[PATCH 2/3] mtd: spi-nor: add 4bit block protection support

[Jungseung Lee <js07.lee@xxxxxxxxxxx>]

Currently, we are supporting block protection only for
flash chips with 3 block protection bits in the SR register.
This patch enables block protection support for flashes with
4 block protection bits(bp0-3).

Signed-off-by: Jungseung Lee <js07.lee@xxxxxxxxxxx>
---
 drivers/mtd/spi-nor/spi-nor.c | 82 ++++++++++++++++++++++++++++++++---
 include/linux/mtd/spi-nor.h   |  4 ++
 2 files changed, 79 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index c58c27552a74..31a2106e529a 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -238,6 +238,14 @@ struct flash_info {
 					 * status register. Must be used with
 					 * SPI_NOR_HAS_TB.
 					 */
+#define SPI_NOR_4BIT_BP		BIT(17)	/*
+					 * Flash SR has 4 bit fields (BP0-3)
+					 * for block protection.
+					 */
+#define SPI_NOR_BP3_SR_BIT6	BIT(18)	/*
+					 * BP3 is bit 6 of status register.
+					 * Must be used with SPI_NOR_4BIT_BP.
+					 */
 
 	/* Part specific fixup hooks. */
 	const struct spi_nor_fixups *fixups;
@@ -1786,7 +1794,16 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 
 static u8 spi_nor_get_bp_mask(struct spi_nor *nor)
 {
-	return SR_BP2 | SR_BP1 | SR_BP0;
+	u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
+
+	if (nor->flags & SNOR_F_HAS_4BIT_BP) {
+		if (nor->flags & SNOR_F_HAS_SR_BP3_BIT6)
+			mask = mask | SR_BP3_BIT6;
+		else
+			mask = mask | SR_BP3_BIT5;
+	}
+
+	return mask;
 }
 
 static u8 spi_nor_get_tb_mask(struct spi_nor *nor)
@@ -1797,12 +1814,26 @@ static u8 spi_nor_get_tb_mask(struct spi_nor *nor)
 		return SR_TB_BIT5;
 }
 
+static u8 stm_get_bpval_from_sr(struct spi_nor *nor, u8 sr) {
+	u8 mask = spi_nor_get_bp_mask(nor);
+	u8 bp = sr & mask;
+
+	if (bp & SR_BP3_BIT6)
+		bp = (bp & ~BIT(6)) | BIT(5);
+
+	bp = bp >> SR_BP_SHIFT;
+
+	return bp;
+}
+
 static int stm_get_min_prot_length(struct spi_nor *nor)
 {
 	int bp_slots, bp_slots_needed;
-	u8 mask = spi_nor_get_bp_mask(nor);
 
-	bp_slots = (mask >> SR_BP_SHIFT) + 1;
+	if (nor->flags & SNOR_F_HAS_4BIT_BP)
+		bp_slots = 1 << 4;
+	else
+		bp_slots = 1 << 3;
 
 	/* Reserved one for "protect none" and one for "protect all". */
 	bp_slots = bp_slots - 2;
@@ -1821,9 +1852,8 @@ static void stm_get_locked_range(struct spi_nor *nor, u8 sr, loff_t *ofs,
 {
 	struct mtd_info *mtd = &nor->mtd;
 	int min_prot_len;
-	u8 mask = spi_nor_get_bp_mask(nor);
 	u8 tb_mask = spi_nor_get_tb_mask(nor);
-	u8 bp = (sr & mask) >> SR_BP_SHIFT;
+	u8 bp = stm_get_bpval_from_sr(nor, sr);
 
 	if (!bp) {
 		/* No protection */
@@ -1881,7 +1911,7 @@ static int stm_is_unlocked_sr(struct spi_nor *nor, loff_t ofs, uint64_t len,
 
