From: Michael Walle <michael@walle.cc>
To: Tudor.Ambarus@microchip.com
Cc: linux-mtd@lists.infradead.org, vigneshr@ti.com, js07.lee@samsung.com
Subject: Re: [PATCH v3 1/5] mtd: spi-nor: Fix gap in SR block protection locking
Date: Mon, 23 Mar 2020 19:27:13 +0100 [thread overview]
Message-ID: <b9a6d699790e48723489ecbbf1322dfe@walle.cc> (raw)
In-Reply-To: <20200323092430.1466234-2-tudor.ambarus@microchip.com>
Hi,
Am 2020-03-23 10:24, schrieb Tudor.Ambarus@microchip.com:
> From: Tudor Ambarus <tudor.ambarus@microchip.com>
>
> Fix the gap for the SR block protection, the BP bits were set with
> a +1 value than actually needed. This patch does not change the
> behavior of the locking operations, just fixes the protected areas.
So instead of rounding up, it does round down now?
>
> On a 16Mbit flash with 64KByte erase sector, the following changed
> for the lock operation:
>
> Number of blocks | BP2:0 before | BP2:0 now |
> 1 | 010b | 001b |
> 2 | 110b | 010b |
> 3 | 110b | 010b |
> 4 | 100b | 011b |
> 5 | 100b | 011b |
> 6 | 100b | 011b |
> 7 | 100b | 011b |
> 8 | 101b | 100b |
> 9 | 101b | 100b |
> ... | ... | ... |
>
> For the lock operation, if one requests to lock an area that is not
> matching the upper boundary of a BP protected area, we round down
> the total length and lock less than the user requested, in order to
> not lock more than the user actually requested.
I don't know if that is really what a user really want. Because you'd
end up with regions which the user believes are locked but are not.
IMHO if you'd have to make a choice I'd prefer to have the remainder
locked. Not the other way around. Esp. since the user explicitly
express to have a region locked.
-michael
> For the unlock operation, read the number of blocks column as
> "locked all but number of blocks value". On a 16Mbit flash with
> 64KByte erase sector, the following changed for the lock operation:
>
> Number of blocks | BP2:0 before | BP2:0 now |
> 1 | 111b | 101b |
> ... | ... | ... |
> 15 | 111b | 101b |
> 16 | 110b | 101b |
> 17 | 110b | 100b |
> ... | ... | ... |
> 24 | 101b | 100b |
> 25 | 101b | 011b |
> 26 | 101b | 011b |
> 27 | 101b | 011b |
> 28 | 100b | 011b |
> 29 | 100b | 010b |
> 30 | 011b | 010b |
> 31 | 010b | 001b |
> 32 | 000b | 000b |
>
> For the unlock operation, if one requests to unlock an area that is
> not matching the upper boundary of a BP protected area, we round up
> the total length and unlock more than the user actually requested.
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
> drivers/mtd/spi-nor/core.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 877557dbda7f..36660068bc04 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -1654,13 +1654,13 @@ static int spi_nor_sr_lock(struct spi_nor
> *nor, loff_t ofs, uint64_t len)
> /*
> * Need smallest pow such that:
> *
> - * 1 / (2^pow) <= (len / size)
> + * 1 / ((2^pow) - 1) <= (len / size)
> *
> * so (assuming power-of-2 size) we do:
> *
> - * pow = ceil(log2(size / len)) = log2(size) - floor(log2(len))
> + * pow = ceil(log2(size / len)) = log2(size) - floor(log2(len)) + 1
> */
> - pow = ilog2(mtd->size) - ilog2(lock_len);
> + pow = ilog2(mtd->size) - ilog2(lock_len) + 1;
> val = mask - (pow << SR_BP_SHIFT);
> if (val & ~mask)
> return -EINVAL;
> @@ -1739,13 +1739,13 @@ static int spi_nor_sr_unlock(struct spi_nor
> *nor, loff_t ofs, uint64_t len)
> /*
> * Need largest pow such that:
> *
> - * 1 / (2^pow) >= (len / size)
> + * 1 / ((2^pow) - 1) >= (len / size)
> *
> * so (assuming power-of-2 size) we do:
> *
> - * pow = floor(log2(size / len)) = log2(size) - ceil(log2(len))
> + * pow = floor(log2(size / len)) = log2(size) - ceil(log2(len)) + 1
> */
> - pow = ilog2(mtd->size) - order_base_2(lock_len);
> + pow = ilog2(mtd->size) - order_base_2(lock_len) + 1;
> if (lock_len == 0) {
> val = 0; /* fully unlocked */
> } else {
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
next prev parent reply other threads:[~2020-03-23 18:27 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 9:24 [PATCH v3 0/5] mtd: spi-nor: Add SR 4bit block protection support Tudor.Ambarus
2020-03-23 9:24 ` [PATCH v3 1/5] mtd: spi-nor: Fix gap in SR block protection locking Tudor.Ambarus
2020-03-23 18:27 ` Michael Walle [this message]
2020-03-23 19:20 ` Tudor.Ambarus
2020-03-23 19:54 ` Michael Walle
2020-03-23 20:26 ` Tudor.Ambarus
2020-03-23 21:14 ` Michael Walle
2020-03-23 21:30 ` Tudor.Ambarus
2020-03-23 21:33 ` Tudor.Ambarus
2020-03-23 22:35 ` Michael Walle
2020-03-24 5:37 ` Tudor.Ambarus
2020-03-24 3:52 ` Jungseung Lee
2020-03-25 9:44 ` Tudor.Ambarus
2020-03-23 9:24 ` [PATCH v3 2/5] mtd: spi-nor: Set all BP bits to one when lock_len == mtd->size Tudor.Ambarus
2020-03-23 14:08 ` Jungseung Lee
2020-03-23 18:28 ` Michael Walle
2020-03-23 9:24 ` [PATCH v3 3/5] mtd: spi-nor: Add new formula for SR block protection handling Tudor.Ambarus
[not found] ` <000001d600ff$063a8fd0$12afaf70$@samsung.com>
2020-03-23 13:32 ` Jungseung Lee
2020-03-23 9:24 ` [PATCH v3 4/5] mtd: spi-nor: Add SR 4bit block protection support Tudor.Ambarus
2020-03-23 12:43 ` Jungseung Lee
2020-03-23 12:55 ` Tudor.Ambarus
2020-03-23 13:16 ` Jungseung Lee
2020-03-23 18:33 ` Michael Walle
2020-03-23 18:51 ` Tudor.Ambarus
2020-03-23 9:24 ` [PATCH v3 4/5] mtd: spi-nor: Add 4bit SR " Tudor.Ambarus
2020-03-23 9:46 ` Tudor.Ambarus
2020-03-23 9:24 ` [PATCH v3 5/5] mtd: spi-nor: Enable locking for n25q512ax3/n25q512a Tudor.Ambarus
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b9a6d699790e48723489ecbbf1322dfe@walle.cc \
--to=michael@walle.cc \
--cc=Tudor.Ambarus@microchip.com \
--cc=js07.lee@samsung.com \
--cc=linux-mtd@lists.infradead.org \
--cc=vigneshr@ti.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).