linux-kernel - Re: [PATCH 3/3] MTD: spi-nor: add flag to not use sector erase.

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Message-ID: <CAOMqctSn-Ct06tWqSVYPbdoXcFmwrLb1Y9MGvhsSz0gf+fRP3Q@mail.gmail.com>
Date:	Fri, 1 May 2015 09:05:15 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Marek Vasut <marex@...x.de>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"Rafa?? Mi??ecki" <zajec5@...il.com>,
	Alison Chaiken <alison_chaiken@...tor.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"Bean Huo (beanhuo)" <beanhuo@...ron.com>,
	"grmoore@...era.com" <grmoore@...era.com>,
	linux-mtd@...ts.infradead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] MTD: spi-nor: add flag to not use sector erase.

On 1 May 2015 at 01:13, Marek Vasut <marex@...x.de> wrote:
> On Thursday, April 30, 2015 at 11:13:12 PM, Michal Suchanek wrote:
>> The sector size of the flash memory is unclear from datasheet or may
>> possibly vary between chips so add a flag to always use 4k blocks.
>>
>> Currently 4k blocks are always used when possible but in the future
>> somebody might want to do some optimizations with sector erase.
>>
>> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>
> I _think_ you might be able to determine the size, no ?
>
> One way is to ask the vendor, but you can also try something like:
> 1) erase the whole SPI NOR
> 2) overwrite it with zeroes (or ones ? I think it should be all ones after
> erasing).
> 3) Erase sector 0
> 4) Read some 128 KiB back
> 5) Observe what is the difference.
>

I can determine it for this particular chip. However, when the vendor
datasheet says the block is 64/32K it might mean that chips with this
ID can have either block size.

It's a value that we don't use anyway so I just mark it as unknown
here for future reference.

Thanks

Michal
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