From: Brian Norris <computersforpeace@gmail.com>
To: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org, Marek Vasut <marek.vasut@gmail.com>,
Richard Weinberger <richard@nod.at>,
Zhiqiang Hou <Zhiqiang.Hou@nxp.com>, NeilBrown <neilb@suse.com>,
Boris Brezillon <boris.brezillon@bootlin.com>,
linux-mtd@lists.infradead.org
Subject: Re: [PATCH] mtd: spi-nor: only apply reset hacks to broken hardware
Date: Tue, 7 Aug 2018 12:22:42 -0700 [thread overview]
Message-ID: <20180807192242.GA139259@ban.mtv.corp.google.com> (raw)
In-Reply-To: <20180807183901.GB31722@rob-hp-laptop>
On Tue, Aug 07, 2018 at 12:39:01PM -0600, Rob Herring wrote:
> On Tue, Jul 31, 2018 at 03:35:50PM -0700, Brian Norris wrote:
> > One reason I didn't specifically say something like "not connected", is
> > because IIUC it's actually *possible* to have a robust boot sequence
> > without the RESET# pin -- e.g., if your boot ROM hardcoded a software
> > reset command (just because it's not really standardized doesn't mean
> > one can't do it).
>
> Based on that, then it sounds like you need a specific compatible string
> so you too can know how to s/w reset the device.
We do also support compatible properties for these chips, where needed.
But I don't think that's really needed.
> I guess you are assuming a bootloader didn't leave the flash in an
> unknown addressing state?
For some of these address states (at least, 3-byte vs. 4-byte
addressing), we can still identify the device independently; the READ ID
command works in either mode.
The problem is that a boot ROM is rarely as complex as a Linux driver
and probably can't be updated. And they usually do stupid things anyway.
So *that's* where you need a well-defined entry state for the flash.
Brian
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Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
WARNING: multiple messages have this Message-ID (diff)
From: Brian Norris <computersforpeace@gmail.com>
To: Rob Herring <robh@kernel.org>
Cc: Boris Brezillon <boris.brezillon@bootlin.com>,
NeilBrown <neilb@suse.com>,
devicetree@vger.kernel.org, Richard Weinberger <richard@nod.at>,
Zhiqiang Hou <Zhiqiang.Hou@nxp.com>,
Marek Vasut <marek.vasut@gmail.com>,
linux-mtd@lists.infradead.org
Subject: Re: [PATCH] mtd: spi-nor: only apply reset hacks to broken hardware
Date: Tue, 7 Aug 2018 12:22:42 -0700 [thread overview]
Message-ID: <20180807192242.GA139259@ban.mtv.corp.google.com> (raw)
In-Reply-To: <20180807183901.GB31722@rob-hp-laptop>
On Tue, Aug 07, 2018 at 12:39:01PM -0600, Rob Herring wrote:
> On Tue, Jul 31, 2018 at 03:35:50PM -0700, Brian Norris wrote:
> > One reason I didn't specifically say something like "not connected", is
> > because IIUC it's actually *possible* to have a robust boot sequence
> > without the RESET# pin -- e.g., if your boot ROM hardcoded a software
> > reset command (just because it's not really standardized doesn't mean
> > one can't do it).
>
> Based on that, then it sounds like you need a specific compatible string
> so you too can know how to s/w reset the device.
We do also support compatible properties for these chips, where needed.
But I don't think that's really needed.
> I guess you are assuming a bootloader didn't leave the flash in an
> unknown addressing state?
For some of these address states (at least, 3-byte vs. 4-byte
addressing), we can still identify the device independently; the READ ID
command works in either mode.
The problem is that a boot ROM is rarely as complex as a Linux driver
and probably can't be updated. And they usually do stupid things anyway.
So *that's* where you need a well-defined entry state for the flash.
Brian
next prev parent reply other threads:[~2018-08-07 19:22 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-27 18:33 [PATCH] mtd: spi-nor: only apply reset hacks to broken hardware Brian Norris
2018-07-27 18:33 ` Brian Norris
2018-07-27 19:06 ` Guenter Roeck
2018-07-27 19:06 ` Guenter Roeck
2018-07-27 20:03 ` [PATCH] " Boris Brezillon
2018-07-27 20:03 ` Boris Brezillon
2018-07-31 1:05 ` NeilBrown
2018-07-31 1:05 ` NeilBrown
2018-07-31 20:12 ` Boris Brezillon
2018-07-31 20:12 ` Boris Brezillon
2018-07-31 22:15 ` Marek Vasut
2018-07-31 22:15 ` Marek Vasut
2018-08-01 0:40 ` NeilBrown
2018-08-01 0:40 ` NeilBrown
2018-08-01 8:24 ` Marek Vasut
2018-08-01 8:24 ` Marek Vasut
2018-07-31 22:35 ` Brian Norris
2018-07-31 22:35 ` Brian Norris
2018-08-01 1:06 ` NeilBrown
2018-08-01 1:06 ` NeilBrown
2018-08-07 18:39 ` Rob Herring
2018-08-07 18:39 ` Rob Herring
2018-08-07 19:22 ` Brian Norris [this message]
2018-08-07 19:22 ` Brian Norris
2018-08-01 0:38 ` NeilBrown
2018-08-01 0:38 ` NeilBrown
2018-08-01 7:15 ` Boris Brezillon
2018-08-01 7:15 ` Boris Brezillon
2018-08-07 18:33 ` Rob Herring
2018-08-07 18:33 ` Rob Herring
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