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Date: Wed, 11 Dec 2013 17:49:22 +0100
From: Frank Haverkamp <haver@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: arnd@...db.de, gregkh@...uxfoundation.org, cody@...ux.vnet.ibm.com,
schwidefsky@...ibm.com, utz.bacher@...ibm.com, mmarek@...e.cz,
rmallon@...il.com, jsvogt@...ibm.com, MIJUNG@...ibm.com,
cascardo@...ux.vnet.ibm.com, michael@...ra.de,
haver@...ux.vnet.ibm.com
Subject: [RFC 1/2] CRC32 Add GenWQE CRC to kernel CRC code
Our GenWQE driver is using a CRC32 polynom, which as far as I could
see, no one else is using in the kernel. In its original version we
implemented our own CRC32, but I think it is nicer to use the common
code as suggested by Greg.
I did not want to add yet another crc32g_table and waste (1KiB) memory
when no one else is using it. I tried to externalize the
crc32init_be_generic and crc32_be_generic functions. I failed. The
crc32init* I found is used to autogenerate code can is itself not part
of the resulting kernel.
As result I gave up on that approach and just added the GenWQE special
polynom in addition to the other 3 crc tables. I wanted to figure out
if it is possible in principle to use the generic code.
Is the consumption of 1KiB for a little table justifyable if it
currently has just one user?
Signed-off-by: Frank Haverkamp <haver@...ux.vnet.ibm.com>
---
include/linux/crc32.h | 2 2 + 0 - 0 !
lib/crc32.c | 10 10 + 0 - 0 !
lib/crc32defs.h | 5 5 + 0 - 0 !
lib/gen_crc32table.c | 39 31 + 8 - 0 !
4 files changed, 48 insertions(+), 8 deletions(-)
--- a/include/linux/crc32.h
+++ b/include/linux/crc32.h
@@ -11,6 +11,8 @@
extern u32 crc32_le(u32 crc, unsigned char const *p, size_t len);
extern u32 crc32_be(u32 crc, unsigned char const *p, size_t len);
+extern u32 __crc32g_be(u32 crc, unsigned char const *p, size_t len);
+
/**
* crc32_le_combine - Combine two crc32 check values into one. For two
* sequences of bytes, seq1 and seq2 with lengths len1
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -339,14 +339,24 @@ u32 __pure crc32_be(u32 crc, unsigned ch
{
return crc32_be_generic(crc, p, len, NULL, CRCPOLY_BE);
}
+u32 __pure __crc32g_be(u32 crc, unsigned char const *p, size_t len)
+{
+ return crc32_be_generic(crc, p, len, NULL, CRC32G_POLY_BE);
+}
#else
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
return crc32_be_generic(crc, p, len,
(const u32 (*)[256])crc32table_be, CRCPOLY_BE);
}
+u32 __pure __crc32g_be(u32 crc, unsigned char const *p, size_t len)
+{
+ return crc32_be_generic(crc, p, len,
+ (const u32 (*)[256])crc32gtable_be, CRC32G_POLY_BE);
+}
#endif
EXPORT_SYMBOL(crc32_be);
+EXPORT_SYMBOL(__crc32g_be);
#ifdef CONFIG_CRC32_SELFTEST
--- a/lib/crc32defs.h
+++ b/lib/crc32defs.h
@@ -13,6 +13,11 @@
*/
#define CRC32C_POLY_LE 0x82F63B78
+/*
+ * This is the CRC32g polynomial, used by the GenWQE driver.
+ */
+#define CRC32G_POLY_BE 0x20044009
+
/* Try to choose an implementation variant via Kconfig */
#ifdef CONFIG_CRC32_SLICEBY8
# define CRC_LE_BITS 64
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -24,6 +24,7 @@
static uint32_t crc32table_le[LE_TABLE_ROWS][256];
static uint32_t crc32table_be[BE_TABLE_ROWS][256];
static uint32_t crc32ctable_le[LE_TABLE_ROWS][256];
+static uint32_t crc32gtable_be[BE_TABLE_ROWS][256];
/**
* crc32init_le() - allocate and initialize LE table data
@@ -65,29 +66,40 @@ static void crc32cinit_le(void)
}
/**
- * crc32init_be() - allocate and initialize BE table data
+ * crc32init_be_generic() - allocate and initialize BE table data
*/
-static void crc32init_be(void)
+static void crc32init_be_generic(const uint32_t polynomial,
+ uint32_t (*tab)[256])
{
unsigned i, j;
uint32_t crc = 0x80000000;
- crc32table_be[0][0] = 0;
+ tab[0][0] = 0;
for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
- crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
+ crc = (crc << 1) ^ ((crc & 0x80000000) ? polynomial : 0);
for (j = 0; j < i; j++)
- crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
+ tab[0][i + j] = crc ^ tab[0][j];
}
for (i = 0; i < BE_TABLE_SIZE; i++) {
- crc = crc32table_be[0][i];
+ crc = tab[0][i];
for (j = 1; j < BE_TABLE_ROWS; j++) {
- crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
- crc32table_be[j][i] = crc;
+ crc = tab[0][(crc >> 24) & 0xff] ^ (crc << 8);
+ tab[j][i] = crc;
}
}
}
+static void crc32init_be(void)
+{
+ crc32init_be_generic(CRCPOLY_BE, crc32table_be);
+}
+
+static void crc32ginit_be(void)
+{
+ crc32init_be_generic(CRC32G_POLY_BE, crc32gtable_be);
+}
+
static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
{
int i, j;
@@ -126,6 +138,7 @@ int main(int argc, char** argv)
BE_TABLE_SIZE, "tobe");
printf("};\n");
}
+
if (CRC_LE_BITS > 1) {
crc32cinit_le();
printf("static u32 __cacheline_aligned "
@@ -136,5 +149,15 @@ int main(int argc, char** argv)
printf("};\n");
}
+ if (CRC_BE_BITS > 1) {
+ crc32ginit_be();
+ printf("static u32 __cacheline_aligned "
+ "crc32gtable_be[%d][%d] = {",
+ BE_TABLE_ROWS, BE_TABLE_SIZE);
+ output_table(crc32gtable_be, LE_TABLE_ROWS,
+ BE_TABLE_SIZE, "tobe");
+ printf("};\n");
+ }
+
return 0;
}
--
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