[PATCH 2/2] mtd: spi-nor: spansion: Discover current address mode by CRC

[Takahiro Kuwano]

On 10/5/2022 4:10 PM, Tudor.Ambarus at microchip.com wrote:
> Hi, Takahiro,
> 
> On 8/12/22 11:06, tkuw584924 at gmail.com wrote:
>> +#define CRC32C_POLY    0x1edc6f41
>> +static u32 cypress_nor_calc_crc32c(u32 len, u8 *buf)
>> +{
>> +       u32 crc = 0;
>> +       int i;
>> +
>> +       while (len--) {
>> +               crc ^= *buf++ << 24;
>> +               for (i = 0; i < 8; i++)
>> +                       crc = (crc << 1) ^ ((crc & 0x80000000) ? CRC32C_POLY :
>> +                                           0);
>> +       }
>> +
>> +       return crc;
>> +}
> 
> I haven't gone through the details of the patch set, but I like the idea.
> I stumbled on your crc implementation. Can't we use #include <linux/crc32.h>
> instead?
> 
CRC32C BE is a missing piece in lib/crc32 so I added this local helper.

I have created following patch that adds CRC32C BE into lib/crc32.
Do you agree to submit this? 
We also need to add test case to crc32test.c.


diff --git a/include/linux/crc32.h b/include/linux/crc32.h
index 9e8a032c1788..adbfd886ccf8 100644
--- a/include/linux/crc32.h
+++ b/include/linux/crc32.h
@@ -37,6 +37,7 @@ static inline u32 crc32_le_combine(u32 crc1, u32 crc2, size_t len2)
 }
 
 u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len);
+u32 __pure __crc32c_be(u32 crc, unsigned char const *p, size_t len);
 
 /**
  * __crc32c_le_combine - Combine two crc32c check values into one. For two
diff --git a/include/linux/crc32poly.h b/include/linux/crc32poly.h
index 62c4b7790a28..ed5d81f61d4e 100644
--- a/include/linux/crc32poly.h
+++ b/include/linux/crc32poly.h
@@ -16,5 +16,6 @@
  * x^8+x^6+x^0
  */
 #define CRC32C_POLY_LE 0x82F63B78
+#define CRC32C_POLY_BE 0x1EDC6F41
 
 #endif /* _LINUX_CRC32_POLY_H */
diff --git a/lib/crc32.c b/lib/crc32.c
index 5649847d0a8d..15dc6f99ff46 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -335,10 +335,19 @@ u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len)
 {
 	return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE);
 }
+u32 __pure __weak __crc32c_be(u32 crc, unsigned char const *p, size_t len)
+{
+	return crc32_be_generic(crc, p, len, NULL, CRC32C_POLY_BE);
+}
 #else
 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len)
 {
 	return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE);
 }
+u32 __pure __weak __crc32c_be(u32 crc, unsigned char const *p, size_t len)
+{
+	return crc32_be_generic(crc, p, len, crc32ctable_be, CRC32C_POLY_BE);
+}
 #endif
 EXPORT_SYMBOL(crc32_be);
+EXPORT_SYMBOL(__crc32c_be);
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index f755b997b967..fcb90c496e48 100644
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -26,6 +26,7 @@
 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 crc32ctable_be[BE_TABLE_ROWS][256];
 
 /**
  * crc32init_le() - allocate and initialize LE table data
@@ -67,29 +68,40 @@ 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) ? CRC32_POLY_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(CRC32_POLY_BE, crc32table_be);
+}
+
+static void crc32cinit_be(void)
+{
+	crc32init_be_generic(CRC32C_POLY_BE, crc32ctable_be);
+}
+
 static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
 {
 	int i, j;
@@ -137,6 +149,15 @@ int main(int argc, char** argv)
 			     LE_TABLE_SIZE, "tole");
 		printf("};\n");
 	}
+	if (CRC_BE_BITS > 1) {
+		crc32cinit_be();
+		printf("static const u32 ____cacheline_aligned "
+		       "crc32ctable_be[%d][%d] = {",
+		       BE_TABLE_ROWS, BE_TABLE_SIZE);
+		output_table(crc32ctable_be, BE_TABLE_ROWS,
+			     BE_TABLE_SIZE, "tobe");
+		printf("};\n");
+	}
 
 	return 0;
 }