diff options
| author | Nikolay Borisov <nik.borisov@suse.com> | 2025-11-24 16:25:17 +0200 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2025-11-24 17:00:37 +0100 |
| commit | 69acbdbbefbda7b7b32faa706a8f68c399c9e47b (patch) | |
| tree | 3b4d570a2f8504f128d1ad4cff94be2541a51504 | |
| parent | 187d1b27a1e436822c31e43aa58505f6dd8987e2 (diff) | |
RAS/AMD/ATL: Replace bitwise_xor_bits() with hweight16()
Doing hweight16() and checking whether the lsb is set is functionally
equivalent to what bitwise_xor_bits() does. In addition, it results in better
generated code as before gcc would inline the function 4 times. With hweight16(),
the resulting code boils down to 2 instructions - POPCNT and AND, and all
relevant CPUs support POPCNT.
An alternative would have been to use the __builtin_parity() function provided
by both Clang/GCC, however under some circumstances the compiler can choose not
to inline it but generate a library call which is unsupported in the kernel.
No functional changes.
[ bp: Massage commit message. ]
Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20251124142517.1708451-1-nik.borisov@suse.com
| -rw-r--r-- | drivers/ras/amd/atl/umc.c | 21 |
1 files changed, 5 insertions, 16 deletions
diff --git a/drivers/ras/amd/atl/umc.c b/drivers/ras/amd/atl/umc.c index 18ce419236a5..befc616d5e8a 100644 --- a/drivers/ras/amd/atl/umc.c +++ b/drivers/ras/amd/atl/umc.c @@ -49,17 +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; @@ -250,17 +239,17 @@ 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 = hweight16(col & addr_hash.bank[i].col_xor) & 1; + temp ^= hweight16(row & addr_hash.bank[i].row_xor) & 1; 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 = hweight16(col & addr_hash.pc.col_xor) & 1; + temp ^= hweight16(row & addr_hash.pc.row_xor) & 1; /* 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 ^= hweight16((bank | sid << NUM_BANK_BITS) & addr_hash.bank_xor) & 1; pc ^= temp; } |