writeprotect_ranges.c: add more range functions

Not all chips follow the same pattern. There are differences in how CMP
bit is treated or in block size used.

Change-Id: Ied7b27be2ee2426af8f473432e2b01a290de2365
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/66212
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

4 files changed, 73 insertions, 12 deletions

diff --git a/include/chipdrivers.h b/include/chipdrivers.h
index 3b07afe31..34e3af8d8 100644
--- a/include/chipdrivers.h
+++ b/include/chipdrivers.h
@@ -216,5 +216,8 @@ int spi_block_erase_emulation(struct flashctx *flash, unsigned int addr, unsigne
 
 /* writeprotect_ranges.c */
 void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_64k_block(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_bit_cmp(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_2x_block(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
 
 #endif /* !__CHIPDRIVERS_H__ */
diff --git a/include/flash.h b/include/flash.h
index 23222c722..b4b56fe00 100644
--- a/include/flash.h
+++ b/include/flash.h
@@ -224,8 +224,11 @@ struct reg_bit_info {
 struct wp_bits;
 
 enum decode_range_func {
-	NO_DECODE_RANGE_FUNC = 0, /* 0 indicates no range decode funciton is set. */
+	NO_DECODE_RANGE_FUNC = 0, /* 0 indicates no range decode function is set. */
 	DECODE_RANGE_SPI25 = 1,
+	DECODE_RANGE_SPI25_64K_BLOCK = 2,
+	DECODE_RANGE_SPI25_BIT_CMP = 3,
+	DECODE_RANGE_SPI25_2X_BLOCK = 4,
 };
 typedef void (decode_range_func_t)(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
 
diff --git a/writeprotect.c b/writeprotect.c
index 1ac0c1ac4..38ac997ef 100644
--- a/writeprotect.c
+++ b/writeprotect.c
@@ -211,6 +211,9 @@ static decode_range_func_t *lookup_decode_range_func_ptr(const struct flashchip
 {
 	switch (chip->decode_range) {
 		case DECODE_RANGE_SPI25: return &decode_range_spi25;
+		case DECODE_RANGE_SPI25_64K_BLOCK: return &decode_range_spi25_64k_block;
+		case DECODE_RANGE_SPI25_BIT_CMP: return &decode_range_spi25_bit_cmp;
+		case DECODE_RANGE_SPI25_2X_BLOCK: return &decode_range_spi25_2x_block;
 	/* default: total function, 0 indicates no decode range function set. */
 		case NO_DECODE_RANGE_FUNC: return NULL;
 	};
diff --git a/writeprotect_ranges.c b/writeprotect_ranges.c
index dacce322d..45678f22a 100644
--- a/writeprotect_ranges.c
+++ b/writeprotect_ranges.c
@@ -17,11 +17,11 @@
 #include "writeprotect.h"
 #include "chipdrivers.h"
 
-/*
- * Protection range calculation that works with many common SPI flash chips.
- */
-void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+static void decode_range_generic(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len,
+				 bool fixed_block_len, bool apply_cmp_to_bp, int coeff_offset)
 {
+	const bool cmp = bits->cmp_bit_present && bits->cmp == 1;
+
 	/* Interpret BP bits as an integer */
 	size_t bp = 0;
 	size_t bp_max = 0;
@@ -31,6 +31,15 @@ void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits,
 		bp_max |= 1 << i;
 	}
 
+	/*
+	 * Most chips: the CMP bit only negates the range.
+	 *
+	 * Some MX chips: the CMP bit negates the BP bits and the range.
+	 * (CMP bit is often the MSB BP bit in such chips.)
+	 */
+	if (cmp && apply_cmp_to_bp)
+		bp ^= bp_max;
+
 	if (bp == 0) {
 		/* Special case: all BP bits are 0 => no write protection */
 		*len = 0;
@@ -40,14 +49,14 @@ void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits,
 	} else {
 		/*
 		 * Usual case: the BP bits encode a coefficient in the form
-		 * `coeff = 2 ** (bp - 1)`.
+		 * `coeff = 2 ** (bp - offset)` where `offset == 1`.
 		 *
 		 * The range's length is given by multiplying the coefficient
 		 * by a base unit, usually a 4K sector or a 64K block.
 		 */
 
-		size_t coeff     = 1 << (bp - 1);
-		size_t max_coeff = 1 << (bp_max - 2);
+		size_t coeff     = 1 << (bp - coeff_offset);
+		size_t max_coeff = 1 << (bp_max - coeff_offset - 1);
 
 		size_t sector_len        = 4  * KiB;
 		size_t default_block_len = 64 * KiB;
@@ -62,14 +71,19 @@ void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits,
 		} else {
 			/*
 			 * SEC=0 or is not present, protect blocks.
-			 *
+			 */
+			size_t block_len = default_block_len;
+
+			/*
 			 * With very large chips, the 'block' size can be
 			 * larger than 64K. This occurs when a larger block
 			 * size is needed so that half the chip can be
 			 * protected by the maximum possible coefficient.
 			 */
-			size_t min_block_len = chip_len / 2 / max_coeff;
-			size_t block_len = max(min_block_len, default_block_len);
+			if (!fixed_block_len) {
+				size_t min_block_len = chip_len / 2 / max_coeff;
+				block_len = max(min_block_len, default_block_len);
+			}
 
 			*len = min(block_len * coeff, chip_len);
 		}
@@ -79,7 +93,7 @@ void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits,
 	bool protect_top = bits->tb_bit_present ? (bits->tb == 0) : 1;
 
 	/* Apply CMP bit */
-	if (bits->cmp_bit_present && bits->cmp == 1) {
+	if (cmp) {
 		*len = chip_len - *len;
 		protect_top = !protect_top;
 	}
@@ -90,3 +104,41 @@ void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits,
 	else
 		*start = 0;
 }
+
+/*
+ * Protection range calculation that works with many common SPI flash chips.
+ */
+void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/1);
+}
+
+/*
+ * Do not adjust block size to be able to fill half of the chip.
+ */
+void decode_range_spi25_64k_block(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/true, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/1);
+}
+
+/*
+ * Inverts BP bits when CMP is set and treats all ones in BP bits as a request to protect whole chip regardless
+ * of the CMP bit.
+ */
+void decode_range_spi25_bit_cmp(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/true, /*coeff_offset=*/1);
+}
+
+/*
+ * This multiplies coefficient by 2.  To be used with chips which have more BP bits than needed, such that the
+ * most significant BP bit effectively acts as "protect whole chip" flag.
+ */
+void decode_range_spi25_2x_block(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/0);
+}