mtd: spi-nor: refactor block protection functions
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Fri Nov 6 10:59:23 PST 2015
Gitweb: http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=62593cf40b23b523b9fc9334ca61ba6c595ebb09
Commit: 62593cf40b23b523b9fc9334ca61ba6c595ebb09
Parent: f8900258906c3533b91e779e80f75ec80de816c0
Author: Brian Norris <computersforpeace at gmail.com>
AuthorDate: Tue Sep 1 12:57:11 2015 -0700
Committer: Brian Norris <computersforpeace at gmail.com>
CommitDate: Tue Oct 13 18:22:54 2015 -0700
mtd: spi-nor: refactor block protection functions
This code was a bit sloppy, would produce a lot of copy-and-paste, and
did not always provide a sensible interface:
* It didn't validate the length for LOCK and the offset for UNLOCK, so
we were essentially discarding half of the user-supplied data and
assuming what they wanted to lock/unlock
* It didn't do very good error checking
* It didn't make use of the fact that this operation works on
power-of-two dimensions
So, rewrite this to do proper bit arithmetic rather than a bunch of
hard-coded condition tables. Now we have:
* More comments on how this was derived
* Notes on what is (and isn't) supported
* A more exendible function, so we could add support for other
protection ranges
* More accurate locking - e.g., suppose the top quadrant is locked (75%
to 100%); then in the following cases, case (a) will succeed but (b)
will not (return -EINVAL):
(a) user requests lock 3rd quadrant (50% to 75%)
(b) user requests lock 3rd quadrant, minus a few blocks (e.g., 50%
to 73%)
Case (b) *should* fail, since we'd have to lock blocks that weren't
requested. But the old implementation didn't know the difference and
would lock the entire second half (50% to 100%)
This refactoring work will also help enable the addition of
mtd_is_locked() support and potentially the support of bottom boot
protection (TB=1).
Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
drivers/mtd/spi-nor/spi-nor.c | 171 +++++++++++++++++++++++++++++++-----------
1 file changed, 126 insertions(+), 45 deletions(-)
diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index d356a1f..3db0f2b 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -400,72 +400,153 @@ erase_err:
return ret;
}
+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;
+ int shift = ffs(mask) - 1;
+ int pow;
+
+ if (!(sr & mask)) {
+ /* No protection */
+ *ofs = 0;
+ *len = 0;
+ } else {
+ pow = ((sr & mask) ^ mask) >> shift;
+ *len = mtd->size >> pow;
+ *ofs = mtd->size - *len;
+ }
+}
+
+/*
+ * Return 1 if the entire region is locked, 0 otherwise
+ */
+static int stm_is_locked_sr(struct spi_nor *nor, loff_t ofs, uint64_t len,
+ u8 sr)
+{
+ loff_t lock_offs;
+ uint64_t lock_len;
+
+ stm_get_locked_range(nor, sr, &lock_offs, &lock_len);
+
+ return (ofs + len <= lock_offs + lock_len) && (ofs >= lock_offs);
+}
+
+/*
+ * Lock a region of the flash. Compatible with ST Micro and similar flash.
+ * Supports only the block protection bits BP{0,1,2} in the status register
+ * (SR). Does not support these features found in newer SR bitfields:
+ * - TB: top/bottom protect - only handle TB=0 (top protect)
+ * - SEC: sector/block protect - only handle SEC=0 (block protect)
+ * - CMP: complement protect - only support CMP=0 (range is not complemented)
+ *
+ * Sample table portion for 8MB flash (Winbond w25q64fw):
+ *
+ * SEC | TB | BP2 | BP1 | BP0 | Prot Length | Protected Portion
+ * --------------------------------------------------------------------------
+ * X | X | 0 | 0 | 0 | NONE | NONE
+ * 0 | 0 | 0 | 0 | 1 | 128 KB | Upper 1/64
+ * 0 | 0 | 0 | 1 | 0 | 256 KB | Upper 1/32
+ * 0 | 0 | 0 | 1 | 1 | 512 KB | Upper 1/16
+ * 0 | 0 | 1 | 0 | 0 | 1 MB | Upper 1/8
+ * 0 | 0 | 1 | 0 | 1 | 2 MB | Upper 1/4
+ * 0 | 0 | 1 | 1 | 0 | 4 MB | Upper 1/2
+ * X | X | 1 | 1 | 1 | 8 MB | ALL
+ *
+ * Returns negative on errors, 0 on success.