 /*
  * Lock a region of the flash. Compatible with ST Micro and similar flash.
- * Supports the block protection bits BP{0,1,2} in the status register
+ * Supports the block protection bits BP{0,1,2}/BP{0,1,2,3} in the status register
  * (SR). Does not support these features found in newer SR bitfields:
  *   - SEC: sector/block protect - only handle SEC=0 (block protect)
  *   - CMP: complement protect - only support CMP=0 (range is not complemented)
@@ -1889,7 +1919,7 @@ static int stm_is_unlocked_sr(struct spi_nor *nor, loff_t ofs, uint64_t len,
  * Support for the following is provided conditionally for some flash:
  *   - TB: top/bottom protect
  *
- * Sample table portion for 8MB flash (Winbond w25q64fw):
+ * Sample table portion for 8MB flash (Winbond w25q64fw / BP0-2):
  *
  *   SEC  |  TB   |  BP2  |  BP1  |  BP0  |  Prot Length  | Protected Portion
  *  --------------------------------------------------------------------------
@@ -1909,6 +1939,32 @@ static int stm_is_unlocked_sr(struct spi_nor *nor, loff_t ofs, uint64_t len,
  *    0   |   1   |   1   |   0   |   1   |  2 MB         | Lower 1/4
  *    0   |   1   |   1   |   1   |   0   |  4 MB         | Lower 1/2
  *
+ * Sample table portion for 64MB flash (Micron n25q512ax3 / BP0-3):
+ *
+ *   TB   |  BP3  |  BP2  |  BP1  |  BP0  |  Prot Length  | Protected Portion
+ *  --------------------------------------------------------------------------
+ *    0   |   0   |   0   |   0   |   0   |  NONE         | NONE
+ *    0   |   0   |   0   |   0   |   1   |   64 KB       | Upper 1/1024
+ *    0   |   0   |   0   |   1   |   0   |  128 KB       | Upper 1/512
+ *    0   |   0   |   0   |   1   |   1   |  256 KB       | Upper 1/256
+ *   ...
+ *    0   |   1   |   0   |   0   |   1   |  16 MB        | Upper 1/4
+ *    0   |   1   |   0   |   1   |   0   |  32 MB        | Upper 1/2
+ *    0   |   1   |   0   |   1   |   1   |  64 MB        | ALL
+ *    0   |   1   |   1   |   0   |   0   |  64 MB        | ALL
+ *   ...
+ *  ------|-------|-------|-------|-------|---------------|-------------------
+ *    1   |   0   |   0   |   0   |   0   |   NONE        | NONE
+ *    1   |   0   |   0   |   0   |   1   |   64 KB       | Lower 1/1024
+ *    1   |   0   |   0   |   1   |   0   |  128 KB       | Lower 1/512
+ *    1   |   0   |   0   |   1   |   1   |  256 KB       | Lower 1/256
+ *   ...
+ *    1   |   1   |   0   |   0   |   1   |  16 MB        | Lower 1/4
+ *    1   |   1   |   0   |   1   |   0   |  32 MB        | Lower 1/2
+ *    1   |   1   |   0   |   1   |   1   |  64 MB        | ALL
+ *    1   |   1   |   1   |   0   |   0   |  64 MB        | ALL
+ *   ...
+ *
  * Returns negative on errors, 0 on success.
  */
 static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
@@ -1960,6 +2016,9 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 		min_prot_len = stm_get_min_prot_length(nor);
 		pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
 		val = pow << SR_BP_SHIFT;
+
+		if (val & BIT(5) && mask & SR_BP3_BIT6)
+			val = (val & ~BIT(5)) | BIT(6);
 	}
 
 	if (val & ~mask)
@@ -2042,6 +2101,9 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 		pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
 		val = pow << SR_BP_SHIFT;
 
+		if (val & BIT(5) && mask & SR_BP3_BIT6)
+			val = (val & ~BIT(5)) | BIT(6);
+
 		/* Some power-of-two sizes are not supported */
 		if (val & ~mask)
 			return -EINVAL;
@@ -5244,6 +5306,12 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 	if (info->flags & USE_CLSR)
 		nor->flags |= SNOR_F_USE_CLSR;
 
+	if (info->flags & SPI_NOR_4BIT_BP) {
+		nor->flags |= SNOR_F_HAS_4BIT_BP;
+		if (info->flags & SPI_NOR_BP3_SR_BIT6)
+			nor->flags |= SNOR_F_HAS_SR_BP3_BIT6;
+	}
+
 	if (info->flags & SPI_NOR_NO_ERASE)
 		mtd->flags |= MTD_NO_ERASE;
 
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index de90724f62f1..0190ed21576a 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -129,7 +129,9 @@
 #define SR_BP1			BIT(3)	/* Block protect 1 */
 #define SR_BP2			BIT(4)	/* Block protect 2 */
 #define SR_TB_BIT5		BIT(5)	/* Top/Bottom protect */
+#define SR_BP3_BIT5		BIT(5)	/* Block protect 3 */
 #define SR_TB_BIT6		BIT(6)	/* Top/Bottom protect */
+#define SR_BP3_BIT6		BIT(6)	/* Block protect 3 */
 #define SR_SRWD			BIT(7)	/* SR write protect */
 /* Spansion/Cypress specific status bits */
 #define SR_E_ERR		BIT(5)
@@ -240,6 +242,8 @@ enum spi_nor_option_flags {
 	SNOR_F_HAS_16BIT_SR	= BIT(9),
 	SNOR_F_NO_READ_CR	= BIT(10),
 	SNOR_F_HAS_SR_TB_BIT6	= BIT(11),
+	SNOR_F_HAS_4BIT_BP	= BIT(12),
+	SNOR_F_HAS_SR_BP3_BIT6	= BIT(13),
 
 };
 
-- 
2.17.1


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