[PATCH 1/3] mtd: spi-nor: reimplement block protection handling

Jungseung Lee
2020-03-04T11:08:57Z

The current mainline locking was restricted and could only be applied
to flashes that has 3 block protection bit and fixed locking ratio.

A new method of normalization was reached at the end of the discussion [1].

(1) - if bp slot is insufficient.
(2) - if bp slot is sufficient.

if (bp_slots_needed > bp_slots) // (1)
min_prot_length = sector_size << (bp_slots_needed - bp_slots);
else // (2)
min_prot_length = sector_size;

This patch changes block protection handling logic based on min_prot_length.
It is suitable for the overall flashes with exception of some corner case
and easy to extend and apply for the case of 2bit or 4bit block protection.

[1] http://lists.infradead.org/pipermail/linux-mtd/2020-February/093934.html

Signed-off-by: Jungseung Lee <js07.lee@samsung.com>
---
drivers/mtd/spi-nor/spi-nor.c | 110 ++++++++++++++++++++--------------
1 file changed, 66 insertions(+), 44 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index caf0c109cca0..c58c27552a74 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1784,29 +1784,64 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
return ret;
}

+static u8 spi_nor_get_bp_mask(struct spi_nor *nor)
+{
+ return SR_BP2 | SR_BP1 | SR_BP0;
+}
+
+static u8 spi_nor_get_tb_mask(struct spi_nor *nor)
+{
+ if (nor->flags & SNOR_F_HAS_SR_TB_BIT6)
+ return SR_TB_BIT6;
+ else
+ return SR_TB_BIT5;
+}
+
+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;
+
+ /* Reserved one for "protect none" and one for "protect all". */
+ bp_slots = bp_slots - 2;
+
+ bp_slots_needed = ilog2(nor->info->n_sectors);
+
+ if (bp_slots_needed > bp_slots)
+ return nor->info->sector_size <<
+ (bp_slots_needed - bp_slots);
+ else
+ return nor->info->sector_size;
+}
+
static void stm_get_locked_range(struct spi_nor *nor, u8 sr, loff_t *ofs,
uint64_t *len)
{
struct mtd_info *mtd = &nor->mtd;
- u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
- u8 tb_mask = SR_TB_BIT5;
- int pow;
+ 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;

- if (nor->flags & SNOR_F_HAS_SR_TB_BIT6)
- tb_mask = SR_TB_BIT6;
-
- if (!(sr & mask)) {
+ if (!bp) {
/* No protection */
*ofs = 0;
*len = 0;
- } else {
- pow = ((sr & mask) ^ mask) >> SR_BP_SHIFT;
- *len = mtd->size >> pow;
- if (nor->flags & SNOR_F_HAS_SR_TB && sr & tb_mask)
- *ofs = 0;
- else
- *ofs = mtd->size - *len;
+ return;
}
+
+ min_prot_len = stm_get_min_prot_length(nor);
+ *len = min_prot_len << (bp - 1);
+
+ if (*len > mtd->size)
+ *len = mtd->size;
+
+ if (nor->flags & SNOR_F_HAS_SR_TB && sr & tb_mask)
+ *ofs = 0;
+ else
+ *ofs = mtd->size - *len;
}

/*
@@ -1880,8 +1915,9 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
struct mtd_info *mtd = &nor->mtd;
int ret, status_old, status_new;
- u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
- u8 tb_mask = SR_TB_BIT5;
+ int min_prot_len;
+ u8 mask = spi_nor_get_bp_mask(nor);
+ u8 tb_mask = spi_nor_get_tb_mask(nor);
u8 pow, val;
loff_t lock_len;
bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
@@ -1918,20 +1954,14 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
else
lock_len = ofs + len;

- if (nor->flags & SNOR_F_HAS_SR_TB_BIT6)
- tb_mask = SR_TB_BIT6;
+ if (lock_len == mtd->size) {
+ val = mask; /* fully locked */
+ } else {
+ min_prot_len = stm_get_min_prot_length(nor);
+ pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
+ val = pow << SR_BP_SHIFT;
+ }

- /*
- * Need smallest pow such that:
- *
- * 1 / (2^pow) <= (len / size)
- *
- * so (assuming power-of-2 size) we do:
- *
- * pow = ceil(log2(size / len)) = log2(size) - floor(log2(len))
- */
- pow = ilog2(mtd->size) - ilog2(lock_len);
- val = mask - (pow << SR_BP_SHIFT);
if (val & ~mask)
return -EINVAL;
/* Don't "lock" with no region! */
@@ -1966,8 +1996,9 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
struct mtd_info *mtd = &nor->mtd;
int ret, status_old, status_new;
- u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
- u8 tb_mask = SR_TB_BIT5;
+ int min_prot_len;
+ u8 mask = spi_nor_get_bp_mask(nor);
+ u8 tb_mask = spi_nor_get_tb_mask(nor);
u8 pow, val;
loff_t lock_len;
bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
@@ -2004,22 +2035,13 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
else
lock_len = ofs;

- if (nor->flags & SNOR_F_HAS_SR_TB_BIT6)
- tb_mask = SR_TB_BIT6;
- /*
- * Need largest pow such that:
- *
- * 1 / (2^pow) >= (len / size)
- *
- * so (assuming power-of-2 size) we do:
- *
- * pow = floor(log2(size / len)) = log2(size) - ceil(log2(len))
- */
- pow = ilog2(mtd->size) - order_base_2(lock_len);
if (lock_len == 0) {
val = 0; /* fully unlocked */
} else {
- val = mask - (pow << SR_BP_SHIFT);
+ min_prot_len = stm_get_min_prot_length(nor);
+ pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
+ val = pow << SR_BP_SHIFT;
+
/* Some power-of-two sizes are not supported */
if (val & ~mask)
return -EINVAL;
--
2.17.1