From: Brian Norris <computersforpeace@gmail.com>
To: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
"Rafał Miłecki" <zajec5@gmail.com>,
"Boris Brezillon" <boris.brezillon@free-electrons.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Bayi Cheng" <bayi.cheng@mediatek.com>,
"Marek Vasut" <marex@denx.de>,
"Daniel Kurtz" <djkurtz@chromium.org>
Subject: Re: [PATCH 4/8] mtd: spi-nor: disallow further writes to SR if WP# is low
Date: Fri, 29 Jan 2016 11:23:41 -0800 [thread overview]
Message-ID: <20160129192341.GD19540@google.com> (raw)
In-Reply-To: <CAAEAJfAPbLX9_OOWoUEsVOdUh2DOD+k425u7JkAanjUQxm8MWA@mail.gmail.com>
On Fri, Jan 29, 2016 at 10:22:34AM -0300, Ezequiel Garcia wrote:
> On 28 January 2016 at 16:48, Brian Norris <computersforpeace@gmail.com> wrote:
> > On Thu, Jan 28, 2016 at 04:24:50PM -0300, Ezequiel Garcia wrote:
> >> How about this:
> >>
> >> 1) ioctl(MEMLOCK) the entire flash (SR_SRWD is set)
> >> 2) ioctl(MEMUNLOCK) partially (SW_SRWD keeps set)
> >> 3) ioctl(MEMLOCK) the entire flash again
...
> >> but would (3) be allowed given
> >> SW_SRWD is set?
> >
> > Yes, if /WP=1 (high).
> >
>
> Right. So, after giving some more thought do this, I'd say it might
> make sense to clear SRWD only when unlocking the entire flash. If
> anything else, it would allow a path to disable hardware protection on
> the lock range?
Yes, that sounds fine to me, as it does allow removal of the HW
protection. So one could, for example, do:
0. bring /WP=1 (high)
1. unlock the whole flash
2. bring /WP=0 (low) -- flash is still unlocked
3. allow a one-time relocking of the flash via MEMLOCK
4. no more locking changes
I'll send out v2.
Brian
next prev parent reply other threads:[~2016-01-29 19:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 5:51 [PATCH 0/8] mtd: spi-nor: locking fixes and updates Brian Norris
2016-01-28 5:51 ` [PATCH 1/8] mtd: spi-nor: wait for SR_WIP to clear on initial unlock Brian Norris
2016-01-28 5:51 ` [PATCH 2/8] mtd: spi-nor: guard against underflows in stm_is_locked_sr Brian Norris
2016-01-28 5:51 ` [PATCH 3/8] mtd: spi-nor: silently drop lock/unlock for already locked/unlocked region Brian Norris
2016-01-28 5:51 ` [PATCH 4/8] mtd: spi-nor: disallow further writes to SR if WP# is low Brian Norris
2016-01-28 14:36 ` Ezequiel Garcia
2016-01-28 17:59 ` Brian Norris
2016-01-28 19:24 ` Ezequiel Garcia
2016-01-28 19:48 ` Brian Norris
2016-01-29 13:22 ` Ezequiel Garcia
2016-01-29 19:23 ` Brian Norris [this message]
2016-01-28 5:51 ` [PATCH 5/8] mtd: spi-nor: use BIT() for flash_info flags Brian Norris
2016-01-28 5:51 ` [PATCH 6/8] mtd: spi-nor: add SPI_NOR_HAS_LOCK flag Brian Norris
2016-01-28 5:51 ` [RFC PATCH 7/8] mtd: spi-nor: add TB (Top/Bottom) protect support Brian Norris
2016-01-29 2:36 ` Brian Norris
2016-01-28 5:51 ` [PATCH 8/8] mtd: spi-nor: support lock/unlock for a few Winbond chips Brian Norris
2016-01-28 14:42 ` [PATCH 0/8] mtd: spi-nor: locking fixes and updates Ezequiel Garcia
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