[flashrom] [PATCH] 4 byte address mode for Macronix MX25L25735F

[David Hendricks]

On Thu, Mar 31, 2016 at 8:21 AM, Tim Chick <Tim.Chick at mediatek.com> wrote:

> Hi List,
>
>
>
> Flashrom would not detect this chip. When the definition was added,
> everything failed as the chip only supports 4 byte address operation.
>

Interesting - I didn't know such chips existed. The ones I've used have
backwards-compatible commands that support 3-byte addresses. FYI - Some
other high-capacity chips have 4-byte address enable bit in a config
register that will make the usual read/write/erase instructions accept 4
byte addresses. And yet other large chips have alternative instructions
that function the same but only accept a 4-byte address.

The attached patch adds 4 byte address support for 4 byte only chips, as
> determined by the JEDEC flash parameter table, and support for this chip
> specifically.
>
>
>
> I’ve only allowed it to work with the SPI_CONTROLLER_FT2232 controller, as
> that is the only one I have to test.
>
>
>
> I’ve also only ported spi_block_erase_20 – the other block erase functions
> will fail.
>
>
>
> Please let me know what you think!
>

Good stuff! FWIW, I have a work-in-progress patch on chromium.org (
https://chromium-review.googlesource.com/#/c/323359/) for the other types
of high-capacity flash chips. I've tested on a Spansion S25FS256 using
linux_spi and ft2232. It needs a lot of clean-up, but might be of help.
Most of the changes were to convert read/write/erase functions to use
allocated buffers whose length depends on whether we're using a 3- or
4-byte address.

I'll borrow some ideas from your patch as well to support the "4-byte
address only" chips.

-- 
David Hendricks (dhendrix)
Systems Software Engineer, Google Inc.
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