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net: apple: bmac: use crc32() instead of hand-rolled equivalent

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The calculation done by bmac_crc(addr) followed by taking the low 6 bits
and reversing them is equivalent to taking the high 6 bits from
crc32(~0, addr, ETH_ALEN).  Just do that instead.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://patch.msgid.link/20250513050142.635391-1-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Biggers
2025-05-12 22:01:42 -07:00
committed by Jakub Kicinski
parent 88906f5595
commit a1dc1deeac
1 changed files with 2 additions and 58 deletions
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60
drivers/net/ethernet/apple/bmac.c
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@@ -20,7 +20,6 @@
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/crc32.h>
#include <linux/crc32poly.h>
#include <linux/bitrev.h>
#include <linux/ethtool.h>
#include <linux/slab.h>
@@ -796,59 +795,6 @@ static irqreturn_t bmac_txdma_intr(int irq, void *dev_id)
}
#ifndef SUNHME_MULTICAST
/* Real fast bit-reversal algorithm, 6-bit values */
static int reverse6[64] = {
0x0,0x20,0x10,0x30,0x8,0x28,0x18,0x38,
0x4,0x24,0x14,0x34,0xc,0x2c,0x1c,0x3c,
0x2,0x22,0x12,0x32,0xa,0x2a,0x1a,0x3a,
0x6,0x26,0x16,0x36,0xe,0x2e,0x1e,0x3e,
0x1,0x21,0x11,0x31,0x9,0x29,0x19,0x39,
0x5,0x25,0x15,0x35,0xd,0x2d,0x1d,0x3d,
0x3,0x23,0x13,0x33,0xb,0x2b,0x1b,0x3b,
0x7,0x27,0x17,0x37,0xf,0x2f,0x1f,0x3f
};
static unsigned int
crc416(unsigned int curval, unsigned short nxtval)
{
unsigned int counter, cur = curval, next = nxtval;
int high_crc_set, low_data_set;
/* Swap bytes */
next = ((next & 0x00FF) << 8) | (next >> 8);
/* Compute bit-by-bit */
for (counter = 0; counter < 16; ++counter) {
/* is high CRC bit set? */
if ((cur & 0x80000000) == 0) high_crc_set = 0;
else high_crc_set = 1;
cur = cur << 1;
if ((next & 0x0001) == 0) low_data_set = 0;
else low_data_set = 1;
next = next >> 1;
/* do the XOR */
if (high_crc_set ^ low_data_set) cur = cur ^ CRC32_POLY_BE;
}
return cur;
}
static unsigned int
bmac_crc(unsigned short *address)
{
unsigned int newcrc;
XXDEBUG(("bmac_crc: addr=%#04x, %#04x, %#04x\n", *address, address[1], address[2]));
newcrc = crc416(0xffffffff, *address); /* address bits 47 - 32 */
newcrc = crc416(newcrc, address[1]); /* address bits 31 - 16 */
newcrc = crc416(newcrc, address[2]); /* address bits 15 - 0 */
return(newcrc);
}
/*
* Add requested mcast addr to BMac's hash table filter.
*
@@ -861,8 +807,7 @@ bmac_addhash(struct bmac_data *bp, unsigned char *addr)
unsigned short mask;
if (!(*addr)) return;
crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
crc = crc32(~0, addr, ETH_ALEN) >> 26;
if (bp->hash_use_count[crc]++) return; /* This bit is already set */
mask = crc % 16;
mask = (unsigned char)1 << mask;
@@ -876,8 +821,7 @@ bmac_removehash(struct bmac_data *bp, unsigned char *addr)
unsigned char mask;
/* Now, delete the address from the filter copy, as indicated */
crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
crc = crc32(~0, addr, ETH_ALEN) >> 26;
if (bp->hash_use_count[crc] == 0) return; /* That bit wasn't in use! */
if (--bp->hash_use_count[crc]) return; /* That bit is still in use */
mask = crc % 16;