Commit 2695b3c7 authored by Eric Biggers's avatar Eric Biggers Committed by Thomas Bogendoerfer
Browse files

MIPS: bcm63xx: nvram: avoid inefficient use of crc32_le_combine() 



bcm963xx_nvram_checksum() was using crc32_le_combine() to update a CRC
with four zero bytes.  However, this is about 5x slower than just
CRC'ing four zero bytes in the normal way.  Just do that instead.

(We could instead make crc32_le_combine() faster on short lengths.  But
all its callers do just fine without it, so I'd like to just remove it.)

Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
parent 3590692a

include/linux/bcm963xx_nvram.h

+6 −10
Original line number Diff line number Diff line
@@ -81,25 +81,21 @@ static int __maybe_unused bcm963xx_nvram_checksum( 
	const struct bcm963xx_nvram *nvram,

	u32 *expected_out, u32 *actual_out)

{

	const u32 zero = 0;

	u32 expected, actual;

	size_t len;



	if (nvram->version <= 4) {

		expected = nvram->checksum_v4;

		len = BCM963XX_NVRAM_V4_SIZE - sizeof(u32);

		len = BCM963XX_NVRAM_V4_SIZE;

	} else {

		expected = nvram->checksum_v5;

		len = BCM963XX_NVRAM_V5_SIZE - sizeof(u32);

		len = BCM963XX_NVRAM_V5_SIZE;

	}



	/*

	 * Calculate the CRC32 value for the nvram with a checksum value

	 * of 0 without modifying or copying the nvram by combining:

	 * - The CRC32 of the nvram without the checksum value

	 * - The CRC32 of a zero checksum value (which is also 0)

	 */

	actual = crc32_le_combine(

		crc32_le(~0, (u8 *)nvram, len), 0, sizeof(u32));

	/* Calculate the CRC32 of the nvram with the checksum field set to 0. */

	actual = crc32_le(~0, nvram, len - sizeof(u32));

	actual = crc32_le(actual, &zero, sizeof(u32));



	if (expected_out)

		*expected_out = expected;