+ */
static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
struct mtd_info *mtd = &nor->mtd;
- uint32_t offset = ofs;
- uint8_t status_old, status_new;
- int ret = 0;
+ u8 status_old, status_new;
+ u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
+ u8 shift = ffs(mask) - 1, pow, val;
status_old = read_sr(nor);
- if (offset < mtd->size - (mtd->size / 2))
- status_new = status_old | SR_BP2 | SR_BP1 | SR_BP0;
- else if (offset < mtd->size - (mtd->size / 4))
- status_new = (status_old & ~SR_BP0) | SR_BP2 | SR_BP1;
- else if (offset < mtd->size - (mtd->size / 8))
- status_new = (status_old & ~SR_BP1) | SR_BP2 | SR_BP0;
- else if (offset < mtd->size - (mtd->size / 16))
- status_new = (status_old & ~(SR_BP0 | SR_BP1)) | SR_BP2;
- else if (offset < mtd->size - (mtd->size / 32))
- status_new = (status_old & ~SR_BP2) | SR_BP1 | SR_BP0;
- else if (offset < mtd->size - (mtd->size / 64))
- status_new = (status_old & ~(SR_BP2 | SR_BP0)) | SR_BP1;
- else
- status_new = (status_old & ~(SR_BP2 | SR_BP1)) | SR_BP0;
+ /* SPI NOR always locks to the end */
+ if (ofs + len != mtd->size) {
+ /* Does combined region extend to end? */
+ if (!stm_is_locked_sr(nor, ofs + len, mtd->size - ofs - len,
+ status_old))
+ return -EINVAL;
+ len = mtd->size - ofs;
+ }
+
+ /*
+ * 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(len);
+ val = mask - (pow << shift);
+ if (val & ~mask)
+ return -EINVAL;
+ /* Don't "lock" with no region! */
+ if (!(val & mask))
+ return -EINVAL;
+
+ status_new = (status_old & ~mask) | val;
/* Only modify protection if it will not unlock other areas */
- if ((status_new & (SR_BP2 | SR_BP1 | SR_BP0)) >
- (status_old & (SR_BP2 | SR_BP1 | SR_BP0))) {
- write_enable(nor);
- ret = write_sr(nor, status_new);
- }
+ if ((status_new & mask) <= (status_old & mask))
+ return -EINVAL;
- return ret;
+ write_enable(nor);
+ return write_sr(nor, status_new);
}
+/*
+ * Unlock a region of the flash. See stm_lock() for more info
+ *
+ * Returns negative on errors, 0 on success.
+ */
static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
{
struct mtd_info *mtd = &nor->mtd;
- uint32_t offset = ofs;
uint8_t status_old, status_new;
- int ret = 0;
+ u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
+ u8 shift = ffs(mask) - 1, pow, val;
status_old = read_sr(nor);
- if (offset+len > mtd->size - (mtd->size / 64))
- status_new = status_old & ~(SR_BP2 | SR_BP1 | SR_BP0);
- else if (offset+len > mtd->size - (mtd->size / 32))
- status_new = (status_old & ~(SR_BP2 | SR_BP1)) | SR_BP0;
- else if (offset+len > mtd->size - (mtd->size / 16))
- status_new = (status_old & ~(SR_BP2 | SR_BP0)) | SR_BP1;
- else if (offset+len > mtd->size - (mtd->size / 8))
- status_new = (status_old & ~SR_BP2) | SR_BP1 | SR_BP0;
- else if (offset+len > mtd->size - (mtd->size / 4))
- status_new = (status_old & ~(SR_BP0 | SR_BP1)) | SR_BP2;
- else if (offset+len > mtd->size - (mtd->size / 2))
- status_new = (status_old & ~SR_BP1) | SR_BP2 | SR_BP0;
- else
- status_new = (status_old & ~SR_BP0) | SR_BP2 | SR_BP1;
+ /* Cannot unlock; would unlock larger region than requested */
+ if (stm_is_locked_sr(nor, status_old, ofs - mtd->erasesize,
+ mtd->erasesize))
+ return -EINVAL;
- /* Only modify protection if it will not lock other areas */
- if ((status_new & (SR_BP2 | SR_BP1 | SR_BP0)) <
- (status_old & (SR_BP2 | SR_BP1 | SR_BP0))) {
- write_enable(nor);
- ret = write_sr(nor, status_new);
+ /*
+ * 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(mtd->size - (ofs + len));
+ if (ofs + len == mtd->size) {
+ val = 0; /* fully unlocked */
+ } else {
+ val = mask - (pow << shift);
+ /* Some power-of-two sizes are not supported */
+ if (val & ~mask)
+ return -EINVAL;
}
- return ret;
+ status_new = (status_old & ~mask) | val;
+
+ /* Only modify protection if it will not lock other areas */
+ if ((status_new & mask) >= (status_old & mask))
+ return -EINVAL;
+
+ write_enable(nor);
+ return write_sr(nor, status_new);
}
static int spi_nor_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
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