_xor);
-		temp ^= bitwise_xor_bits(row & addr_hash.bank[i].row_xor);
+		temp  = (u16)__builtin_parity(col & addr_hash.bank[i].col_xor);
+		temp ^= (u16)__builtin_parity(row & addr_hash.bank[i].row_xor);
 		bank ^= temp << i;
 	}
 
 	/* Calculate hash for PC bit. */
 	if (addr_hash.pc.xor_enable) {
-		temp  = bitwise_xor_bits(col  & addr_hash.pc.col_xor);
-		temp ^= bitwise_xor_bits(row  & addr_hash.pc.row_xor);
+		temp  = (u16)__builtin_parity(col & addr_hash.pc.col_xor);
+		temp ^= (u16)__builtin_parity(row & addr_hash.pc.row_xor);
 		/* Bits SID[1:0] act as Bank[5:4] for PC hash, so apply them here. */
-		temp ^= bitwise_xor_bits((bank | sid << NUM_BANK_BITS) & addr_hash.bank_xor);
+		temp ^= (u16)__builtin_parity((bank | sid << NUM_BANK_BITS) & addr_hash.bank_xor);
 		pc   ^= temp;
 	}
 
-- 
2.51.1