Re: [flashrom] Giving to -i option some real use

[Salvador Eduardo Tropea]

Hi David:

Thanks for your comments.

El 20/04/16 a las 20:42, David Hendricks escribió:
> Hello Salvador,
> Yes, this is a very useful feature - we've had it in the chromiumos 
> branch for a while now :-)
>
> I need to read your implementation. Ours is called "fast-verify" which 
> will read and only verify portions of the flash specified with -i 
> arguments.

What about writes? My problem is that I have a 4 MiB flash and that 
usually need to use 32kB from it.
> It will also restore content surrounding regions (to address Michael's 
> concern) by aligning the bytes read with the erase size. So if you 
> wish to change a small amount of content within an eraseable block, 
> the entire block will be read and erased. The region specified with -i 
> will be written with new content, and the remaining bytes within the 
> block will have the old content restored.
>
> Here's our tree in case you'd like to take a look: 
> https://chromium.googlesource.com/chromiumos/third_party/flashrom/

Thanks for the link.

Regards, SET
> On Tue, Apr 19, 2016 at 10:48 AM, Salvador Eduardo Tropea 
> <[e-mail] > wrote:
> Hi All!
>
> Now I'm using an FPGA board with 4 MiB of flash, was using one
> with 128 kiB. So now the time to read/write/verify the whole
> memory is enough to annoy me ;-)
> So I tried creating a layout like this:
>
> <--
> 00000000:00007e2b fpga
> 00007e2c:003fffff free
> <--
>
> Note: yes only 32300 bytes used, the rest can be used for other
> purposes (0,77%).
>
> And then I used "-i fpga".
> But it didn't help ... flashrom read the 4 MiB twice (one at the
> beggining and another for the verification).
> Looking at the code I found a variable named read_all_first with a
> comment about the lack of implementation.
> So I implemented the needed code to:
> 1) Add a command line option to make it 0 (avoiding the big
> reads). This option can be used only when at least one image is
> indicated with -i
> 2) Skip the big read when read_all_first is 0. Only the regions
> indicated by the user are actually fetched from the memory.
> 3) Same for the verification stage.
>
> Additionally I added a command line option to show the progress,
> very usefull for big memories (and impatient users ;-).
>
> Are these additions desired in the project? If yes: I want to
> discuss the implementation details. If no: I'll just keep them for
> my use.
>
> Regards, SET
>
> -- 
> Ing. Salvador Eduardo Tropea http://utic.inti.gob.ar/
> INTI - Micro y Nanoelectrónica (CMNB) http://www.inti.gob.ar/
> Unidad Técnica Sistemas Inteligentes  Av. General Paz 5445
> Tel: [phone] ext. 6919
> <tel:%28%2B54%2011%29%204724%206300%20ext.%206919>     San Martín
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>
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>
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Giving to -i option some real use

[David Hendricks]

On Thu, Apr 21, 2016 at 1:41 PM, Salvador Eduardo Tropea <
[e-mail]> wrote:
> Hi David:
>
> Thanks for your comments.
>
> El 20/04/16 a las 20:42, David Hendricks escribió:
> > Hello Salvador,
> > Yes, this is a very useful feature - we've had it in the chromiumos
> > branch for a while now :-)
> >
> > I need to read your implementation. Ours is called "fast-verify" which
> > will read and only verify portions of the flash specified with -i arguments.
>
> What about writes? My problem is that I have a 4 MiB flash and that
> usually need to use 32kB from it.

Yes, it works for writes as well. Using your layout file as an example:
00000000:00007e2b fpga
00007e2c:003fffff free

If the eraseblock size is 4KB and you run *"*flashrom -p <programmer> -l
layout -i fpga -w foo.bin --fast-verify*"*, chromium's flashrom will:
1. Detect the flash chip.
2. Parse the -i argument
3. Do a partial read. This is broken into a multiple steps.
3a. Determine the "required_erase_size", for example, 4KB. Right now the
mechanism is crude and chooses the smallest block size that is eraseable.
3b. Align regions that are read based on required_erase_size. 0000 is
already aligned, but 7e2b will be aligned up to 7fff.
3c. Read the aligned region content, which is 0000:7fff instead of
0000:7e2b, into the new content buffer.
4. Copy the new content from the "fpga" region into the new content buffer.
5. Erase and write 0000:7fff
6. Verify from 0000:7fff

Overall it looks pretty similar to what you posted. Here's the original
implementation: https://chromium-review.googlesource.com/#/c/240176/
https://chromium-review.googlesource.com/#/c/240176/4. There are a couple
of follow-up patches as well, in case you're interested.

One more thing to note - Be careful about interactions with the proposed
patch to read the current contents of flash from a file:
https://www.flashrom.org/pipermail/flashrom/2015-December/014034.html.
Specifically, make sure that the aligned offsets are used for reading old
content no matter if the old content is in a flash chip or a file.